I'm using a compute shader, and I can't seem to get the right values back

Vulkan
1

I am just using a compute shader to get the transformed vertex positions of a skinned model and. It seems like there is something going on because the values change when I change the model uniform. I have normalized the bone weights of the vertices then get a copy them from the parts I need and take the information out except the position, bone IDs and weights.

float scale = 1;
//for (float half = 1; half > pow(2, -26); half /= 2) {
    modelCompTrans.model =glm::translate(glm::mat4(1), glm::vec3(0, 0, 0)) * glm::scale(glm::mat4(1), glm::vec3(scale, scale, scale));
    modelMems.CopyToInputStorageBuffer(0, modverts.data());
    modelMems.CopyToInputUniformBuffer(2, &modelCompTrans);
    uint32_t axisnum = (uint32_t)ceil((float)modverts.size() / 1000.0);
    modelSim.bind(axisnum, 1, 1);
    modelSim.compute();
    std::vector<glm::vec4> outVerts;
    outVerts.resize(modSize);
    modelMems.CopyFromOutputBuffer(1, outVerts.data());

If I use a translation where X = 1

modverts[i].position.x - outVerts[i].x / outVerts[i].w

should be equal to 1
This is my compute shader:

#version 450

layout(local_size_x = 1000, local_size_y = 1, local_size_z = 1) in;

struct disVert {
    vec4 position;
    int boneIds[16];
    float weights[16];
};

layout(std430, binding = 0) buffer inputBuffer {
    disVert valuesIn[];
};

layout(std430, binding = 1) buffer outputBuffer {
    vec4 outPosition[];
};

layout(binding = 2) uniform TRANS{
	mat4 model;
	int maxNum;
    int padd[3];
	mat4 bonematrices[160];
}trans;

void main(){
	uint index = gl_LocalInvocationID.x + gl_WorkGroupID.x * 1000;
	if (index < trans.maxNum){
		vec4 totalPosition = vec4(0.0f);
		bool cont = true;
		int i = 0;
		bool nhasBone = true;
		while(i < 16 && cont){
			if (valuesIn[index].boneIds[i] == -1){
				cont = false;
			}else{
				nhasBone = false;
				vec4 localPosition = trans.bonematrices[valuesIn[index].boneIds[i]] * valuesIn[index].position;
				totalPosition += localPosition * valuesIn[index].weights[i];
			}
			i++;
		}
		if (nhasBone){
			outPosition[index] = trans.model * valuesIn[index].position;
		}else{
			outPosition[index] = trans.model * totalPosition;
		}
	}
}
2

I have created a sanity check:

#version 450

layout(local_size_x = 1000, local_size_y = 1, local_size_z = 1) in;

struct disVert {
    vec4 position;
    int boneIds[16];
    float weights[16];
};

layout(std430, binding = 0) buffer inputBuffer {
    disVert valuesIn[];
};

layout(std430, binding = 1) buffer outputBuffer {
    vec4 outPosition[];
};

layout(binding = 2) uniform TRANS{
	mat4 model;
	int maxNum;
    int padd[3];
	mat4 bonematrices[160];
}trans;

void main(){
	uint index = gl_GlobalInvocationID.x;
	if (index < trans.maxNum)
        outPosition[index] = trans.model * valuesIn[index].position;
}

everything seems to work here

3

I found out the problem. It was a memory alignment issue I had a struct like this:

struct alignas(16) CompTrans {
	glm::mat4 model;
	int max;
	int padd[3];
	glm::mat4 boneMatrices[160];	
};

If it were aligned properly it should have a size of 10320 161 * 64 + 16 but it was actually larger so what I did was change it to:

struct alignas(16) CompTrans {
	glm::mat4 model;	
	glm::mat4 boneMatrices[160];
	uint32_t max;
	uint32_t padd[3];
};