feat(default): faster rand in default project

default/inc_rand.glsl

@@ -1,14 +1,20 @@
 #ifndef INC_RAND
 #define INC_RAND
 
+// https://thebookofshaders.com/10/
+// https://byteblacksmith.com/improvements-to-the-canonical-one-liner-glsl-rand-for-opengl-es-2-0/
+
 float rand(float seed){
-    float v = pow(abs(seed), .8571429); // 6. / 7.
-    v *= sin(v) + 1.;
-    return fract(v);
+    const float c =  43758.5453;
+    return fract(sin(seed) * c);
 }
 
-float rand(vec2 n){
-    return rand(n.x * 1234. + n.y * 9876.);
+float rand(vec2 co)
+{
+    const float a = 12.9898;
+    const float b = 78.233;
+    float dt= dot(co.xy ,vec2(a,b));
+    return rand(dt);
 }
 
 #endif