init

ghostty-shaders/just-snow.glsl

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+// Copyright (c) 2013 Andrew Baldwin (twitter: baldand, www: http://thndl.com)
+// License = Attribution-NonCommercial-ShareAlike (http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_US)
+
+// "Just snow"
+// Simple (but not cheap) snow made from multiple parallax layers with randomly positioned 
+// flakes and directions. Also includes a DoF effect. Pan around with mouse.
+
+#define LIGHT_SNOW // Comment this out for a blizzard
+
+#ifdef LIGHT_SNOW
+	#define LAYERS 50
+	#define DEPTH .5
+	#define WIDTH .3
+	#define SPEED .6
+#else // BLIZZARD
+	#define LAYERS 200
+	#define DEPTH .1
+	#define WIDTH .8
+	#define SPEED 1.5
+#endif
+
+void mainImage( out vec4 fragColor, in vec2 fragCoord )
+{
+	const mat3 p = mat3(13.323122,23.5112,21.71123,21.1212,28.7312,11.9312,21.8112,14.7212,61.3934);
+	vec2 uv = fragCoord.xy / iResolution.xy;
+
+	vec3 acc = vec3(0.0);
+	float dof = 5.0 * sin(iTime * 0.1);
+	for (int i = 0; i < LAYERS; i++) {
+		float fi = float(i);
+		vec2 q =-uv*(1.0 + fi * DEPTH);
+		q += vec2(q.y * (WIDTH * mod(fi * 7.238917, 1.0) - WIDTH * 0.5), -SPEED * iTime / (1.0 + fi * DEPTH * 0.03));
+		vec3 n = vec3(floor(q), 31.189 + fi);
+		vec3 m = floor(n) * 0.00001 + fract(n);
+		vec3 mp = (31415.9 + m) / fract(p * m);
+		vec3 r = fract(mp);
+		vec2 s = abs(mod(q, 1.0) - 0.5 + 0.9 * r.xy - 0.45);
+		s += 0.01 * abs(2.0 * fract(10.0 * q.yx) - 1.0); 
+		float d = 0.6 * max(s.x - s.y, s.x + s.y) + max(s.x, s.y) - 0.01;
+		float edge = 0.005 + 0.05 * min(0.5 * abs(fi - 5.0 - dof), 1.0);
+		acc += vec3(smoothstep(edge, -edge, d) * (r.x / (1.0 + 0.02 * fi * DEPTH)));
+	}
+	
+	// Sample the terminal screen texture including alpha channel
+	vec4 terminalColor = texture(iChannel0, uv);
+
+	// Combine the snow effect with the terminal color
+	vec3 blendedColor = terminalColor.rgb + acc;
+
+	// Use the terminal's original alpha
+	fragColor = vec4(blendedColor, terminalColor.a);
+}