Code from https://retroscience.net/ray-tracing-with-cuda.html#rule-1---memory-access

grid.c

int threadsPerBlock = blockDim.x * blockDim.y * blockDim.z;
int blocksPerGrid = gridDim.x * gridDim.y * gridDim.z;
int threadPositionInBlock = threadIdx.x +
	blockDim.x * threadIdx.y +
	blockDim.x * blockDim.y * threadIdx.z;
int blockPosInGrid = blockIdx.x +
	gridDim.x * blockIdx.y +
	gridDim.x * gridDim.y * blockIdx.z;