quakeforge/libs/video/renderer/glsl/quakespr.frag

uniform sampler2D spritea;
uniform sampler2D spriteb;
uniform sampler2D palette;
varying float blend;
varying vec4 colora, colorb;
varying vec2 sta, stb;

void
main (void)
{
	float       pixa, pixb;
	vec4        cola, colb;
	vec4        col;

	pixa = texture2D (spritea, sta).r;
	pixb = texture2D (spriteb, stb).r;
	if (pixa == 1.0 && pixb == 1.0)
		discard;
	cola = texture2D (palette, vec2 (pixa, 0.0)) * colora;
	colb = texture2D (palette, vec2 (pixb, 0.0)) * colorb;
	col = mix (cola, colb, blend);
	if (col.a == 0.0)
		discard;
	gl_FragColor = col;
}