How to update array of matrices to glsl shader - c++

Question

I'm currently working with skeletal animation and I'm really close to getting it working. Currently, I have a struct that has a matrix with 100 spots ( this is so that I can max have 100 joints ) like so :
struct skelShader {
glm::mat4 currentJointTrans[100];
};
The struct should be binded in the shader, I've done it like this:
glGenBuffers(1, &sksBuff);
glBindBuffer(GL_UNIFORM_BUFFER, sksBuff);
// bind buffer to work further with it...
// allocate memory for the buffer in the GPU
glBufferData(GL_UNIFORM_BUFFER, sizeof(skelShader), NULL, GL_STATIC_DRAW);
// because we hard-coded "binding=3" in the shader code we can do this:
// bind Uniform Buffer to binding point 3 (without caring about index of UBO)
glBindBufferBase(GL_UNIFORM_BUFFER, 4, sksBuff);
// good practice, unbind buffer
glBindBuffer(GL_UNIFORM_BUFFER, 0);
sksBuff is just an GLuint.
I fill this array with new values every render/frame that goes by, these values are the new transformations for the joints. I do it like this:
for (int i = 0; i < skeleton.size(); i++) {
globalSkelInfo.currentJointTrans[i] = skeleton[i]->transformMat[currentFrame - 1] * skeleton[i]->globalBindPosMat;
}
This is working correctly for the root joint, but the rest of the joints/mesh remains in bind pose. The problem should be located in where I update the array. Currently I do it like this in the render function after I've done the multiplication for each joint:
for (int i = 0; i < skeleton.size(); i++) {
glUniformMatrix4fv(glGetUniformLocation(aShaderProgram, ("currentJointTrans[" + std::to_string(i) + "]").c_str()),
1, GL_FALSE, glm::value_ptr(globalSkelInfo.currentJointTrans[i]));
}
After this I draw. The root joints values seem to be moving correctly, but the rest of the mesh is in bindpose and doesn't move. In the Vertex Shader I try to update the matrix like this:
#version 440
const int maxJoints = 100;
const int maxWeights = 4;
layout(location = 0) in vec3 vertex_position;
layout(location = 1) in vec2 vertex_UV;
layout(location = 2) in vec3 vertex_normal;
layout(location = 3) in vec4 vertex_weight;
layout(location = 4) in ivec4 vertex_controllers;
out vec2 outUVs;
out vec3 outNorm;
layout(binding = 3 , std140) uniform uniformBlock
{
vec3 camPos;
mat4 world;
mat4 LookAt;
mat4 projection;
mat4 MVP;
};
layout(binding = 4 , std140) uniform animationStruct
{
mat4 currentJointTrans[maxJoints];
};
void main() {
vec4 finalModelPos = vec4(0.0);
vec4 finalNormal = vec4(0.0);
for (int i = 0; i < 4; i++) {
mat4 jointTrans = currentJointTrans[vertex_controllers[i]];
vec4 posePos = jointTrans * vec4(vertex_position, 1.0);
finalModelPos += posePos * vertex_weight[i];
vec4 worldNormal = jointTrans * vec4(vertex_normal, 0.0);
finalNormal += worldNormal * vertex_weight[i];
}
gl_Position = MVP * finalModelPos;
outNorm = finalNormal.xyz;
outUVs = vertex_UV;
}
My theory is that the updating of the struct skelShader with my currentJointTrans array is incorrect. Any tips on how I should do this instead?

Answer 1

glUniform* calls cannot set data in uniform buffers. Indeed, the whole point of uniform buffers is that the uniform data comes from a buffer object. That's why you had to create one.
So if you want to set the uniform data for a uniform block, you set that data into the buffer object.