Skeletal Animation

Ok, here we go. Animations.

For implementing animations, I used once again, ThinMatrix’s tutorial.

COLLADA Parsing

The first thing that I had to do is have a way to load the model of the animation into the game. For this, I used the .dae(COLLADA) file format.

To parse it, I used the rapidxml library on github.

Loading the model was the easiest part of the Whole process.

So far so good…

Next up, loading in the animation.

This part wasn’t too complicated either. The only new OpenGL concept was using glVertexAttribIPointer for ints instead of glVertexAttribPointer.

Again, similar to the animation, a ton of things need to work, for this to work.

After having written hundreds of lines of code for loading in the animation and playing it, I decided to test out my luck.

Well that did not work so well did it.

After a day of debugging, I found a problem in my code!!! Ah I was so happy. I forgot to transpose the matrices provided by the COLLADA file!!! That must explain the weird bird-like shape of the model right? I rushed quickly to test it out.

AHHHHHHH

I was fuming. I had no idea what the problem WAS. AT ALL. I was so lost.

The following problem cost me 3 days of my life(obviously I didn’t spend all day those days debugging, only like 1 or hours2).

What was the problem???

I had a struct for representing a vertex attribute

struct attribute
{
	/* attribute number */
	u32 number;	
	/* type of the attribute */		
	u32 t;
	/* size of the attribute */
	GLenum s;
	/* normalized */
	GLenum n;
	/* stride */
	u32 st;
	/* start pointer */
	void * p;
	/* enable divisor or not */
	std::optional<i32> divisor;
};

When I passed this struct into my vertex_layout struct, and into the glVertexAttribIPointer(), I wrote this

glVertexAttribIPointer(attrib.number, attrib.t, attrib.s, attrib.s, attrib.p);

See the problem? There is attrib.s instead of attrib.st for the stride parameter.

Oh my god when I found this I had very mixed feelings. Firstly, the first time I use terrible variable names (n, t, s …), I get cursed with this stupid error.

Secondly, I was upset that I even used these terrible names.

Thirdly, AHHH I was so happy! Finally I found a problem !! Let’s try it out!

Ugh another problem!

Honestly, the way I found the next problem was amazing. I was in the car when I decided to have a few looks back and forth from my code and ThinMatrix’s code. And suddenly I had a epiphany!!!

I had a vec3 and I needed the values to add up to 1. But I was normalizing the vector. AHHH how could I have been so dumb.

Ok I go back to my computer and fix this problem!

Yay it’s taking shape finally!

But what the hell is with his arms??

By this time, school started so I had a lot less time to think about it. Two days after I had this problem, I was really angry. I had no idea what was wrong.

However

After debugging for like an hour, I found the problem. The final problem. The ultimate problem. The problem that has been staring in my face for the whole time.

I was applying a rotation adjustment to every joint (because the Z-axis in blender is up) whereas I had to just put one. In this setup, each joint would have the rotation applied multiple times which is why the arms look like this.

OK Finally I fix the problem and

Ahhhh finally.