initial: added basic stuff

README.md

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+# GLSL playground
+
+A few sketches I made while working throught [The Book of Shaders](https://thebookofshaders.com/).

basic/colorchange.glsl

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+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform float u_time;
+
+void main() {
+	gl_FragColor = vec4(abs(sin(u_time)),0.5,abs(tan(u_time*0.5)),1.0);
+}

basic/colorchange_mouse.glsl

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+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_time;
+
+void main() {
+	vec2 st = (gl_FragCoord.xy+u_mouse)/(u_resolution*vec2(2, 2));
+	gl_FragColor = vec4(st.x, st.y, abs(sin(u_time)*0.8), 1.0);
+}

basic/dancing_funs.glsl

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+#ifdef GL_ES
+precision mediump float;
+#endif
+
+#define PI 3.14159265359
+
+uniform vec2 u_resolution;
+uniform float u_time;
+
+float plot (vec2 st, float pct){
+  return  smoothstep( pct-0.01, pct, st.y) -
+          smoothstep( pct, pct+0.01, st.y);
+}
+
+void main() {
+    vec2 st = gl_FragCoord.xy/u_resolution.xy;
+    vec3 color = vec3(0.0);
+
+    vec3 pct = vec3(st.x);
+
+     pct.r = smoothstep(0.0,1.0, st.x*abs(sin(u_time)));
+     pct.g = sin(st.x*PI*u_time);
+     pct.b = pow(st.x*abs(cos(u_time)),0.5);
+
+    // Plot transition lines for each channel
+    color = mix(vec3(0.0),vec3(1.0,0.0,0.0),plot(st,pct.r));
+    color = mix(color,vec3(0.0,1.0,0.0),plot(st,pct.g));
+    color = mix(color,vec3(0.0,0.0,1.0),plot(st,pct.b));
+
+    gl_FragColor = vec4(color,1.0);
+}

basic/dancing_sine.glsl

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+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform vec2 u_resolution;
+uniform float u_time;
+
+float plot(vec2 st, float pct){
+  return  smoothstep( pct-0.02, pct, st.y) - 
+          smoothstep( pct, pct+0.02, st.y);
+}
+
+void main() {
+    vec2 st = gl_FragCoord.xy/u_resolution;
+
+    float y = sin(st.x*u_time);
+
+    float pct = plot(st,y);
+    vec3 color = pct*vec3(0.0,1.0,0.0);
+
+    gl_FragColor = vec4(color,1.0);
+}

basic/sunset.glsl

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+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform vec2 u_resolution;
+uniform float u_time;
+
+void main() {
+    vec2 st = gl_FragCoord.xy/u_resolution.xy;
+    vec3 sun = vec3(1.0*abs(sin(u_time)), .0, 0.4*abs(cos(u_time)));
+
+    vec3 pct = vec3(st.x);
+
+    vec3 color = sun;
+    color *= vec3(step(0.4, st.y));
+    if (step(0.4, st.y)<1.0) {
+    	color = sun * vec3(smoothstep(0.2, 0.4, st.y));
+    	color += vec3(0.3,0.2,0.9);
+    }
+    gl_FragColor = vec4(color,1.0);
+}