I came up with an idea that requires to bind thousands of buffers (Atomic counters and Shader storage ones) to one GLSL program. I first checked if this would make any sense in the limitations of openGL and it seems possible for two reasons :
- On my laptop GL_MAX_ATOMIC_COUNTER_BUFFER_BINDINGS and GL_MAX_SHADER_STORAGE_BUFFER_BINDINGS both are around 32k. So openGL is enclined to let me bind thousands of buffers for one pass.
openGL 4.4 comes up with :
void BindBuffersBase(enum target, uint first, sizei count, const uint *buffers);
On the C code it seems easy, but I have no clue on how to do my shaders. When binding indexed buffers, we are supposed to use :
layout (std430, binding = 0) buffer Objects
{
Object objects[];
};
When binding a couple of buffers it is ok. But in my case :
- I don't know in advance how many buffers will be bound
- Even if I knew, am I supposed to write some lines of code for EACH buffer and define in the layout binding 0, 1, 2, ..., n ?
The question is then : Is there a way to make the shader unaware of the number of buffer that will be bound to it ? Assuming they are ALL containing the same type of data.
Answer :
Thanks to Andon M. Coleman for the quick and clear answers.
First of all, I was wrong to assume my hardware supported thousands of bindings. Rookie mistakes, I took the defined value instead of the runtime one.
On my machine :
- GL_MAX_SHADER_STORAGE_BUFFER_BINDINGS = 96
- GL_MAX_ATOMIC_COUNTER_BUFFER_BINDINGS = 8
- GL_MAX_UNIFORM_BUFFER_BINDINGS = 84
Which is far from what I based my question on.
However, there is a mean to define multiple buffers in the shader :
A
{
B b[];
}
layout (std430, binding = 0) buffer A a[32];
The amount of maximum bindings must be known in advance but those buffers will occupy the bindings from 0 to 31.
