54 lines
1.4 KiB
Text
54 lines
1.4 KiB
Text
shader_type canvas_item;
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render_mode unshaded;
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// uniforms
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uniform sampler2D screen_texture : hint_screen_texture, repeat_disable, filter_linear_mipmap;
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// constants
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const vec3 BLACK = vec3(0);
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const float glow_strength = 0.5;
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const float glow_size_lod = 3.0;
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const int outline_radius = 1;
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// simple edge detection based on black
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bool is_edge(int radius, vec2 screen_uv, vec2 screen_pixel_size) {
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bool ed_found_bg = false;
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bool ed_found_color = false;
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// check neighbor pixels
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for (int x = -radius; x <= radius; x++) {
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for (int y = -radius; y <= radius; y++) {
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vec4 p = texture(screen_texture, screen_uv + (vec2(float(x), float(y)) * screen_pixel_size));
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if (p.rgb == BLACK) {
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ed_found_bg = true;
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} else {
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ed_found_color = true;
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}
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}
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}
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return ed_found_bg && ed_found_color;
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}
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//
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void fragment() {
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// get screen texture
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vec4 screen = texture(screen_texture, SCREEN_UV);
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// apply edge detection
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if (is_edge(outline_radius, SCREEN_UV, SCREEN_PIXEL_SIZE)) {
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if (screen.rgb != BLACK) { // would be incompatible with target backgrounds != black
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COLOR = screen;
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}
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}
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// apply glow
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// blur a relative radius -> x * log(1.0/SCREEN_PIXEL_SIZE.y)
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// using log, because the LOD value seems to affect the blur radius exponentially
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vec4 glow = textureLod(screen_texture, SCREEN_UV, glow_size_lod);
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if (screen.rgb == BLACK) {
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COLOR += glow * glow_strength;
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}
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// set alpha to 1
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COLOR.a = 1.0;
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}
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