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brtnrdr

Building Cubemap lookup tables

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brtnrdr    202
I'm trying to build lookup tables for each face of a cubemap. I loop over the texels of a 2D texture and have to determine the 3D vector that would index that texel in the cubemap (there is an index that determines what face is currently being worked on. I have looked at the directx documentation and what I have come up with is shown below. Can someone just confirm this makes sense as my program is not working. Here, face follows the directx convention, i.e. face = 0 == xpos, face = 1 == xneg, face = 2 == ypos, face = 3 == yneg, face = 4 == zpos and face = 5 == zneg.
void cubeCoord(D3DXVECTOR3* res, D3DXVECTOR2* tex, int face)
{
	D3DXVECTOR3 temp;

	switch(face) {
	case 0:
		temp = D3DXVECTOR3(1.f, -tex->y, -tex->x);
		break;
	case 1:
		temp = D3DXVECTOR3(-1.f, -tex->y, tex->x);
		break;
	case 2:
		temp = D3DXVECTOR3(tex->x, 1.f, tex->y);
		break;
	case 3:
		temp = D3DXVECTOR3(tex->x, -1.f, -tex->y);
		break;
	case 4:
		temp = D3DXVECTOR3(tex->x, -tex->y, 1.f);
		break;
	case 5:
		temp = D3DXVECTOR3(-tex->x, -tex->y, -1.f);
		break;
	}

	D3DXVec3Normalize(&temp, &temp);
	
	res->x = temp.x;
	res->y = temp.y;
	res->z = temp.z;
	
}

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SimmerD    1210
Is it a fp16 or fp32 cubemap? If not, you will need to convert into d3d colors instead of outputting a d3dxvector3...

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brtnrdr    202
Hi,

Thanks for the reply, but I'm not storing vectors in the cubemap. I'm trying to store the spherical harmonic basis functions sampled at the texels of a cubemap. In order to evaluate the functions at a texel I need the 3-vector from the origin to the texel. In order to get this I am iterating over a 2D grid (corresponding to a face of the cubemap) and based on an index (corresponding to one of the six faces) I am calculating the vector used to sample the cubemap (this is the code above that I'm asking about).

I can post more of the code if people need to see more to understand what is going on.

Thank you.

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