// LS/PT: zShader
//
// Simply maps the Y coordinate to a gray-scale color.
// 1 meter is fully bright, and 0 is dark. Outside
// that range is clamped.
//
// Why is it called "zShader" then? It's a misnomer!
//
// poly@omino.com david van brink 2007
//

@version 2.0

flags
{
    return(COLOR); // we will modify the color of the texture
}

process: sa
// 'sa' is an instance of a Shader Object.
{
    maxHeight = 1.0;
    g = sa.wPos[2] / maxHeight; // y coordinate, 1 = white, 0m = black
    if(g < 0.0)
        g = 0;
    if(g > 1.0)
        g = 1.0;
    
    sa.color[1] = g;
    sa.color[2] = g;
    sa.color[3] = g;

    sa.luminous = 1.0;
    sa.diffuse = 0;
    sa.specular = 0;
    sa.mirror = 0;
    sa.transparency = 0;
}

// eof