Shaping_I_(Square).frag

// Author: Jeremy Rotsztain 
// Workshop: Generating Images with Shaders @ InterAccess, 2020
// Title: Shaping I: Square

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

void main() {
    
    // get the xy coordinates & normalize to [0, 1] range
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st.x *= u_resolution.x/u_resolution.y;

    // setup an rgb fill color 
    vec3 color = vec3(0.);

    // square fills 60% of canvas (20% border on each side)
    // use step to show pixels that are greater than 0.2
    color.r = step(0.2, st.x);
    
    // use step to show pixels that are less than 0.8
    // note 1.0-vale to invert results
    //color.g = 1.0-step(0.8, st.x);
    //color.r *= 1.0-step(0.8, st.x);

    // make a red square (for malevich)
    // note: disable green channel first!
    //color.r *= step( 0.2, st.y);
    //color.r *= 1.0-step( 0.8, st.y);
    
    gl_FragColor = vec4(color, 1.0);
}