// vert //

void main(void) {
	qgl_FragTexture = qgl_Texture;
	gl_Position = qgl_ftransform();
}


// frag //

uniform vec2 dt, size;
uniform float thickness;

void main(void) {
	vec2 frame_size = size / dt;
	vec2 pix_pos = qgl_FragTexture * frame_size;
	vec2 frame = vec2(1) + step(pix_pos, vec2(thickness)) - step(pix_pos, frame_size - vec2(thickness));
	vec2 line = frame * step(0.5, fract(pix_pos.yx / thickness / 4.));
	float fc = max(frame.x, frame.y);
	float fl = max(line.x , line.y );
	fl = mix(1, fl, fc);
	qgl_FragColor = vec4(vec3(fl), fc * 0.8 + 0.2);
	//qgl_FragColor = vec4(vec3(fl,0),1);
}