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June, 2009:

Status Update

Jun 18th, 2009
by toni.
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Well, well, well…. this time I have screenshots!

Since my last post with screenshots I have discovered many things, the first and most important is that seems that our beloved John Carmack thinks (or thought) that OpenGL was great but that its default behaviors didn’t fit his mental map.

I was following David Henry’s tutorial to load this md5 files. Md5 had great advantages over other file formats, it’s easy, it’s documented and it is in text-form, so it is easy to read and see if you’re doing something wrong. Well, that tutorial is great, honestly, and there’s no “but”. I recommend it to anyone trying to load this file format. Take into account only two minor thing: Quaternion format and triangle orientation. But let’s explain all the process until I obtained a relatively good looking models :)

For some reason I don’t fully understand yet, Id’s quaternions are specified as q = ([x,y,z],-w). That led me to a very strange behaviour on the skinning of my mesh:

More abstract art!

More abstract art!

Why did I obtained such a strange model (even I have to admit I like it!) ? Well, MD5 my friends is a format full of surprises :). When the file specifies the skeletton information it only gives the vector part of the orientation for each bone. This is GOOD, you know, less data to read and well, we’re loading, we can spend as much time as we want, can’t we?.
So we have our vector from the quaternion and we need the scalar part. We know, because someone told us so,  that the quaternions are unitary, so it should be easy, right?

[pmath] w = sqrt(1-x^2-y^2-z^2) [/pmath]

Well, my friends… That would be in the WE_USE_THE_RIGHT_MATHS world, but let’s never forget that we’re dealing with John Carmack here, the man that made Doom and Quake, and probably the only man that can bend maths at will!
So if you ever want to load correctly MD5 quaternions, don’t forget to extract the w component using this:

[pmath] w = -sqrt(1-x^2-y^2-z^2) [/pmath]

Notice the minus sign :D

So once I noticed that (in fact once I re-read the tutorial :P) I corrected my loader and what I obtained was this:

Pink and blue marine

Pink and blue marine

WTF! Yeah i got correct orientations but what the hell were those pink meshes? Over time I’ve been adquiring some good practices that let me spot bugs or strange behaviours quicky, one of those practices could be stated as:

No matter if the material, mesh, sound or whatever asset is wrong, corrupted or unsupported, you MUST provide a fallback so the problems can be easy spotted and fixed.

And that’s what I did with shaders. After a brief discussion with shash about how to dispatch shaders to each material I did a quick and dirty shader dispatcher on the renderer. This function analyzes the material and depending on its properties it assigns a shader to it. Obviously I didn’t take into account all possible material definitions in MD5 material files… in fact it’s a shame but atm I only provide 2 shaders: one for diffuse materials, the other is that magenta shader :). So if the material has a diffuse map I give it a simple (very very simple) shader to texturize. Otherwise I give it the magenta. What’s the advantage of this approach? Well there are 2 main advantages:

  • I am confident that the program won’t crash in case of uncorrect data or unsupported data
  • I will see all geometry EVEN if i don’t have support for a specific material.

So I saw the player model there, it was there! It just have tons of other strange geometry overlapped. So I took a look to the MD5 file model again and I discovered something interesting. There were low poly shadow models there! Amazing! honestly this was totally unexpected, but at least this was easy to fix :) Those models used a material named “shadow” so I just ignored those meshes (my plan is use original material to generate shadowmaps so I didn’t need that geometry anyway).

Ok, so I removed the geometry and what did I obtain?

The smurf marine!

The smurf marine!

YEAH! a blue marine… damn! this was easy tho, the textures were TGA files, those textures are stored in BGRA format so I corrected that and I expected I would get finally the correct marine, right? Well, my journey was not ended… YET :)

Opposite thumbs!

Opposite thumbs!

Ok, something I had noticed when I obtained the blue marine was that the mesh had holes, and as you can see in this screenshot it even had the thumbs… well, reversed! Damn! I couldn’t believe it! :) I checked the depth func and was correct, I was loading the indexes correctly so where was the problem? Ok, shash helped me again (he made a md5 loader years ago and had faced these problem)… well the problem was that triangle order is Clockwise! There’s no problem once you know it, and probably this decision cames from quake 1 ages so I won’t start any kind of war here. I’m trying to become somewhat data agnostic so instead of doing a quick hack I just changed the order at loading time aaaaaaaaand:

This marine has super powers!

This marine has super powers!

Great! I got it! Well, the eyes and mouth look a bit “pinky” but I don’t support that material yet so….

With my loader ready to load new and shiny models I was ready to load… the zFat (doesn’t it has a filesystem like name?)

Almost correct, excepting the tool!

Almost correct, excepting the tool!

Yeah, perhaps is not very noticeable, but the tool is like flat colored, do you see it? Why is this? Well, file formats have plenty of surprises and they’re there, stalking, hiding, waiting to jump over you if you’re amusing. Well, in this case was because textures files in mtr files doesn’t have to have an extension specified. I had  along discussion with Shash regarding if this was or wasn’t a good design decision. Obviously I still think it’s not, but I have to respect others’ point of view. Well, anyway, the format is specified this way, so I had to support it. And after coding a “if the file doesn’t have extension check if it exists for most usual image file extension files” procedure I ended FINALLY with correct models :)

A rotated imp

A rotated imp

zFat with strange pink balls in his hands!

zFat with strange pink balls in his hands!

Hehehe, well, after this I thought it would be nice to have it animated, and that is what I’m working on right now. This time i’ve taken a look to the files looking for usual weirdness, but this time seems that the files are nice enough :) But that is a whole different story and will be told in a different post! until then…

Stay tuned!

Status Update

Jun 11th, 2009
by toni.
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Ok, I don’t have screenshots this time :)

I’ve removed another dependency, this time the affortunate class that was removed from my software wash fboClass. Shadower, the first incarnation (and lucky for all of us now is dead, buried, burnt and… everything) of this engine used several external classes (that is not coded by myself), including lib3ds, glm and fboClass.

fboClass is a wonderful collection of classes and utility functions just to handle FBO, and it was nice to use, but now, with that engine overhauling I thought it would be nice to have my own fbo class, and integrate it with my graphic driver architecture.

Well, one less. At the end I would like to have only SDL and Devil as dependences, well, if I add sound I suppose i will have fmod or openAL too, but that’s another issue :)

The simpler the better

Jun 11th, 2009
by toni.
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You know, graphics is amazing, graphics are interesting, challenging, funny and rewarding. I love reading siggraph papers as much as any other out there, but there’s a thing that I love the most: designing and coding those little helper systems that make your life easier.

Today, for first time in my blog, I will start sharing pieces of code of that pet engine I’m coding at home :) And today’s piece is the tiny Information Item System.

You know, many times you need to get runtime information from the application, information like observer position, memory consumption, frames per second or even runtime profiling information. In previous implementations I had hardcoded that information, that was clumpsy and not very scalable to be honest, so now I had the opportunity to start it all again I decided to do it better, scalable, datadriven and with all those fancy properties that are so cool today.

The idea behind it is very simple, and the system itself is stupidily simple so let’s start explaining it:

I’ve decided that every piece of information I need can fall in one of those 2 categories

  • Text: The information can be retrieved as a string
  • TextTree: The information can be retrieved as a tree of strings

In fact, to be honest, the TextTree was added lately in the design phase, when I realized that profiling could be added to this information system. But having that in mind the design was as simple as it can be.

Every information item would have this properties:

  • There would be only one item for each category (no duplicity)
  • Each item would be capable of gathering all the information needed, process it and format it.

So with that in mind I ended with this UML diagram

Info Item Class Diagram

Info Item Class Diagram

Well, I know, it’s stupidily simple! And of course, at this momment I only need 2 InfoItems (and those are the ones that are implemented).

All this items are stored into a singleton named, let’s be original, InfoItemManager. This is the only place where this info items should be stored.

Info Item Manager

Info Item Manager

Now, how all this thing work?

Pretty easy, on Init time the manager registers all the info items.  Later, on update time InfoItemManager will call to update on each info item, there each info item will process and generate the message that it will return. As I told you, it was easy :)

Ok ok, you will say, the info items have the info, but that doesn’t mean I can use it. Indeed, the information is there, you only need a way to access to it, right?

Each one of the InfoItems have 3 key methods: GetId(),  GetType() and GetInfo().

  • GetId returns the Id type of the info item (FPS, POSTION, OBJECTS and so on)
  • GetType returns if the Info Item returns a single string or a Tree
  • GetInfo returns an union, with a char* in case of being a string or … well, at this momment it only returns that

So here it goes, in case you want to access to, let’s say the Position string you could do something like this

InfoItemManager::GetInstance()->GetInfoItemId(III_POSITION)->GetInfo()


That would return you an InfoItemValue union, that, knowing that III_POSITION returns an string well, you can use it directly to write it down wherever you want.

Well, the code of the manager and the info items can be downloaded here . It’s a bit dirty and such, and it’s exactly how it’s working in my engine. You will notice some weird way to get the position on the InfoItemPosition, and you will see that InfoItemFPS does the actual calculation of the frames per second, but it should be pretty easy to adapt it to any engine (after all they’re only 3 classes!)

Further improvement

Right now this design does exactly what I need, but that doesn’t mean it can’t be improved does it?.  Here are a few:

  • Allowing not returning only strings, but actual data, like vec4.
  • Ensuring that there’s only one instance for each infoitem. That is, in fact pretty easy. Lately, in some of my class hierarchies I’m starting to add an static method named Create in the top most base class. This method takes the type of the object to create and returns an instance of the corresponding class. Well specifiying a Create method in InfoItem we could check if InfoItemManager already has an instance of that method (and it should, Init() method in manager ensures that). If the instance exists we only have to return that instance, otherwise we can create an instance, register it in the Manager and return it.

Well, that’s all, a pretty easy, simple, little example of code. The next one, I’m still thinking if it will be the Graphic Driver or the widgets system.

Stay tuned :)