Emergent

Automated twits from a workstation, using IFTTT

2012-01-18T11:32:00.002+01:00

When optimizing parameters of stochastic systems you can have hard time predicting when the process is going to end. It would be nice if the workstation itself warns you when it's done, just like Joshua used to give Lightman a call asking him to keep playing Hello, Mr. Falken. You are a hard man to reach. Telephone calls are demodé, anyway. It is much more web 2.0 if the workstation twits you

Mission accomplished

2011-11-24T16:50:00.001+01:00

Rastrigin's benchmark function is far more photogenic than I am I finally got my Master's Degree in computer science, by defending a strongly interdisciplinary thesis about GPGPU-powered parameter estimation in biochemical systems. The method I propose spins around my favourite bio-inspired optimization method – the Particle Swarm Optimization – whose fitness function relies on simulations

Vademecum anti-Renzi

2011-11-02T13:52:00.000+01:00

Matteo Renzi alla "Ruota della Fortuna" Per usare un eufemismo, il sindaco di Firenze Matteo Renzi è una anomalia della politica italiana. Sedicente uomo "di sinistra", è stato eletto nelle fila del Partito Democratico, teoricamente di sinistra anch'esso. Tuttavia, nelle parole e nelle intenzioni, è completamente antitetico allo schieramento di cui, più o meno velatamente, si propone come

RIP dmr

2011-10-13T13:04:00.000+02:00

#include int main() { printf("Goodbye world\n"); printf("%c%c%c Dennis Ritchie\n", 82, 73, 80); return -1; }

Joke of the day

2011-09-23T20:31:00.000+02:00

*knock knock* - Neutrinos! - Who's there? Found here.

Scova l'outlier

2011-09-22T11:08:00.004+02:00

La fregatura di non poter frequentare tutte le lezioni, anche a causa di tediose sovrapposizioni di orario. A tal proposito, sarebbe interessante sviluppare l'organizzazione settimanale degli insegnamenti con gli algoritmi genetici, chissà se ci ha già provato qualcuno... idea che puntualmente ha già avuto qualcun'altro. Anyway, let's call it a day. Avanti tutta verso la tesi! :)

Che bello...

2011-08-24T00:32:00.000+02:00

...quando le cose iniziano a funzionare. Tra qualche anno, son certo che la programmazione GPGPU sarà all'ordine del giorno ed esisteranno efficaci strumenti di supporto allo sviluppo e al debug. Fino ad allora resterà puro autolesionismo.

Teamwork 2

2011-08-17T14:45:00.000+02:00

I took this picture in Corse, while camping at Plage d'Arone. I found these three ants busy in carrying a grape to the nest. They simultaneously attacked the fruit and began to cooperate, by placing at a distance of 120° from each other. Once again, the question is whether we're in front of intelligent behaviour or not. Appearently, this doesn't seem to be the smartest way to achieve the goal

Teamwork

2011-07-15T01:03:00.001+02:00

I'm Hofstadter's huge fan, therefore I use to look at ants as sub-symbolic living metaphors, without any real will except that of the colony. From the collective behaviour, smoothed by evolution, emerges a sharp intelligence. Still, looking at such a stunning demonstration of cooperation, I have hard time considering them like empty shells that simply react to external stimulus. That's a

ARM about to create connectionist's paradise

2011-07-12T13:42:00.003+02:00

ARM is developing a new kind of architecture which is supposed to run a simulation of the human brain. We're not talking about an artificial intelligence here, the project is about the reconstruction of the neuronal topology. In other words, they could prove that connectionist paradigm is right, that is, the brains cause the minds. SpiNNaker, that's the name of the system, is based on a

Emergent ants... the wet way

2011-07-10T17:01:00.001+02:00

Ants never cease to amaze. A group of scientists of the Georgia Institute of Technology studied how groups of ants "link" themselves together forming a self-assembled organic structure that... does not sink! "Even when enough force is applied to submerge it, the raft quickly pops back up undamaged" writes the New Scientist. Appearently, they grip with mandibles, claws and some "adhesive stuff"

La notte della rete

2011-07-05T10:49:00.002+02:00

Online video chat by Ustream La censura della rete è un vecchio tarlo bipartisan italiano e sta arrivando a compimento in questi giorni. La nostra classe dirigente teme internet, perché anarchica e incontrollabile. Un canale i cui contenuti non sono imposti dal palinsesto ma creati dall'utenza. Un sistema in cui non si può sbattere fuori una voce sgradita perché urla la verità, ma con cui

Breakfast time

2011-06-04T17:22:00.000+02:00

AJAX and JSON

2011-05-27T17:39:00.002+02:00

I recently had to develop a kind of "widget" that interrogates a remote server by means of an asynchronous javascript call. The response was a javascript object defined with JSON syntax. Question was: how do I process it? I found many tutorials that use JSONP techniques (weird yet powerful for cross-site execution) but I don't have control on the remote service. Others suggest an external

CUDA, random numbers inside kernels

2011-05-21T22:43:00.005+02:00

Evolutive algorithms have an intrinsic stochastic nature, therefore they make large use of random numbers generators, for instance the C/C++ rand() function. Anyway, when GPGPU comes into play, using random numbers could be tricky. The naive solution of create and pour them into GPU's global memory is a bad idea, because of the huge bandwidth that would be wasted. Therefore, it takes a

On the bioinformatics or: computer science's pillars

2011-05-06T17:04:00.000+02:00

One of the most interesting facets of bioinformatics is that pushes computer science towards its limit. When you deal with huge data sets, a poorly implemented algorithm or the choice of the wrong data structure leads to inevitable failure. Screenshot above shows some information about the costs of a piece of software I'm developing for prof. Besozzi, that executes a slight variation of

Fascinating complexity

2011-05-02T00:41:00.002+02:00

Here we go, another little step towards Master Degree! "Complex systems" is achieved and with full score, thanks to a crowd simulation based on Craig Reynolds' BOIDS and rendered by my own 3D engine "PLT". I love emerging models - as one can easily foresee by reading the name of this blog - and BOIDS is no exception. A few rules and parameters, two constraints and a bit of randomness and we

E anche bioinformatica è archiviata

2011-03-30T01:21:00.001+02:00

Nucleotides bonanza Materia assai affascinante la bioinformatica; mi sono scoperto attratto dalla biologia computazionale e da quello strato di meccanismi e processi naturali che regolano il funzionamento degli esseri viventi. In termini astratti funzioniamo esattamente nella stessa maniera in cui lavorano i computer: il DNA è un linguaggio formale, ed è ammaliante il pensiero che questo codice

Tecnologia e controlli, tredici anni dopo

2011-03-25T11:22:00.004+01:00

Quest'oggi ho verbalizzato l'esame di Progettazione Logica-Digitale, il fratello maggiore della materia che alle superiori veniva chiamata Controlli. I diagrammi dei segnali, so long.. A parte VHDL, che ai "miei tempi" non si faceva, è stato un po' un tuffo nei ricordi, una sorta di ripassone. Ed è esattamente questa la parte interessante: è trascorsa più di una dozzina d'anni ma ho ancora

Radiations in Tokyo, real-time

2011-03-16T17:11:00.000+01:00

Japan is going through a wide spectrum of catastrophes: an impressive earthquake was followed by a terrible tsunami that killed thousands of people, swept away whole villages and destroyed the emergency power generators of Fukushima's cooling system, causing radiation to spread out, even to northern America. Moreover, a vulcano erupted and... there's even a bird flu warning in Chiba. Because of

The BOIDS are back in town!

2011-03-04T13:37:00.004+01:00

During the last lesson of complex systems course, prof. Vizzari showed a crowd simulation based on BOIDS, an intriguing model invented by Craig Reynolds in 1986 that simulates bird flocks, fish schools and all that kind of self-organizing masses of living stuff. The basic model is based on three simple assumptions: each boid moves toward the other flockmates (cohesion) each boid moves away from

A softer way of life

2011-02-11T00:00:00.006+01:00

Soft computing course: completed! A sparkling 30/30 cum laude closes an astonishing and inspiring experience. I chose this course primarly because of simulated annealing and neural networks, for I studied these techniques in a very formal way (cybernetics) and from a philosophic point of view (epistemology). I was interested into a more concrete approach, and I found it here. But there was much

"Impariamo il C", un corso collaborativo

2011-02-09T14:40:00.001+01:00

Qualche settimana fa ho dato via ad un piccolo esperimento sul forum di NGI. Si tratta di un micro-corso di programmazione C di stampo collaborativo: una breve lezione "frontale" discussa con la community. L'approccio che seguo è bottom-up: son voluto partire dalle minuzie (cioé il ferro, quella che viene chiamata architettura dell'elaboratore) e risalire lentamente, introducendo un piccolo

Realizzi di esser stato d'aiuto quando...

2011-02-08T01:30:00.000+01:00

...trovi il tuo blog linkato nelle dispense di due università americane (Central Florida e Central Connecticut). Nice! Il mio post sul workaround per far funzionare Dev-CPP sotto Vista (dio maledica Microsoft per le sue trovate balzane) è diventato un po' il fix de facto in giro per internet, e ha portato più traffico e commenti delle altre centinaia di post che ho realizzato, anche quelle

UNIMIB.IT on Webometrics: new strong performance

2011-02-02T15:15:00.007+01:00

Webometrics publishes, in a biannual fashion, a ranking of universities' websites, produced by a formula that takes into account the size of the site, the number of downloadable documents, the visibility online and the number of google scholar entries. We still have a positive trend and during the latter half we went up 145 positions! Milano-Bicocca's ranking during the years; the lower, the

Il popolo delle coincidenze

2011-01-21T18:23:00.004+01:00

Vorrei condividere una serie di pensieri che ho elucubrato. Forse è tutto un po' dietrologico, ma non sono un tifoso delle coincidenze. La questione Ruby è avvenuta nella notte tra il 27 e il 28 maggio 2010. Il 29 è sabato, il 30 domenica; il lunedì il parlamento non lavora. Il primo giorno utile (cioé il primo giugno) Gasparri e altri amici suoi presentano un emendamento (il 1707) alla legge

Le palle della crisi

2011-01-12T14:34:00.001+01:00

Il grafico quì sopra rappresenta i dati dell'esposizione dei cosidetti PIIGS, aggiornati al 31 dicembre 2010; il pallone più grande siamo noi. Combiniamo questa informazione con l'aver avuto per un anno un Ministro allo Sviluppo occupato ad arredare case a sua insaputa (cioé, a farsi corrompere in cambio di appalti), un altro anno senza averlo proprio (d'altronde il bunga bunga porta via tempo

Ants gone wild!

2010-11-25T18:24:00.010+01:00

I'm currently attending the soft computing course, and it's terrific! I always loved stuff like genetic algorithms, neural networks and such, but I wasn't prepared for particle swarms: it's been a shocking revelation. I really fell in love with them, I adore the wide spectrum of emerging behaviours those bunch of coordinates exhibit and I feel overwhelmed when I think about creative uses of the

Cambia tutto e, in effetti, nulla cambia

2010-11-16T11:13:00.001+01:00

Gerry mi ha fatto scoprire l'archivio storico del quotidiano La Stampa, che copre tutte le pubblicazioni dal 1867 a oggi. Bellissima iniziativa. Per curiosità sono andato a sbirciare la prima pagina del giorno in cui sono nato (il 31 dicembre 1979) per scoprire che, sostanzialmente, andrebbe bene anche oggi. Si parla degli aumenti di benzina, luce, tariffe telefoniche, RCA: si teme l'inflazione

Dell'epistemologia informatica

2010-10-03T02:20:00.004+02:00

Un saggio sul progresso, lettura ideale in spiaggia ...ovvero la scientificità della computer science. Intrigato dal nome veramente insolito per un insegnamento di informatica e da un programma quasi totalmente umanistico, cosa già di per sé rara, ho deciso di inserire questo corso nel piano di studi e si è rivelato una autentica figata. L'esame consiste nel produrre un piccolo saggio su temi

Online Integral Evaluator or: yet another Wolfram|Alpha widgets hello world

2010-07-28T19:21:00.002+02:00

I always loved Mathematica for its symbolic architecture, and that power is now freely available online through the stunning Wolfram|Alpha computational engine. In these days, I'm studying for the third calculus course and I'm using Alpha extensively for definite integration. When I heard 'bout Wolfram's Alpha widget builder I felt natural to develop an on-line integral calculator. It's simple

Milano-Bicocca improves its Webometrics ranking

2010-07-23T10:05:00.001+02:00

Webometrics ranking of world universities shows information about world universities, ranked according to indicators measuring web presence, link visibility, size and number of documents available for download. Since 2004 this chart is done by the Spanish National Research Council, and gets updated every six months. Milan-Bicocca's website has a strongly positive trend as we raised 325

Frenare un'emorrargia di naviganti

2010-07-12T12:03:00.004+02:00

Questo grafico mostra il numero di "rimbalzi" che i visitatori del sito della Bicocca effettuano da una pagina molto particolare: quella delle Facoltà. Purtoppo, per ragioni storiche, gli studenti associano il corso di laurea al concetto di facoltà. Navigando sulla home page, ricercano le informazioni sui corsi cliccando proprio su facoltà e di lì abbandonano il sito affidandosi ai siti

L'usabilità e la scelta del corso di studi

2010-06-28T16:42:00.002+02:00

Come sempre in questo periodo, stiamo lavorando alla pubblicazione dell'offerta didattica del prossimo anno accademico. Poichè il nostro ateneo ha una certa grandezza, l'offerta complessiva è decisamente vasta, organizzata in otto facoltà per un totale di circa 70 corsi di laurea differenti, tra triennali, magistrali, UNA specialistica residua (scienze infermieristiche ed ostetriche), "a ciclo

Aho-Corasick (multiple pattern match) in PHP

2010-06-28T12:12:00.004+02:00

When I started programming Mergifier, my "RSS feeds dispenser", I knew I was going to need some kind of terms filtering. It's useless to take into account the most common words, for they don't bring any information. My initial solution was to split the text into an array of substrings and use array_diff to remove those in my blacklist array. I don't know the asymptotic cost of array_diff

Mergifier: prima alfa

2010-06-11T16:06:00.002+02:00

Mergifier è entrato in funzione! Attualmente si occupa di classificare le notizie di interesse per studenti, docenti e dipendenti. Questi sono i link per sottoscrivere i feed ATOM: studenti docenti dipendenti Il progetto è in una fase embrionale e potrebbe manifestare qualche malfunzionamento; aiutaci segnalando bug o eventuali suggerimenti via email o sul canale facebook! :)

Mergifier: a bayesian RSS filter

2010-06-07T12:23:00.011+02:00

The RSS feed is a popular format used to publish information. XML based, therefore machine-readable, it was thought as a "container" of news from frequently updated web pages. Personally, I love using iGoogle as aggregator to keep, in a single screen, lot of feeds that keep me constantly updated about intersting facts happening around the world. We introduced early this technology on Bicocca's

Just for fun: obfuscated hello world, in C

2010-04-27T17:10:00.001+02:00

main(int argc,char*argv[]){memset(&argc,0,1);char*s[11]={0,-3,4,4,7,-40,15,7,10,4,-4};while(argc<11)printf("%c",s[argc++]+0x48);} What could this code do? =) The reason behind this code is here.

IE - object does not support property or method

2010-04-22T10:07:00.006+02:00

Have you ever experienced the error message I wrote in the title? Are you hitting the walls with your head wondering what the frak it means? This post might be useful to you! I wrote a page that worked seemlessly inside every know browser but Internet Explorers. Well, nothing new under the sun, web developers' work consists mainly in making things run inside that shit. Anyway, I was surprised

Un percettrone per il portalone

2010-04-17T01:18:00.003+02:00

Da un po' di tempo a questa parte mi frulla l'idea di rendere in qualche modo "intelligente" le generazione del primo piano del portale www.unimib.it. Fresco del corso di machine learning del prof. Mauri ho deciso di tentare l'implementazione di un software in grado di imparare dagli esempi - storici e futuri - la mentalità con cui realizziamo giornalmente il primo piano, arrivando un giorno a

Un canale Facebook (ufficiale) per l'Università di Milano-Bicocca

2010-02-08T17:50:00.003+01:00

Da sempre la redazione di unimib.it vede i social networks come un fenomeno importante e rivoluzionario nell'ambito del worldwide web, una notevole opportunità per coinvolgere in prima persona i destinatari del nostro lavoro. Abbiamo già introdotto youtube qualche tempo fa, ora è il momento della rete più imponente al mondo. Facebook, dall'alto delle sue centinaia di milioni di adepti, è da noi

Inline-block and Internet Explorer

2010-01-22T14:26:00.003+01:00

I use to collaborate with the press office of the University. In particular, I was asked to develop a sort of enhanced, multidimensional, collaborative "address book" that they use as a database of journalists. During the development process they often changed requirements, with the result that the project grown way too much. In order to keep the user experience pleasant I did my effort to

Deleting stuff with javascript

2010-01-18T10:33:00.001+01:00

Would you like to clean house with js without messing around with hidden stuff? Piece of cake: document.getElementById("thing_to_delete").parentNode.removeChild(document.getElementById("thing_to_delete")); Yes, it's kinda weird, just like referring to myself as "the son of my father", but it actualy works.

A couple of nice MySQL tricks

2009-12-18T14:36:00.002+01:00

Do you want to transfer records from one table to another, specifying source and destination columns? Piece of cake: INSERT INTO destination ( col1 , col2 ) SELECT col3, col4 FROM source And what if you wish to collapse a subquery in your query results? More complex, but can be easily done with GROUP_CONCAT: SELECT stuff.., GROUP_CONCAT( column_to_sum_up ) AS newname FROM main_source LEFT

Chiarezza, innanzitutto

2009-11-09T10:47:00.000+01:00

error LNK2005: "class std::map,class std::allocator >,class Proiettile *,struct std::less,class std::allocator > >,class std::allocator,class std::allocator > const ,class Proiettile *> > > MappaProiettili" (?MappaProiettili@@3V?$map@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@PAVProiettile@@U?$less@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@V?$allocator@U?

3D collision detection

2009-10-19T23:32:00.005+02:00

3D libraries are conceived as just drawing primitives, and nothing more. That's why graphics programmers are asked to reinvent the wheel several times. One of those wheels is the "world space" partitioning. In particular, the collision detection of meshes. I don't know how serious engines handle it on a per-pixel/vertex basis, but I think they just do miracles. I implemented something simpler

The evolution of parallax

2009-10-09T20:19:00.002+02:00

Once upon a time, videogames were bidimensional, and it was fine. One day, in order to give some depthness to the scene, programmers introduced a technique called parallax scrolling: by moving the elements of the background at different speed, a sense of spatiality and immersivity emerged. The sensation was outstanding for the age, but the drawback was a very high computational cost, that kept

Sprites, animations, and 3D textures

2009-10-06T01:38:00.010+02:00

During the 80s real 3D was just a chimera. Apart some pioneer, embryonic vectorial engine, computer graphics was achieved by using small bitmap images, stored in contiguous memory locations: the sprites. Borrowing from traditional techniques, sprites were animated by drawing the animations in separate images (a classic example) and displaying them in sequence, creating the feeling of dynamism.

Does your shader seamlessly compile, but inexplicably doesn't link?

2009-10-01T20:58:00.005+02:00

Maybe it's due to the GL_MAX_VARYING_FLOATS limit. If you go crazy obtaining the error "Fragment shader(s) failed to link", try reducing your explicit -and implicit- varyings variables. It turns out that, for instance, you cannot combine 8 textures and 8 "blinn-phong light sources" inconsiderately, because if you would like to interpolate textures and light vectors, you end up using (8+8)*4 =

Fixed functionality beats programmable pipeline 10:0?

2009-09-29T17:44:00.002+02:00

Something's terribly wrong somewhere... Blinn-phong shader is wasting all GPU's power! I've done some optimization, but I'm afraid that writing general code, good for all seasons is not the best way to achieve performance. I can't imagine how many compromises serious 3D engines hide under the hood!

Arbitrarily turn static functions into individual threads

2009-09-17T12:33:00.001+02:00

There's a lot of routines that are supposed to run "behind the scene", accomplishing repetitive and constant taks. For instance, in 3D engine the movements should be time-based, so that things behave the same way indipendently from the underlying architecture. We could define a class that "checks the clock" and computes the "amount of changes" to do in the scene. Our observers - that is a

Meshes from points

2009-09-14T17:10:00.003+02:00

It's been an hard job, but an interesting experience. My 3D engine "PLT" now features its own Delaunay triangulation. Now I can turn an arbitrary set of points into a continue, smooth, tridimensional mesh. The algorythm is well explained on Wikipedia, and practically consists in breaking an encompassing triangle in smaller ones, ensuring that every triangle does not "contain" any other vertex.

Δελφοί

2009-09-03T16:00:00.001+02:00

Delphi, l'ombelico del mondo, sede dell'oracolo più famoso di sempre, il posto "in cui chiunque avrebbe fatto il proprio santuario, se non ci avessero pensato prima i Greci". Perché un posto del genere si ritrova come eredità moderna un linguaggio di programmazione insulso? Borland accidenti a te!

The farm of convexity

2009-08-29T14:55:00.014+02:00

I'm working on my first scientific visualization "job" in these days; it's a computational fluid dynamics simulation, which has to be displayed to make some inference.Instead of importing datas into VTK, I loaded them into my 3D framework. And it was a fail, because of three conceptual errors:my engine was written to display polygons; instead, we have ~3000 point samples which have to be

Wavefront .OBJ files & Vertex Buffer Objects

2009-07-22T19:03:00.010+02:00

OBJ files are handy for many reasons:they're text fileswell documentedeasy to parseand many professional softwares can export themThis is why they are so popular as standard files for 3D graphics.Their structure is basically a (long) list of vectors definitions (spatial, normals, texture coordinates, and so on) followed by a (long) list of structures defining faces. What are faces? Faces are

We meet again, dear wheel

2009-07-20T22:57:00.005+02:00

Soon after my experience at CINECA, I took the decision to implement my own 3D engine.I'm not trying to develop the ultimate graphic experience, of course. I just wanna own a set of libraries useful for easily handling and displaying scientific information, without too much effort.Actually, I tried to avoid the huge effort of programming a whole 3D framework from scratch by using OpenSceneGraph;

Nei panni del neo laureato

2009-07-17T17:17:00.004+02:00

A differenza di molti neo-laureati, essendo già un dipendente a tempo indeterminato non ho avuto alcun problema nell'annaspare tra le offerte lavorative radunatemi dagli uffici di job placement subito dopo la proclamazione. Devo anzi ammettere che mi sta procurando un certo diletto osservare la nonchalance delle aziende nel chiedere la Luna in cambio di un tozzo di pane.Nella fattispecie, qualche

100th post!

2009-06-11T11:04:00.007+02:00

Arrivoooooo!! Una bella infornata di OpenGL a livelli massicci... e soprattutto OpenScenegraph! Non vedo l'ora!Spero solo che il mio nuovo Presario arrivi entro domani! Daje mediaworld!

Text mode emacs and python syntax highlighting

2009-05-20T15:34:00.006+02:00

I'm learning python, in order to develop django-powered web applications. The test environment is the my office's mini-server (an old, 900 Mhz Pentium III) with a Debian on it (used for ticketing, backupping stuff and as database/web server supporting internal activities) , without any graphical interface.In order to develop more easily, I apt-got emacs which runs perfectly in text mode. By the

消息! Il portale parla cinese

2009-05-11T20:44:00.004+02:00

Ed eccolo quà. Dopo qualche settimana di fatiche, la localizzazione in cinese di unimib.it è quasi ultimata.Non si tratta di una banale interfaccia a contenuti in italiano/inglese, bensì di una traduzione completa delle informazioni di interesse per la visiting people proveniente dal est asiatico.Tutto, a partire dalla scritta "Università degli Studi di Milano-Bicocca", è stato adattato, finanche

...and the story ends

2009-05-04T13:25:00.019+02:00

56 months have passed since my second enrollment, but this time it worked! I'm finally graduated in computer science with a final score of 99/110.I think this is the time to assess a balance of these years.I'm grown, surely. Grown as a man and programmer. The stage (and thesis) I chose were challenging and helped me understanding who I am and what I could do. I learnt lot from this experience,

Mistificare per principio

2009-04-06T14:10:00.007+02:00

Nessun ritegno pur di far notizia. Il Corriere della Sera sbatte in home page foto di un terremoto turco, spacciandolo per la catastrofe abruzzese. Ma come si fa.. Grazie a Peacemaker (NGI) per la segnalazione.

Fix the MBR, without Windows' permission, in a linux fashioned way

2009-03-30T23:08:00.006+02:00

Il testo completo è disponibile quì: http://aresio.blogspot.com/ I tried to install Kubuntu "Jaunty Jackalope" last sunday.Partitioning worked fine, file were copied without any issue but something went wrong at reboot: GRUB hanged up because of a unintelligible error 18.I googled a bit and it turned out that it's due to the fact that BIOS detects disks in a different way Linux does.So what..? *I

俳句

2009-02-26T09:46:00.006+01:00

Race is over:a long breath.Shivers in the sun.

Ippopotami e nuvole

2009-02-23T11:41:00.011+01:00

Le tags cloud sono un metodo molto efficace per condurre il navigatore attraverso le proprie notizie, informazioni e quant'altro legati ad un preciso argomento, mostrando nel contempo il ventaglio di informazioni disponibili sul sito.Abbiamo deciso quindi di fornire ai visitatori di unimib.it questa possibilità, e in fase di implementazione stanno emergendo alcune considerazioni non

Una nuova pelle

2008-11-18T11:25:00.008+01:00

Dopo quasi un anno di discussioni, pianificazioni, riunioni, litigate, riprogettazioni, ridisegnamenti e sviluppo forsennato, il nuovo portale dell'Università di Milano-Bicocca entra nella sua fase beta.Il sito, per scelta, è per ora visibile ai soli "addetti ai lavori" e quindi rigetta visitatori al di fuori della sottorete 149.132.0.0/16 del campus. In questa fase stiamo provvedendo alla

Image space algorythms, polycount and fps

2008-11-04T23:01:00.006+01:00

Image-space algorythms have one huge benefit: their costs are independent from the overall complexity of the scene. Proof is that putting a ~35k faces model in the middle of the scene does not affect the frames per seconds count.For my experience what seem to drain GPU power are (in ascending order of heaviness):multisampling - useful for sorting-independent transparency, it's not for free and

Expensive state changes

2008-11-02T18:24:00.009+01:00

Everytime you want a primitive to be multi-sampled - in order to convert its alpha values into coverage patterns - you are supposed to explicitly ask for it by enabling GL_SAMPLE_ALPHA_TO_COVERAGE.I thought that keeping this feature enabled for non-translucent primitives was a waste. I was wrong! It's continuosly changing this state that cuts down performances!Therefore, you're going to prefer

La parte peggiore

2008-10-29T12:14:00.006+01:00

La Gelmini ci riporta indietro di vent'anni, ai grembiulini in stile ventennio e alle cazzate sul maestro unico. Ma Tremonti e soci hanno ancor meno pudore, e impongono oggi tagli per miliardi di euro all'Università italiana.L'università pubblica morirà. Naturalmente si potranno cercare finanziamenti dalle aziende, trasformandosi in fondazioni. Ma visto che le aziende storicamente se ne sbattono

Unnatural convolution

2008-10-28T23:07:00.004+01:00

By using a simple convolution filter, with a small 5x5 kernel running on a fragment shader, one can obtain a nicer and softer shadows.This trick was invented by Anirudh Shastry; it's not physically correct, it's prone to artifacts (and that's why I'm gonna use stencils) but it's good to see and pretty fast. Moreover, I didn't have to move the whole rendering pipeline in one shader, which is good.

Don't you know, talking 'bout the convolution it sounds like a whisper

2008-10-28T15:04:00.006+01:00

Hard shadows destroy realism. It's a matter of fact, they look too unnatural, expecially if the rest of the scene appear softly shaded and we overlap a simulated cone of light.Plenty of solutions have been proposed. Furthermore, Nvidia cards are so smart that they automatically apply the percentage closer filtering on shadow maps. ATI cards don't, but proposed a pretty way to implement it (by

Please, someone help us

2008-10-23T15:57:00.007+02:00

Espresso, 23 ottobre 2008«Maroni dovrebbe fare quel che feci io quand’ero ministro dell’Interni (…). Gli universitari? Lasciarli fare. Ritirare le forze di polizia dalle strade e dalle università, infiltrare il movimento con agenti provocatori pronti a tutto, e lasciare che per una decina di giorni i manifestanti devastino i negozi, diano fuoco alle macchine e mettano a ferro e fuoco le città.

Causticity

2008-10-18T00:29:00.008+02:00

A preliminary shot of my "translucency shadow mapping" engine, showing just the "filtrating light" layer. Light illuminates the glass, which projects its texture on the transparent radiation box, which is supposed to project on the wall as well.Seems working, but actually it doesn't.The reason is subtle: the more translucent a surface is, the more it shouldn't stop the light; this means that the

Covert alpha operations

2008-10-16T12:46:00.010+02:00

The screenshot on the left shows my shadow mapping engine rendering two translucent textured surfaces. The first one occludes the spotlight and casts a shadow on the second one which, in turn, casts on the floor and the wall.Through the eye of the needleThe thumbnail looks fine, but a closer look (click it!) reveils many subtle aliasing problems. Fact is that the "alpha to coverage" is just a

Order indipendency

2008-10-15T11:49:00.010+02:00

Translucency and transparency are not trivial in realtime CG.Peaceful ray tracers take their time to throw lines inside and outside objects, while rasterizers have no peace quickly collecting incoming fragments. In order to alpha blend them, they must arrive in a precise order: the farthest, the earliest.This limitation has a deep impact when rendering a scene: you have to sort your objects in

Projective light cone

2008-10-14T15:49:00.003+02:00

Due to its intrinsic nature of texture, the shadow map looks squared.A nice way to improve its appearance is to use the very same coordinates that project the shadow to map an additional bitmap, which simulates the bottom of the light cone produced by the "spotlight".Now it would be cool to simulate the whole light cone by using some kind of volumetric escamotage.

One query, many records, one result

2008-10-07T14:24:00.005+02:00

Sometimes you need to serialize the results of one simple db query. Instead of fetching any single row and appending it to a string, I thought it could be nice (and faster) to delegate the string creation to the database server.I found out there's no explicit way to do it in MySQL, but I created a nice workaround using the group_concat clause:SELECT GROUP_CONCAT (field)FROM tableWHERE index IN (.

Aliasing galore and FBOs

2008-10-01T12:12:00.015+02:00

When you're going to write a 3D shadows engine, your choice is basically restricted to two possibilities: shadow volumes or shadow mapping in one of its flavours.There's no reason to choose shadow mapping but the performances: shadow volumes are more accurate, because a shadow map is a simple texture spread on a scene and used for depth comparisons. It's obvious that texture's detail affects

Pseudo gamma correction

2008-09-26T12:59:00.004+02:00

As several lights add up in the scene, several accumulations happen in the background, flattening average contrast and luminance. In order to have the colorful scene back, we can tweak the accumulation buffer a bit using the GL_MULT function of glAccum API, and passing as multiplication factor the result of 1+γ*numberOfLightSources.Here's a screenshot:compared to the previous images, also with γ=

Put on the red light

2008-09-24T15:30:00.003+02:00

Who said lights are just white? Introducing an almost coherent red light.More then ever, hard shadows and light's cone edge appear too unnatural. Some kind of linear filtering is required here, maybe a PCF for shadows and a bit of blur for cone's boundaries.

N lights are better than one

2008-09-23T16:17:00.004+02:00

Here we go! Accumulation buffers allowed an easy drawing of multiple light sources and relative shadows.The trickiest aspect was the balance of exposition: every light features its accumulation factor and the light contributions are supposed to be under 1, in order to avoid overexposition.It could be a cool effect, anyway. =)

Accumulation buffers

2008-09-21T05:31:00.009+02:00

Shadow mapping is working correctly, but only one (spot!) light at a time.Nature is very different, so engine has to be changed a bit. How can one sum the contributions of several different lights, placed around the scene? Accumulation buffers can do the trick! These supplementary buffers will sum the RGB values of our different takes from any single light and return the final composite

Young 3D engines suffer acne

2008-09-19T10:44:00.005+02:00

As the engine grows up, I refactor some routine. Cleaner code allows me to use some higher level function, like a 3Ds objects loader. And here appears a well-know issue: z-fighting.Even on a surface closest to the light source, you will always discover minor differences in the values associated with the R texture coordinate(...). This can result in "surface acne"(...). You can mitigate this

When shadows and light combine

2008-09-17T14:51:00.003+02:00

Now it's not just primitives and smooth shading! Multitexturing is part of OpenGL since 1.2.1 specification and allows direct textures combining. Putting the shadow map into a separate texture unit (with glActiveTexture) permit us to spread it on our already textured polygons.I don't know if this is the most performant way to achieve a correct result, but it works fine! =)

I can't see the light!

2008-09-09T09:17:00.007+02:00

Now we're talking.And guess what? Nothing was wrong. I tried running the code on my work's ATI x1300 and shadows correctly appeared.I suppose my SIS 650 messes up with alpha testing. Disappointing.And there's another useful information: OpenGL do not work through remote desktop. If you try to connect via terminal services, you'll see just flat shaded polygons. What I can't see is the logic behind

Neverending story

2008-09-08T21:33:00.001+02:00

Something weird is going on here..! Shadows are supposed to be dark! Oo"..at least they appear now!

"Cool and quiet" search box

2008-09-08T16:48:00.006+02:00

It's cool (and a bit web2.0) to have a search box which works as soon as we cease typing, and displays new contents in the very page we're navigating.The concept of "typing ceased" is tricky anyway; it's not cool (and not quiet!) to have the page refreshed soon after the onKeyUp event, because maybe we're still typing the whole word.So, it takes a bit of javascripting:function lookupStuff(flag) {

Reinventing the wheel

2008-09-05T12:17:00.011+02:00

Matrix multiplication is fundamental in computer graphics, expecially when you're dealing with shadow maps and texture projections.Unfortunately, there are no standard functions for matrix multiplication, so it was time for DIY. Here comes my snippet:float* matrixProduct(float* A, float* B) {// we have to allocate space for a 4x4 floats matrixfloat* pointer= (float *) calloc(sizeof(float), 16);//

Reload a page with javascript

2008-09-04T16:08:00.005+02:00

There's a lot of ways for completely reloading a web page via javascript.Only a few permit to clean up any selection done to option forms.Moreover, it turns out that there's only one robust way to do it, without weird confirmations popups (Internet Explorer) or strange behaviours (Firefox):window.location.href=window.location.pathname;Of course, works seemlessly in Chrome.

Work in progress

2008-09-01T15:40:00.006+02:00

The answer to the previous question was: "it does work". I don't know how the framework I'm working on exactly works, but it does strange things with depth buffer.It seems I'm at a good point. Shadow mapping consists in three steps (two, if the video cards supports the GL_ARB_shadow_ambient extension):depth buffer acquisition from light's point of viewa "dim light" rendering from camera's point

Uncomfortable

2008-08-20T18:02:00.004+02:00

Summer and CG don't meet: my warfare computer resists a couple of minutes and then hangs up.I'm working on my trusty notebook now, but the SiS graphics card is resulting a major pain in the ass:warning: OpenGL VBOs not supportedwarning: OpenGL shading language not supportedGod! Any facility that should help me out to work on shadow mapping is not present on this machine. It's like programming in

Cambio di layout...

2008-07-23T15:32:00.005+02:00

...per festeggiare l'archiviazione di algoritmi complementi!E dalla gioia mi son pure arruolato nelle fila dei fans di Dijkstra su Facebook. Evvai!

And the winner is: shadow mapping

2008-07-22T10:27:00.024+02:00

Shadows projection can be tricky. I knew it before beginnig my stage at CNR, and had only confirmations so far: there's a lot of complications you've got to consider before developing. The greatest limit remains, of course, the cost of computations.My first choice and proposal were shadow volumes a là Carmack: definitively intriguing and kind of ideal trait d'union of my universitary life: they

Un bel respiro..

2008-07-04T22:42:00.008+02:00

Thunderbird; 1 mail non letta:«Si comunica che per lo stage "Progettazione e realizzazione di un modulo software in OpenGL per la proiezione di ombre in tempo reale", proposto dal Consiglio Nazionale delle Ricerche - Istituto di Tecnologie Industriali ed Automazione, sei stato selezionato come stagista.Il CNR resta in attesa dell'approvazione e dell'avvio del relativo progetto formativo da parte

Japanese hornets' slaughter

2008-06-23T15:56:00.003+02:00

AdblockMaybe insects exceed even men about cruelty.This is one of the most impressive massacres I've ever seen. Oo"

Bye bye physics

2008-06-11T14:01:00.004+02:00

I must admit, it has been funny. Physics is actually intriguing, challenging and surprising. In addition, Prof. Paganoni knows how to stimulate interest and plant seeds inside others minds.Another step beyond, the light gets brighter, let's run toward advanced algorythms!

SITE "intelligence" group

2008-06-04T10:03:00.004+02:00

"By monitoring terrorist and extremist websites and penetrating password-protected Al Qaeda linked sites, SITE provides a state-of-the-art intelligence service to both practitioners and analysts to understand the adversary." - SITE group.This bunch of pathetic wannabe-hackers found out this CG shot of Washington on a website, and instantly started shouting of Al-Qaeda menace of nuclear bombing: "

lol

2008-05-26T19:55:00.001+02:00

The end of the tunnel

2008-05-26T15:43:00.005+02:00

My first enrolling at University has been in 1998; I was young, stupid and lazy.Freshly out of secondary school, I was conviced that computer science was matter of... computers and programming, but nothing was more far from truth. Reality was so hard-shelled that I quit quite soon.In 2004 I enrolled again. This time - I said to myself - I know what I have to face and the time I'm gonna need to

Crossroads

2008-05-20T14:09:00.005+02:00

And there I am, bouncing in the r>3 bifurcation.Life is certainly a chaotic system, bound to your initial conditions and prone to sudden changes whose conseguences you can not predict.I'm collecting resources, and I'll be forced to quit the aequilibrium condition choosing my path, my future, my work, my specific interests. Sometimes having many interests is a such a disadvantage.