Labyrinthica features cel shaded graphics.
On the most simplistic level shading is taking a color value from the surface’s texture and multiply it by an intensity scalar, which is based on how the light source affect the surface.
The scalar value is usually a floating point that goes from 0 to an unbounded positive number.
In cel shading, we want to quantize this scalar into non continuous values.
The general cel shader is a piece of code that quantize the intensity scalar. The parameters to the function are:
a – The original intensity scalar.
n – The number of quantization cels.
f – The cel transaction factor.
Return value = The quantized intensity scalar.
There are actually n+1 cel levels, the additional cel level is for intensity values greater than 1.
I will not explain the shader in details. I hope the code will be clear enough for people to understand on their own. Though I could explain it in more details if there will be a demand.
A few screen shots with different parameter values:
Cel shade(n=2, f=0.8)
Cel shade (n=2, f=0.5)
Cel shade (n=3, f=0.8)
One last word before the code. My older CelShade function got only one parameter, the intensity.
I made the new CelShade with 3 paramters, but then I saw I would need to update every place I called the function.
Instead I have created GeneralCelShade as the function with 3 parameters, and replaced the old function with a function that calls GeneralCelShade with appropriate parameters.
The bonus is that now changing the parameters in only one place affect the whole game/shaders.
Very simple, yet very useful.
float
Quantize (float a, float n)
{
return floor(a*n)+1.;
}
float
Trunc (float c, float f)
{
return (c>f)*(c-f)/(1.-f);
}
float
SubCel (float a, float n, float f)
{
float q = Quantize(a, n);
float c = q-a*n;
return (q>1.)*Trunc(c, f)/n;
}
float
GeneralCelShade (float a, float n, float f)
{
float c = Quantize(a, n)/n;
a = c-SubCel (a, n, f);
a = min (a, (n+1)/n)*(3./2.)/((n+1)/n);
return a;
}
float
CelShade (float a)
{
return GeneralCelShade (a, 2, 0.8);
}
