Texture Mapping

Channel Selection
Using the renderman shading language the red channel of a texture map was selected and made transparent.

Texture Map

Render

Select the red channel:
red = comp(surfcolor,0)
Subtract the red values from the opacity:
Oi = color(1-red,green,blue);

Composited Image in Photoshop

(Background painting by Dutch artist Pieter Claesz, 1624.)

Maya Scene

Shader Settings in Maya

This set of sliders in Slim be used to effect the redness, blueness and greenness of a texture map, as well as, move the texture in the s and t direction.

Code

/* basic texture mapper */
surface
texture_mapper(	float	Kd = 1,
				s_offset = .3,
	/*Offset of texture in s direction*/
				t_offset = .3,
	/*Offset of texture in t direction*/
				redness = 1,	
/*amount of redness in texture*/
				greenness = 1,
	/*amount of greenness in texture*/
				blueness = 1,	
/*amount of blueness in texture*/
				switch = 0;		
/*turning red transparency on or off*/
				string	texname = "")
	/*texture to apply to object*/
				
{

color	surfcolor = color(1, 1, 1);
normal	n = normalize(N);
normal	nf = faceforward(n, I);
Oi = Os;


/*	Use the texture function if user spe
cifies a texture file*/
if(texname != "") {
	surfcolor = texture(texname, s +
 s_offset, t + t_offset);

	/*pull the colors out*/
	float red = comp(surfcolor,0);
	float green = comp(surfcolor,1);
	float blue = comp(surfcolor,2);

	surfcolor = color(red*redness,green
*greenness,blue*blueness);

	/*Make the red values transparent*/
	Oi = color(1-red,green,blue);
}


color	diffusecolor = Kd * diffuse(nf);


Ci = Oi * Cs * surfcolor * diffusecolor;