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September 23, 2016 21:35
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Cleaner implementation of the Spiral fragment shader
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| // Author: Akshay S. Loke | |
| // Title: Spiral | |
| #ifdef GL_ES | |
| precision mediump float; | |
| #endif | |
| #define USE_SMOOTH | |
| #define M_PI 3.14159265358979 | |
| #define M_2PI 6.28318530717958 | |
| #define RADIUS 0.2 | |
| #define NUMCURLS 3 | |
| uniform vec2 u_resolution; | |
| uniform vec2 u_mouse; | |
| uniform float u_time; | |
| void main() { | |
| vec2 center = u_resolution * 0.5; | |
| vec2 normCenter = vec2(0.0); | |
| vec2 uv = gl_FragCoord.xy; | |
| vec2 normUV = gl_FragCoord.xy / u_resolution.xy; | |
| normUV = normUV * 2.0 - vec2(1.0); | |
| float dist = length(normUV - normCenter); | |
| float theta = atan(normUV.y, normUV.x) + M_PI; | |
| float normTheta = theta / M_2PI; | |
| /*float val0 = step(0.0, dist) - step(normTheta * RADIUS, dist); | |
| float val1 = step(normTheta * RADIUS, dist) - step((normTheta + 1.0) * RADIUS, dist); | |
| float val = (val0 * normTheta + val1 * (normTheta + 1.0)) * 0.5; | |
| float smoothVal0 = smoothstep(0.0, 0.0, dist) - smoothstep(normTheta * RADIUS - 0.01, normTheta * RADIUS, dist); | |
| float smoothVal1 = smoothstep(normTheta * RADIUS - 0.01, normTheta * RADIUS, dist) - smoothstep((normTheta + 1.0) * RADIUS - 0.01, (normTheta + 1.0) * RADIUS, dist); | |
| float smoothVal = (smoothVal0 * normTheta + smoothVal1 * (normTheta + 1.0)) * 0.5; | |
| */ | |
| float val = 0.0; | |
| float numCurlsFloat = float(NUMCURLS); | |
| for (int i=-1; i<NUMCURLS-1; i++) { | |
| float index = float(i); | |
| float normThetaPre = (normTheta + index); | |
| float ringPre = normThetaPre * RADIUS; | |
| if (i == -1) { | |
| ringPre = 0.0; | |
| } | |
| float normThetaPost = (normTheta + index + 1.0); | |
| float ringPost = normThetaPost * RADIUS; | |
| #ifdef USE_SMOOTH | |
| float ringVal = smoothstep(ringPre-0.01, ringPre, dist) - smoothstep(ringPost-0.01, ringPost, dist); | |
| #else | |
| float ringVal = step(ringPre, dist) - step(ringPost, dist); | |
| #endif | |
| val += (ringVal * normThetaPost); | |
| } | |
| val /= numCurlsFloat; | |
| gl_FragColor = vec4(vec3(val), 1.0); | |
| } |
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