Question

I am trying to write to a 2-dimensional cudaArray through a surface<void, 2>.
The array has a channel format {32, 32, 0, 0, cudaChannelFormatKindFloat} or to put it more simply, holds vector2s.

I am trying to write a vector2 to the surface at the position indicated by integer coordinates (x, y). The following works well:

// write the float2 vector d to outSurf
surf2Dwrite(d.x, outSurf, x * sizeof(float2), y);
surf2Dwrite(d.y, outSurf, x * sizeof(float2) + sizeof(float), y);

However, if I do

surf2Dwrite(d, outSurf, x * sizeof(float2), y);

only the x component of the vector is being written. What is the reason for this slightly unintuitive behaviour?

Answer 1

I find it hard to believe that any of those surf2Dwrite calls actually do what you think they do. To write a float2 I would use this:

surf2Dwrite<float2>(d, outSurf, x, y);

The x and y arguments are the coordinates on the surface you are writing to and the template parameter tells the call the size of the type being accessed.