mirror of
https://github.com/patriciogonzalezvivo/thebookofshaders
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40 lines
1.1 KiB
GLSL
40 lines
1.1 KiB
GLSL
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// By Jaskirat Randhawa ( http://jaskirat.me/ )
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// For Shader Studio Course https://github.com/patriciogonzalezvivo/ss2015
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#ifdef GL_ES
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precision mediump float;
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#endif
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#define PI 3.14159265359
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uniform vec2 u_resolution;
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uniform float u_time;
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void main (void)
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{
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// float fade_out = 1.-abs(sin(u_time)-cos(u_time));
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float fade_out = 1.-mod(u_time, 2.); // SAW TOOTH FUNCTION
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float border = abs(sin(fade_out/3.)); // 0.01
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float circle_radius= 1.-(fade_out); // 0.5
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vec4 circle_color= vec4(1.0, 1.0, 1.0, fade_out);
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vec2 circle_center= vec2(0.5, 0.5);
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vec2 st = gl_FragCoord.xy/u_resolution.xy;
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vec4 bkg_color = vec4(0.);
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// Offset st with the center of the circle.
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st = st - circle_center;
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// float dist = sqrt(dot(st/.2, circle_center*2.)); //????
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// float dist = sqrt(st.x*st.x+st.y*st.y); //r^2 = x^2 + y^2 // Equation of circle
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float dist = sqrt(dot(st/.2, st/.2)); //Equation of circle using dot product
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float t = 1.0 + smoothstep(circle_radius, circle_radius+border, dist)
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- smoothstep(circle_radius-border, circle_radius, dist);
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gl_FragColor = mix(circle_color, bkg_color,t);
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}
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