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@dannygarcia
Created June 28, 2017 16:27
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Draws a square in a fragment shader (unoptimized implementation).
#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_resolution.xy;
vec3 color = vec3(0.0);
float left = 1.0 - step(0.1,st.x) + step(0.2,st.x) + step(0.9,st.y) + 1.0-step(0.1,st.y);
float bottom = 1.0 - step(0.1,st.y) + step(0.2,st.y) + step(0.9,st.x) + 1.0-step(0.1,st.x);
float right = 1.0 - step(0.8,st.x) + step(0.9,st.x) + step(0.9,st.y) + 1.0-step(0.1,st.y);
float top = 1.0 - step(0.8,st.y) + step(0.9,st.y) + step(0.9,st.x) + 1.0-step(0.1,st.x);
float pct = left * bottom * right * top;
color = vec3(pct);
gl_FragColor = vec4(color,1.0);
}
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