I am trying to use a frame buffer for object picking and trying to use stbi_write_png to see what i'm rendering as this frame buffer is not going to be rendered to the screen. I want to use unsigned ints to determine the object id. This is the frame buffer definition, I do check if the frame buffer is valid.
glGenFramebuffers(1, &frameBufferObject);
glBindFramebuffer(GL_FRAMEBUFFER, frameBufferObject);
glGenTextures(1, &frameBufferTexture);
glBindTexture(GL_TEXTURE_2D, frameBufferTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB32UI, width, height, 0, GL_RGB_INTEGER, GL_UNSIGNED_INT, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, frameBufferTexture, 0);
This is the render to the frame buffer and then save the image
glBindFramebuffer(GL_DRAW_FRAMEBUFFER, frameBufferObject);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
renderScene();
unsigned int* pixelData = new unsigned int[width * height * 3];
glReadPixels(0, 0, width, height, GL_RGB_INTEGER, GL_UNSIGNED_INT, pixelData);
unsigned char* pngData = new unsigned char[width * height * 3];
for (u64 i = 0; i < width * height; i++) {
pngData[i * 3] = pixelData[i*3] & 0xff;
pngData[i * 3 + 1] = pixelData[i * 3 + 1] & 0xff;
pngData[i * 3 + 2] = pixelData[i * 3 + 2] & 0xff;
}
stbi_write_png(path, width, height, 3, data, 0)
delete[] pixelData;
delete[] pngData;
Render Scene is this
bindShader();
glUniformMatrix4fv(projectionLocation, 1, GL_FALSE, projection);
glUniformMatrix4fv(viewLocation, 1, GL_FALSE, view);
glBindVertexArray(vertexArrayObject);
glDrawArrays(GL_POINTS, 0, amountObjects);
Vertex Shader
#version 330 core
layout(location=0)in vec3 location;
uniform mat4 projection;
uniform mat4 view;
mat4 getTranslationModel(vec3 loc){
mat4 toRet=mat4(1.f);//Init to identity matrix
toRet[3]=vec4(loc,1.0);//Set the translation params
return toRet;
}
void main(){
mat4 model=getTranslationModel(location);
gl_Position=projection*view*model*vec4(0,0,0,1);
}
Geometry Shader
#version 330 core
layout(points) in;
layout(triangle_strip, max_vertices=4) out;
const vec4 halfX=vec4(0.75,0,0,0);
const vec4 halfY=vec4(0,0.75,0,0);
void main(){
vec4 loc=gl_in[0].gl_Position;
//Top Left
gl_Position=loc-halfX+halfY;
EmitVertex();
//Bottom Left
gl_Position=loc-halfX-halfY;
EmitVertex();
//Top Right
gl_Position=loc+halfX+halfY;
EmitVertex();
//Bottom Right
gl_Position=loc+halfX-halfY;
EmitVertex();
EndPrimitive();
}
Fragment Shader
#version 330 core
layout(location=0)out uvec3 FragColour;
void main(){
FragColour=uvec3(255,0,0);
}
When the image is created, it's just a black image. The goal is to see a red square as if I can see the red square, I can easily replace that number with an object id.
