Chinese Watercolor Shader Implementation (HLSL)

Tool : ATI Rendermonkey

Language: HLSL

Concept:

First, I use 3D-Based edge detection. Basically, all I need is the dot production of view-to-vertex vector and the vertex normal. Then, if the dot production is bigger than x (x can be thought as the ink width or the angle between the normal and view vector), I draw black texture on it. If the dot production smaller than x, I draw another texture on it.

Key Code:

VS_OUTPUT vs_main( VS_INPUT Input)

{

   VS_OUTPUT Output;

   

   float3 Nrm = normalize(Input.Normal);

   float3 ViewVec = normalize(Input.Position - viewPos);

   Output.edge = dot(Nrm, ViewVec);

   Output.Position = mul( Input.Position, mul(mul(view,projection),world));

   Output.Normal = Nrm;

   return( Output );

}

float4 ps_main(float edge:TEXCOORD0, float3 N1: TEXCOORD1) : COLOR0

{   

    float4 color; 

    float absV = abs(edge);

    if(absV

   {

      float2 findColor = float2(absV*2.5f, N1.x/2.0f+N1.y/2.0f);

      color = tex2D(Texture1, findColor);

   }

   else

   {

     float2 findColor = float2((1-absV)*1.666f, N1.x/2.0f+0.5f);

      color = tex2D(Texture0, 1-findColor);

   }

   return color;

}   

Here is another test: Ink Shading + Lambert Shading