Add frame buffers

frontend/src/shaders/cave-distance-fs.glsl

@@ -0,0 +1,39 @@
+#version 300 es
+
+precision mediump float;
+
+
+#define INFINITY 10000.0
+#define LINE_COUNT 50
+
+
+uniform vec2[LINE_COUNT * 2] lines;
+uniform float[LINE_COUNT] radii;
+
+float lineDistance(in vec2 target, in vec2 start, in vec2 end, in float radius) {
+    vec2 pa = target - start, ba = end - start;
+    float h = clamp(dot(pa, ba) / dot(ba, ba), 0.0, 1.0);
+    return distance(pa, ba * h) - radius;
+}
+
+float getDistance(in vec2 target) {
+    float minDistance = INFINITY;
+
+    for (int i = 0; i < LINE_COUNT; i++) {
+        vec2 start = lines[2 * i];
+        vec2 end = lines[2 * i + 1];
+        float r = radii[i];
+        minDistance = min(minDistance, lineDistance(target, start, end, r));
+    }
+
+    return -minDistance;
+}
+
+uniform mat3 transform;
+out vec4 fragmentColor;
+
+void main() {
+    vec2 position = (vec3(gl_FragCoord.xy, 1.0) * transform).xy;
+    float distance = getDistance(position);
+    fragmentColor = vec4(vec3(0.0), distance / 256.0 + 0.5);
+}