I am trying to make a skeletal animation using OpenGL using my own FBX SDK binary files.
What I've done is that I'm reading values from an FBX file and writing out the values I need to an binary file for another program. The info I get for the animation is the Inverse Bind pose, which vertices the joints are controlling and how much weight/influence the vertex has for each joint. I also baked the animation so that the set keyframes are on each frame in Maya, to keep it simple for now. I then read the translation,rotation and scale for each join every frame. I write out all these values in binary and read them in another program, and the values that I read are correct when I compare it to the program that reads the values.
To update the animation I've done a simple for loop that goes through all the joints and updates the weight values and makes the new transform pose like so:
for (int i = 0; i < skeleton.size(); i++) {
for (int k = 0; k < 4; k++) {
globalSkelInfo.indexPos[k] = skeleton[i]->indexPos[k];
globalSkelInfo.indexInfluence[k] = skeleton[i]->indexInfluence[k];
}
globalSkelInfo.currentJointTrans[i] = skeleton[i]->transformMat[currentFrame] * skeleton[i]->globalBindPosMat;
}
the struct skelShader is a struct I send to the GPU, it has the values that should be needed for the animation to work:
struct skelShader {
int indexPos[4];
float indexInfluence[4];
glm::mat4 currentJointTrans[100];
};
This is my vertex shader:
void main() {
vec4 finalModelPos = vec4(0.0);
vec4 finalNormal = vec4(0.0);
for (int i = 0; i < 4; i++) {
mat4 jointTrans = currentJointTrans[indexPos[i]];
vec4 posePos = jointTrans * vec4(vertex_position, 1.0);
finalModelPos += posePos * indexInfluence[i];
vec4 worldNormal = jointTrans * vec4(vertex_normal, 0.0);
finalNormal += worldNormal * indexInfluence[i];
}
gl_Position = MVP * finalModelPos;
outNorm = finalNormal.xyz;
outUVs = vertex_UV;
}
If I'm not using any animation techniques, the mesh is correct.
However, when I apply this code to the render function, together with the code that increases and resets the current keyframe, the mesh looks like this:
The mesh is moving slightly so it does have some movement. I've tried changing around the matrix multiplication for the currentJointTrans, so that the bindPose goes first, but it only makes the mesh disappear. Does anyone know what the problem could be?
If needed, I can send more code and/or debugging values of the matrices that's needed.
This is how the model looks without the animation from the update function and vertex shader (Ignore the texture and the tiny cube under the model):
