Не об этом ли речь идет?
Код AS3:
depthPassFragmentShader.assemble(Context3DProgramType.FRAGMENT,
"div ft0 v0.z fc0.x \n" + //FT0 Ranges From 0 to 1 and its the depth of the pixel from the light
"mul ft0 ft0 fc1 \n" + //FT0 = [FT0,255*FT0,(255^2)*FT0,(255^3)*FT0] for encoding 32 bit floating point into RGBA
"frc ft0 ft0 \n" + //FT0 = [f(FT0),f(255*FT0), f((255^2)*FT0), f((255^3)*FT0)] where f(number) = number - floor(number)
"mul ft1 ft0.yzww fc2 \n" + //FT1 = [(f(255*FT0))/255.0, (f((255^2)*FT0))/255.0, (f((255^3)*FT0))/255.0, 0.0]
"sub ft0 ft0 ft1 \n" + //FT0 = [f(FT0) - ((f(255*FT0))/255.0), f(255*FT0) - ((f((255^2)*FT0))/255.0), f((255^2)*FT0) - ((f((255^3)*FT0))/255.0), f((255^3)*FT0)]
"mov oc ft0 \n"
)