Eevee: Optimize Color Ramp node for common cases.

source/blender/gpu/shaders/gpu_shader_material.glsl

@@ -802,6 +802,19 @@ void mix_linear(float fac, vec4 col1, vec4 col2, out vec4 outcol)
 	outcol = col1 + fac * (2.0 * (col2 - vec4(0.5)));
 }
 
+void valtorgb_opti_constant(float fac, float edge, vec4 color1, vec4 color2, out vec4 outcol, out float outalpha)
+{
+	outcol = (fac > edge) ? color2 : color1;
+	outalpha = outcol.a;
+}
+
+void valtorgb_opti_linear(float fac, vec2 mulbias, vec4 color1, vec4 color2, out vec4 outcol, out float outalpha)
+{
+	fac = clamp(fac * mulbias.x + mulbias.y, 0.0, 1.0);
+	outcol = mix(color1, color2, fac);
+	outalpha = outcol.a;
+}
+
 void valtorgb(float fac, sampler1DArray colormap, float layer, out vec4 outcol, out float outalpha)
 {
 	outcol = texture(colormap, vec2(fac, layer));