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ShaderSnippets

Why reinvent the wheel? There're some handy little functions for the everyday HLSL writer. Please add your snippets in this wiki page.

General snippets

get clipping planes of a Perspective Projection

VertexShader snippets

apply rotation to vertices via texture

PixelShader snippets for Image processing

invert
contrast
black&white
lumakey
scene alpha
working alpha channel in 3d

General snippets

get clipping planes of a Perspective Projection

float4x4 tPI: PROJECTIONINVERSE;
float FarPlane = 1 / (tPI[2][3] + tPI[3][3]);
float NearPlane = 1 / distance(tPI[2][3], tPI[3][3]);

VertexShader snippets

apply rotation to vertices via texture

rotation function:

float4x4 Vrotate(float rotX, 
         float rotY, 
         float rotZ)
  {
   rotX *= TwoPi;
   rotY *= TwoPi;
   rotZ *= TwoPi;
   float sx = sin(rotX);
   float cx = cos(rotX);
   float sy = sin(rotY);
   float cy = cos(rotY);
   float sz = sin(rotZ);
   float cz = cos(rotZ);
 
   return float4x4( cz*cy+sz*sx*sy, sz*cx, cz*-sy+sz*sx*cy, 0,
                   -sz*cy+cz*sx*sy, cz*cx, sz*sy+cz*sx*cy , 0,
                    cx * sy       ,-sx   , cx * cy        , 0,
                    0             , 0    , 0              , 1);
  }

use the function like this:

PosO = mul(PosO, Vrotate(Sampler.r, Sampler.g, Sampler.b));
NormO = mul(NormO, Vrotate(Sampler.r, Sampler.g, Sampler.b));

Sampler.rgb are the corresponding values from the texture

PixelShader snippets for Image processing

invert

rgb-inversion

col.rgb = 1 - col.rgb;

contrast

col.rgb = ((col.rgb - 0.5) * var) + 0.5;

if var > 1, the contrast is greater. var = 0 gives a grey picture
The 0.5 can be replaced with a variable to give a gamma or centre
point for the contrast as well, for more fine tuning...

black&white

const float4 lumcoeff = {0.299, 0.587, 0.114, 0};
col = dot(col, lumcoeff);

the dot product of the color (col) and the luminace coefficients results in a correct b&w image

lumakey

const float4 lumcoeff = {0.299, 0.587, 0.114, 0};
float luma = length(dot(col, lumcoeff));
col.a = step(var, luma);

var is the keying amount. the rest works like the b&w conversion.

scene alpha

return(tex2D(Samp, float2(IN.TexCd.xy)).wwww);

Texture input must be in A8R8G8B8 format.

working alpha channel in 3d

needs 2 passes so connect an iobox with 2 rows to the pass pin and fill it with 0,1

technique workingalpha
{
    pass P0
    {
        VertexShader = compile vs_1_0 VS();
        PixelShader  = compile ps_2_0 PS();
        AlphaBlendEnable = false;
 
        AlphaTestEnable = true;
        AlphaFunc = Greater;
        AlphaRef = 245;
 
        ZEnable = true;
        ZWriteEnable = true;
 
        CullMode = None;
    }
    pass P1
    {
        VertexShader = compile vs_1_0 VS();
        PixelShader  = compile ps_2_0 PS();
        AlphaBlendEnable = true;
        SrcBlend = SrcAlpha;
        DestBlend = InvSrcAlpha;
 
        AlphaTestEnable = true;
        AlphaFunc = LessEqual;
        AlphaRef = 245;
 
        ZEnable = true;
        ZWriteEnable = false;
 
        CullMode = None;
    }
}