PS1 Post-processing

This shader is meant to be used with the PS1 Shader. It gives your game that PS1 dithered look. Works in editor, too!

Usage:
Make a MeshInstance, give it a QuadMesh, make the size 2 by 2, set the Extra Cull Margin to the highest possible value, apply a material with this shader to it.

Known issues:
Doesn’t support transparent objects.

Uniforms:
Color Depth – Reduce color depth to X bits per color. The PS1 supported many modes, some of them being 24 bit (8 bits per color) and 15 bit (5 bits per color), the latter (5 bits per color) used in majority of 3D games and being the default.
Dithering – Apply the “dotted” look that gives an illusion of more colors.
Resolution Scale – Reduce screen resolution.

Shader code

shader_type spatial;
render_mode unshaded, shadows_disabled, depth_test_disable, depth_draw_never;

uniform int color_depth : hint_range(1, 8) = 5;
uniform bool dithering = true;
uniform int resolution_scale = 4;

int dithering_pattern(ivec2 fragcoord) {
	const int pattern[] = {
		-4, +0, -3, +1, 
		+2, -2, +3, -1, 
		-3, +1, -4, +0, 
		+3, -1, +2, -2
	};
	
	int x = fragcoord.x % 4;
	int y = fragcoord.y % 4;
	
	return pattern[y * 4 + x];
}

void vertex() {
	POSITION = vec4(VERTEX, 1.0);
}

void fragment() {
	ivec2 uv = ivec2(FRAGCOORD.xy / float(resolution_scale));
	vec3 color = texelFetch(SCREEN_TEXTURE, uv * resolution_scale, 0).rgb;
	
	// Convert from [0.0, 1.0] range to [0, 255] range
	ivec3 c = ivec3(round(color * 255.0));
	
	// Apply the dithering pattern
	if (dithering) {
		c += ivec3(dithering_pattern(uv));
	}
	
	// Truncate from 8 bits to color_depth bits
	c >>= (8 - color_depth);

	// Convert back to [0.0, 1.0] range
	ALBEDO = vec3(c) / float(1 << color_depth);
}

Tags