/*
    Hurry Curry! - a game about cooking
    Copyright 2024 metamuffin

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, version 3 of the License only.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.

*/
shader_type spatial;
render_mode unshaded;

uniform sampler2D screen_texture : hint_screen_texture, repeat_enable, filter_nearest;

varying vec3 world_camera;
varying vec3 world_position;

uniform float type : hint_range(-1.0, 1.0);
uniform float size : hint_range(0.0, 2.0);

void vertex() {
	MODELVIEW_MATRIX = VIEW_MATRIX * mat4(
		INV_VIEW_MATRIX[0],
		INV_VIEW_MATRIX[1],
		INV_VIEW_MATRIX[2],
		MODEL_MATRIX[3]
	);
	world_position = VERTEX;
	world_camera = (inverse(MODELVIEW_MATRIX) * vec4(0, 0, 0, 1)).xyz;
}

void fragment() {
	vec3 ray = world_camera / size;
	vec3 rv = normalize(world_position - world_camera);
	vec3 em = vec3(0.);
	bool hit = false;

	for (int i = 0; i < 100; i++) {
		float st = length(ray) * 0.1;
		ray += normalize(rv) * st;
		if (length(ray) < 1.) { hit = true; break; }
		rv += -normalize(ray) * -type / exp(dot(ray,ray)) * st;
		em += st * smoothstep(1.5,1.2,length(ray)) * 0.2;
	}

	vec4 k = PROJECTION_MATRIX * vec4(rv*1000.0, 1.0);
	k /= k.w;
	vec2 k2 = (k.xy + 1.) / 2.;

	vec3 col = hit ? vec3(type*0.5+0.5) : texture(screen_texture, k2).rgb;
	col += vec3(0.3,0.0,1.0) * max(em - 0.1,0.);
	ALBEDO = col;
}