3D Pixel art outline & highlight Shader (Post-processing/object)

Demo: https://github.com/leopeltola/Godot-3d-pixelart-demo

A shader that adds outlines and highlights to low-res 3D pixel art. Made for Godot 4.

This shader works as both a post-processing and standard material shader.

 

Shader code
shader_type spatial;
render_mode unshaded;

// MIT License. Made by Leo Peltola
// Inspired by https://threejs.org/examples/webgl_postprocessing_pixel.html

uniform sampler2D DEPTH_TEXTURE : hint_depth_texture, filter_linear_mipmap;
uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap;
uniform sampler2D NORMAL_TEXTURE : hint_normal_roughness_texture, filter_nearest;

uniform bool shadows_enabled = true;
uniform bool highlights_enabled = true;
uniform float shadow_strength : hint_range(0.0, 1.0, 0.01) = 0.4;
uniform float highlight_strength : hint_range(0.0, 1.0, 0.01) = 0.1;
uniform vec3 highlight_color : source_color = vec3(1.);
uniform vec3 shadow_color : source_color = vec3(0.0);

varying mat4 model_view_matrix;


float getDepth(vec2 screen_uv, sampler2D depth_texture, mat4 inv_projection_matrix){
//	Credit: https://godotshaders.com/shader/depth-modulated-pixel-outline-in-screen-space/
	float raw_depth = texture(depth_texture, screen_uv)[0];
	vec3 normalized_device_coordinates = vec3(screen_uv * 2.0 - 1.0, raw_depth);
    vec4 view_space = inv_projection_matrix * vec4(normalized_device_coordinates, 1.0);	
	view_space.xyz /= view_space.w;	
	return -view_space.z;
}

vec3 getPos(float depth, mat4 mvm, mat4 ipm, vec2 suv, mat4 wm, mat4 icm){
  vec4 pos = inverse(mvm) * ipm * vec4((suv * 2.0 - 1.0), depth * 2.0 - 1.0, 1.0);
  pos.xyz /= (pos.w+0.0001*(1.-abs(sign(pos.w))));
  return (pos*icm).xyz+wm[3].xyz;
}

float normalIndicator(vec3 normalEdgeBias, vec3 baseNormal, vec3 newNormal, float depth_diff){
	// Credit: https://threejs.org/examples/webgl_postprocessing_pixel.html
	float normalDiff = dot(baseNormal - newNormal, normalEdgeBias);
	float normalIndicator = clamp(smoothstep(-.01, .01, normalDiff), 0.0, 1.0);
	float depthIndicator = clamp(sign(depth_diff * .25 + .0025), 0.0, 1.0);
	return (1.0 - dot(baseNormal, newNormal)) * depthIndicator * normalIndicator;
}

void vertex(){
    model_view_matrix = VIEW_MATRIX * mat4(INV_VIEW_MATRIX[0], INV_VIEW_MATRIX[1], INV_VIEW_MATRIX[2], MODEL_MATRIX[3]);
}

void fragment() {
	vec2 e = vec2(1./VIEWPORT_SIZE.xy);
	
//	Shadows
	float depth_diff = 0.0;
	float neg_depth_diff = .5;
	if (shadows_enabled) {
		float depth = getDepth(SCREEN_UV, DEPTH_TEXTURE, INV_PROJECTION_MATRIX);
		float du = getDepth(SCREEN_UV+vec2(0., -1.)*e, DEPTH_TEXTURE, INV_PROJECTION_MATRIX);
		float dr = getDepth(SCREEN_UV+vec2(1., 0.)*e, DEPTH_TEXTURE, INV_PROJECTION_MATRIX);
		float dd = getDepth(SCREEN_UV+vec2(0., 1.)*e, DEPTH_TEXTURE, INV_PROJECTION_MATRIX);
		float dl = getDepth(SCREEN_UV+vec2(-1., 0.)*e, DEPTH_TEXTURE, INV_PROJECTION_MATRIX);
		depth_diff += clamp(du - depth, 0., 1.);
		depth_diff += clamp(dd - depth, 0., 1.);
		depth_diff += clamp(dr - depth, 0., 1.);
		depth_diff += clamp(dl - depth, 0., 1.);
		neg_depth_diff += depth - du;
		neg_depth_diff += depth - dd;
		neg_depth_diff += depth - dr;
		neg_depth_diff += depth - dl;
		neg_depth_diff = clamp(neg_depth_diff, 0., 1.);
		neg_depth_diff = clamp(smoothstep(0.5, 0.5, neg_depth_diff)*10., 0., 1.);
		depth_diff = smoothstep(0.2, 0.3, depth_diff);
//		ALBEDO = vec3(neg_depth_diff);
	}
	
//	Highlights
	float normal_diff = 0.;
	if (highlights_enabled) {
		vec3 normal = texture(NORMAL_TEXTURE, SCREEN_UV).rgb * 2.0 - 1.0;
		vec3 nu = texture(NORMAL_TEXTURE, SCREEN_UV+vec2(0., -1.)*e).rgb * 2.0 - 1.0;
		vec3 nr = texture(NORMAL_TEXTURE, SCREEN_UV+vec2(1., 0.)*e).rgb * 2.0 - 1.0;
		vec3 nd = texture(NORMAL_TEXTURE, SCREEN_UV+vec2(0., 1.)*e).rgb * 2.0 - 1.0;
		vec3 nl = texture(NORMAL_TEXTURE, SCREEN_UV+vec2(-1., 0.)*e).rgb * 2.0 - 1.0;
		vec3 normal_edge_bias = (vec3(1., 1., 1.));
		normal_diff += normalIndicator(normal_edge_bias, normal, nu, depth_diff);
		normal_diff += normalIndicator(normal_edge_bias, normal, nr, depth_diff);
		normal_diff += normalIndicator(normal_edge_bias, normal, nd, depth_diff);
		normal_diff += normalIndicator(normal_edge_bias, normal, nl, depth_diff);
		normal_diff = smoothstep(0.2, 0.8, normal_diff);
		normal_diff = clamp(normal_diff-neg_depth_diff, 0., 1.);
//		ALBEDO = vec3(normal_diff);
	}
	

	vec3 original_color = texture(SCREEN_TEXTURE, SCREEN_UV).rgb;
	vec3 final_highlight_color = mix(original_color, highlight_color, highlight_strength);
	vec3 final_shadow_color = mix(original_color, shadow_color, shadow_strength);
	vec3 final = original_color;
	if (highlights_enabled) {
		final = mix(final, final_highlight_color, normal_diff);
	}
	if (shadows_enabled) {
		final = mix(final, final_shadow_color, depth_diff);
	}
	ALBEDO = final;

	float alpha_mask = depth_diff * float(shadows_enabled) + normal_diff * float(highlights_enabled);
	ALPHA = clamp((alpha_mask) * 5., 0., 1.);
}
Tags
3D pixelart, highlight, outline, pixelart
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.

More from leopeltola

3D Pixel art outline/highlight Shader (Old)

Related shaders

3D Pixel art outline/highlight Shader (Old)

PS1 Post-processing

Stylized shadows, not a post processing

guest

4 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments
QuibblingComet
QuibblingComet
2 months ago

Just wondering how this is applied to the screen? On the godot site they say for post processing effects to use a meshinstance with a quad mesh, I tried this but to no avail. What steps do you take? Thanks!

QuibblingComet
QuibblingComet
2 months ago
Reply to  leopeltola

I got the shader working, and it looks great! I have a couple questions if you don’t mind:

1.
In regards to the normal edges not being drawn between the object and the floor, is that intentional? I noticed your previous iteration did this. I guess it could be tweaked?

2.
Have you found a way in godot to reduce the amount of aliasing produced by having so many edges drawn? It seems fine when you aren’t moving the camera, but otherwise it gets a bit messy :/

And final comment I would like to thank you for the work you’ve done. It’s much appreciated.