godot-demo-projects/3d/sprites/shaders/paper_rainbow.gdshader

shader_type spatial;
render_mode depth_draw_opaque, cull_disabled, depth_prepass_alpha;

uniform sampler2D texture_albedo : source_color, filter_nearest;
uniform sampler2D normal_map : hint_normal;
uniform float outline_thickness : hint_range(0.001, 0.05) = 0.1;
uniform vec4 outline_color : source_color = vec4(1.0, 1.0, 1.0, 1.0);

void fragment() {
	vec2 uv = UV;
	vec4 center = texture(texture_albedo, uv);

	float threshold = 0.1;
	float outline = 0.0;

	vec2 offset = vec2(outline_thickness, 0.0);

	outline += step(threshold, texture(texture_albedo, uv + offset).a);
	outline += step(threshold, texture(texture_albedo, uv - offset).a);
	outline += step(threshold, texture(texture_albedo, uv + vec2(0.0, outline_thickness)).a);
	outline += step(threshold, texture(texture_albedo, uv - vec2(0.0, outline_thickness)).a);

	if (center.a < threshold && outline > 0.0) {
		float t = TIME * 2.0 + uv.x * 10.0 + uv.y * 10.0;
		vec3 rainbow = vec3(
				0.5 + 0.5 * sin(t),
				0.5 + 0.5 * sin(t + 2.0),
				0.5 + 0.5 * sin(t + 4.0));
		ALBEDO = rainbow;
		ALPHA = 1.0;
	} else {
		ALBEDO = center.rgb;
		ALPHA = center.a;
		vec3 normal_tex = texture(normal_map, UV).rgb;
		normal_tex = normal_tex * 2.0 - 1.0;
		NORMAL = normalize(TANGENT * normal_tex.x + BINORMAL * normal_tex.y + NORMAL * normal_tex.z);
	}
}