CG shader float3 to float pack/unpack functions

Question

I want to use pack/and unpack functions in a CG shader in Unity. They are listed here: http://http.developer.nvidia.com/Cg/pack.html and here: http://http.developer.nvidia.com/Cg/unpack.html

I want to store a float3 (a normal where precision is not of high importance) in a single float (floating-point RenderTexture) and extract the normal in another shader. Therefore, I want to use a combination of pack4_byte and unpack_4byte.

I get shader compiler errors for shader model 2.0, 3.0 and warnings for 4.0 (which are actually the same errors!?)

Do I have to use extensions for that?

I also tried to use DecodeFloatRGBA and EncodeFloatRGBA, but I think that they are meant to be used to pack a float value into RGBA low precision render targets. In my case I tried to use them the other way round, but I seem to get wrong values.

Thanks for your help! :-)

EDIT: I found this Nvidia extension: NV_fragment_program This extension includes pack_4clamp1s and unpack_4clamp1s Maybe this would be the correct way to solve my problem? How would I use such extensions?

Answer 1

Answer by Summit_Peak · Jan 03, 2015 at 11:11 PM

Here's a way to pack a float3 into a float and back:

   public static float f3_f(float3 c) 
   { 
     return dot(round(c * 255), new float3(65536, 256, 1)); 
   }
   public static float3 f_f3(float f) 
   { 
     return frac(f / new float3(16777216, 65536, 256)); 
   }

Here are the corresponding HLSL/CG #defines:

 #define f3_f(c) (dot(round((c) * 255), float3(65536, 256, 1)))
 #define f_f3(f) (frac((f) / float3(16777216, 65536, 256)))

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Summit_Peak · Jan 04, 2015 at 01:54 AM 0

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For float4, see: http://docs.unity3d.com/$$anonymous$$anual/SL-BuiltinIncludes.html float4 EncodeFloatRGBA (float v) - encodes [0..1) range float into RGBA color, for storage in low precision render target. float DecodeFloatRGBA (float4 enc) - decodes RGBA color into a float.

CG shader float3 to float pack/unpack functions

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