+4

Retro dither

A dithering shader for rendering retro polygonal meshes.

This is GLES2 which does not have loops, arrays or array access. In GLES3 this would be a lot shorter and simpler.

Also this does not handle alpha yet.

Shader code
shader_type spatial;
render_mode blend_mix, depth_draw_opaque, cull_back, diffuse_burley;

uniform vec4 color: hint_color = vec4(0.5, 0.4, 0.4, 1.0);
uniform float shade_tweak: float = 0.5;
uniform float light_tweak: float = 1.0;
uniform float sharpness: float = 1.0;
uniform float scale: float = 2.0;

const mat4 dither = mat4(
	vec4(0.0, 0.5333333333, 0.1333333333,  0.6666666667),
	vec4(0.8, 0.2666666667, 0.9333333333,  0.4),
	vec4(0.2, 0.7333333333, 0.06666666667, 0.6),
	vec4(1.0, 0.4666666667, 0.8666666667,  0.3333333333)
);

void fragment() {
	ALBEDO = COLOR.rgb * color.rgb;
}

float sample(vec2 coord, float alpha, float shade, float lit) {
	int x = int(mod(coord.x, 4));
	int y = int(mod(coord.y, 4));
	if (y == 0) {
		if (x == 0 && dither[0][0] >= alpha) {
			return shade;
		} else if (x == 1 && dither[0][1] >= alpha) {
			return shade;
		} else if (x == 2 && dither[0][2] >= alpha) {
			return shade;
		} else if (x == 3 && dither[0][3] >= alpha) {
			return shade;
		}
	} else if (y == 1) {
		if (x == 0 && dither[1][0] >= alpha) {
			return shade;
		} else if (x == 1 && dither[1][1] >= alpha) {
			return shade;
		} else if (x == 2 && dither[1][2] >= alpha) {
			return shade;
		} else if (x == 3 && dither[1][3] >= alpha) {
			return shade;
		}
	} else if (y == 2) {
		if (x == 0 && dither[2][0] >= alpha) {
			return shade;
		} else if (x == 1 && dither[2][1] >= alpha) {
			return shade;
		} else if (x == 2 && dither[2][2] >= alpha) {
			return shade;
		} else if (x == 3 && dither[2][3] >= alpha) {
			return shade;
		}
	} else if (y == 3) {
		if (x == 0 && dither[3][0] >= alpha) {
			return shade;
		} else if (x == 1 && dither[3][1] >= alpha) {
			return shade;
		} else if (x == 2 && dither[3][2] >= alpha) {
			return shade;
		} else if (x == 3 && dither[3][3] >= alpha) {
			return shade;
		}
	}
	return lit;
}

void light() {
	float f = min(ATTENUATION.r, min(ATTENUATION.g, ATTENUATION.b));
	float a = sample(
		FRAGCOORD.xy * (1.0 / scale),
		clamp(dot(NORMAL, LIGHT) + sharpness, 0.0, 1.0 + sharpness) * f,
		shade_tweak,
		light_tweak);
	DIFFUSE_LIGHT += ALBEDO * a;
}
Tags
dithering, retro
The shader code and all code snippets in this post are under CC0 license and can be used freely without the author's permission. Images and videos, and assets depicted in those, do not fall under this license. For more info, see our License terms.

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paddy-exe
paddy-exe
1 month ago

Looks awesome! Would love to see a GLES3 shader as well 😀