1 files changed, 54 insertions, 0 deletions
diff --git a/examples/polygon.frag b/examples/polygon.frag
new file mode 100644
index 0000000..20d5cdc
--- /dev/null
+++ b/examples/polygon.frag
@@ -0,0 +1,54 @@
+#version 330
+
+out vec4 fragColor;
+
+uniform vec2 res;
+uniform float time;
+
+const float sharpness = 300;
+
+const float PI = 3.14159265358979323846;
+
+
+mat2 rot(float a) {
+        return mat2(
+                cos(a), -sin(a),
+                sin(a), cos(a)
+        );
+}
+
+float poly(float n, vec2 m, float r, float rt, vec2 p) {
+        vec2 diff = (m - p) * rot(rt);
+        float d = length(diff);
+        float alpha = PI / n;
+        float gamma = mod(abs(atan(diff.x, diff.y)), alpha*2);
+
+        if (gamma > alpha)
+                gamma -= 2*alpha;
+
+        float r2 = r * cos(alpha) / cos(gamma);
+
+        return clamp((r2 - d)*sharpness, 0.0, 1.0);
+}
+
+float poly_d(float n, vec2 m, float r, float rt, vec2 p) {
+        return poly(n, m, r, rt, p) - poly(n, m, r - 1/sharpness, rt, p);
+}
+
+void main(void) {
+        vec2 m = res/2;
+        float s = min(m.x, m.y);
+        vec2 p = (gl_FragCoord.xy - m) / s;
+
+        float scene = 0;
+
+        float c;
+
+        c = poly_d(5 - 3*cos(time/1000), vec2(0, 0), 0.5, PI * time/1000, p);
+        scene = abs(scene - c);
+
+        c = poly_d(5 - 3*cos(time/1000), vec2(0, 0), 0.5, -PI * time/1000, p);
+        scene = abs(scene - c);
+
+        fragColor = vec4(vec3(1, 1, 1) * scene, 1);
+}