shader_type spatial;
render_mode cull_front, unshaded;

uniform vec4 outline_color : source_color = vec4(0.0, 0.0, 0.0, 1.0);
uniform float thickness : hint_range(0.0, 10.0) = 5.0; // Thickness in pixels

void vertex() {
	// Calculate the vertex position and normal in projection space
	vec4 clip_position = PROJECTION_MATRIX * (MODELVIEW_MATRIX * vec4(VERTEX, 1.0));
	vec3 clip_normal = mat3(PROJECTION_MATRIX) * (mat3(MODELVIEW_MATRIX) * NORMAL);
	
	// Normalize the normal vector and convert to pixel space
	vec2 clip_norm = normalize(clip_normal.xy);
	vec2 pixel_size = 1.0 / VIEWPORT_SIZE;
	
	// Multiply by W to keep pixel size constant across distances
	clip_position.xy += clip_norm * pixel_size * thickness * clip_position.w;
	
	POSITION = clip_position;
}

void fragment() {
	ALBEDO = outline_color.rgb;
}