Writing mental ray shaders: Color Offset

Goal

A simple shader that takes a base color and adds another color.

Methodology

1. create a color parameter called base

2. create a color parameter called offset

3. create a shader called "color_offset"

4. create a function where result = base + offset

Mi File

declare shader
 color "color_offset" (
  color "base"  default 1 1 1,
  color "offset" default 0 0 0
 )
 apply material
end declare

C File

#include "shader.h"

DLLEXPORT

struct color_offset {
 miColor base;
 miColor offset;
};

DLLEXPORT

miBoolean color_offset (miColor *result, miState *state, struct color_offset *params) {
 miColor *base = mi_eval_color(&params->base);
 miColor *offset = mi_eval_color(&params->offset);
 result->r = base->r + offset->r;
 result->g = base->g + offset->g;
 result->b = base->b + offset->b;
 return miTRUE;
 }