GLSL Triangle function

triangle.frag

// via "Einstienstien" - by Dave Hoskins, on Shadertoy
// http://glsl.heroku.com/e#10662.0

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 resolution;

float col = 0.0; // Start black.
vec2 uv;

void Tri(vec4 p)
{
	vec4 unC1 = (floor(mod(p, 256.0)) / vec4(395.,395.,395.,256.));
	vec4 unC2 = (floor(p / 256.0)) / vec4(256.0);
	vec2 a = vec2(unC1.x+.18, unC2.x);
	vec2 b = vec2(unC1.y+.18, unC2.y);
	vec2 c = vec2(unC1.z+.18, unC2.z);
    	vec2 as = uv-a;
	bool uv_ab = (b.x-a.x)*as.y-(b.y-a.y)*as.x > 0.0;
    	if ((c.x-a.x)*as.y-(c.y-a.y)*as.x > 0.0 == uv_ab) return;
    	if ((c.x-b.x)*(uv.y-b.y)-(c.y-b.y)*(uv.x-b.x) > 0.0 != uv_ab) return;
	col = mix (col, unC1.w, unC2.w); 
}

void main(void)
{
	uv = gl_FragCoord.xy / resolution.xy;

	Tri(vec4(30702., 34338.,40328., 14851.));

	gl_FragColor = vec4(vec3(col), 1.0 );
}