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Normal packing problem with spheremap transform

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Hi. I am trying to pack my view space normals into two float with spheremap transformation. Actually i can pack and unpack them well but, while packing specific vectors - (0,0,1) and (0,0,-1) - , the algorithm is trying to call normalize(0,0). So this is causing a infinite result. Is there any way to solve this without placing some if statements into packing and unpacking functions ? I am using functions from here.

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A year ago, I also have a problem with Crytek's method (don’t remember why).

Now I use a similar method that works well:

float4 CompressNormal(float3 inputNormal)
{
float f = inputNormal.z * 2 + 1;
float g = dot(inputNormal, inputNormal);
float p = sqrt(g + f);
return float4(inputNormal.xy / p * 0.5 + 0.5, 1, 1);
}


float3 SampleNormal(float2 uv, sampler2D textureSampler)
{
float2 normalInformation = tex2Dlod(textureSampler, float4(uv, 0, 0)).xy;
float3 N;
N.xy = -normalInformation * normalInformation + normalInformation;
N.z = -1;
float f = dot(N, float3(1, 1, 0.25));
float m = sqrt(f);
N.xy = (normalInformation * 8 - 4) * m;
N.z = -(1 - 8 * f);
}


I don’t have the Crytek shaders source code in this computer but I think that the use a cool image processing method in the final version. Unfortunately I don’t have time to implement it but with a texture (used to transform the normals to another space) you can implemented easily. I think.

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