Question

I am creating an OpenGL texture like this:

glGenTextures( 1, &boardTex );
glBindTexture( GL_TEXTURE_2D, boardTex );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA32F, width, height, 0, GL_RGBA, GL_FLOAT, NULL);

I get a handle at board so I assume the texture’s been successfully created. I want to share this texture with CUDA so I register and map the resource:

cudaGLSetGLDevice(0);
cudaGraphicsGLRegisterImage( &boardImage, boardTex, GL_TEXTURE_2D, cudaGraphicsMapFlagsNone );
cudaGraphicsMapResources( 1, &boardImage, 0 );

Then I try to get the mapped pointer like this:

float4* mappedPointer;
size_t mappedSize;
cudaGraphicsResourceGetMappedPointer( (void**)&mappedPointer, &mappedSize, boardImage );

Unfortunately this call returns an error and refuses to work. I made sure the texture wasn’t bound in OpenGL context just in case. Still not working. cudaGetErrorString yields “unknown error” so I’m pretty stuck here. I’d appreciate any ideas.

Answer 1

Okay, I found this out myself:

cudaGraphicsSubResourceGetMappedArray (&array, resource, 0, 0); returns a cudaArray to work with. I have yet to wrap my mind around how cudaArrays work (and I might end up using PBOs) but at least it’s not crashing.

Edit:

From the CUDA Reference Guide entry for cudaGraphicsResourceGetMappedPointer():

If resource is not a buffer then it cannot be accessed via a pointer
and cudaErrorUnknown is returned.

From the CUDA Reference Guide entry for cudaGraphicsSubResourceGetMappedArray():

If resource is not a texture then it cannot be accessed via an array
and cudaErrorUnknown is returned.

In other words, use GetMappedPointer for mapped buffer objects. Use GetMappedArray for mapped texture objects.