Rendering contents of Shader Storage Buffer Object and Invalid Operation Error

ceebee · September 11, 2012, 1:48pm

I’m trying to use the new OpenGL 4.3 compute shader.

I working with a GL_SHADER_STORAGE_BUFFER which is passed to the compute shader and then I am trying to render the computed results.
However I am getting hung up on drawing the contents of the Shader Storage Buffer as ARRAY_BUFFER

In a nutshell here is the buffer

     glGenBuffers(1, &posSSbo);
glBindBuffer(GL_SHADER_STORAGE_BUFFER, posSSbo);
glBufferData(GL_SHADER_STORAGE_BUFFER, particles * sizeof(struct pos), NULL, GL_STATIC_DRAW);


// init vertex position buffer
    GLint bufMask = GL_MAP_WRITE_BIT|GL_MAP_INVALIDATE_BUFFER_BIT;


struct pos *points = (struct pos *)glMapBufferRange(GL_SHADER_STORAGE_BUFFER, 0, particles * sizeof(struct pos), bufMask);
for (auto i=0;i&lt;particles;i++) {
    points[i].x = (0.5f-float(std::rand())/RAND_MAX) * 5.0f + 0.0f;
    points[i].y = (0.5f-float(std::rand())/RAND_MAX) * 5.0f + 20.0f;
    points[i].z = (0.5f-float(std::rand())/RAND_MAX) * 5.0f + 0.0f;
    points[i].w = 1.0f;
}
glUnmapBuffer(GL_SHADER_STORAGE_BUFFER);

… call compute shader…

… try to draw …
glMemoryBarrier(GL_VERTEX_ATTRIB_ARRAY_BARRIER_BIT);
glBindBuffer( GL_ARRAY_BUFFER, posSSbo );
glVertexAttribPointer(0,4,GL_FLOAT,GL_FALSE,4*sizeof(GLfloat),(void *)0 ); <– Get Invalid Operation Here

I have looked at both Mike Bailey’s Sigragph 2012 notes: ComputeShader_2pp.pdf
and the spec for Shader Storage Buffer object http://www.opengl.org/registry/specs/ARB/shader_storage_buffer_object.txt and they have similar code. In fact the above code is copied from Mike Bailey’s notes.

I have seen comments that you need to have a bound ARRAY_BUFFER (which makes sense) to prevent an Invalid Operation but I am clueless as to why I am getting this error.

Any ideas or comments would be really appreciated.

Craig