Array-shifting (sampling)

Coming from C# background, i’m almost completely unfamiliar with pointers and other unmanaged stuff, which i’m sure what’s tripping me up. I’m doing libnoise type stuff in OpenCL. Simplex was easy, but now I want to do a multi sampled thing including converting a heightmap to a normalmap. Here’s some HLSL that does just that (from a DICE paper):

float3 filterNormal(float2 uv, float texelSize, float texelAspect)
float4 h;
h[0] = heightmap.Sample(bilinearSampler, uv + texelSize*float2( 0,-1)).r * texelAspect;
h[1] = heightmap.Sample(bilinearSampler, uv + texelSize*float2(-1, 0)).r * texelAspect;
h[2] = heightmap.Sample(bilinearSampler, uv + texelSize*float2( 1, 0)).r * texelAspect;
h[3] = heightmap.Sample(bilinearSampler, uv + texelSize*float2( 0, 1)).r * texelAspect;
float3 n;
n.z = h[0] - h[3];
n.x = h[1] - h[2];
n.y = 2;
return normalize(n);

Here’s what I have for in my .cl:

float4 getNormal(float input, int width, int height, int offset)
	float destination;

	int x = get_global_id(0);
	int y = get_global_id(1);

	if((x < width) && (y < height))
		int index = y * width + x;

		destination[index] = input[index];

	return (float4)destination;

First, I can’t write to destination because apparently it’s not an array, and second, if I put the asterisk thinger in there (and thus can write to it), I can’t return destination as a non-asterisky float array.

While this is not what you want to hear, it is what you need to hear: learn C first, and only after you are comfortable with it, try OpenCL.

Nobody jumps directly from crawling to running. We all had to learn how to walk first.

Ok, fair enough. Perhaps it would be an interesting exercise to actually develop the front-end to it in C++ as a learning project, rather than using C#/Luminal (openCL wrapper).