shaders

commit d608712bb19f4732d4b835a9c6623562c54b1d2a
parent e0e2a8ba8fac3fd35ed446a0db17d439c8fa050d
Author: mpizzzle <m@michaelpercival.xyz>
Date:   Mon,  7 Sep 2020 17:07:33 +0100

added function to draw a quadratic through given point (mouse coordinates)

Diffstat:
A
curve-through-point.frag
 | 
33
+++++++++++++++++++++++++++++++++

1 file changed, 33 insertions(+), 0 deletions(-)
diff --git a/curve-through-point.frag b/curve-through-point.frag
@@ -0,0 +1,33 @@
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+#define PI 3.14159265359
+
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_time;
+
+float quadraticThroughPoint(float x, vec2 ab) {
+    float epsilon = 0.00001;
+    float a = min(1.0 - epsilon, max(0.0 + epsilon, ab.x));  
+    float b = min(1.0, max(0.0, ab.y)); 
+    float A = (1.0 - b) / (1.0 - a) - (b / a);
+    float B = (A * (a * a) - b) / a;
+    float y = A * (x * x) - B * (x);
+    return min(1.0, max(0.0, y)); 
+}
+
+void main() {
+    vec2 st = gl_FragCoord.xy / u_resolution;
+
+    float y = quadraticThroughPoint(st.x, u_mouse / u_resolution);
+    vec3 color = vec3(y);
+
+    float plot = smoothstep(y - 0.02, y, st.y) - smoothstep(y, y + 0.02, st.y);
+
+    color = (1.0 - plot) * color + plot * vec3(1.0, 0.0, 1.0);
+
+    gl_FragColor = vec4(color, 1.0);
+}
+