GLSL中的形状

部分参考： 《OpenGL 编程指南》、《The Book of Shader》

长方形

// Author @patriciogv - 2015
// http://patriciogonzalezvivo.com

#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);

    // bottom-left
    // step 比0.1大 1  小 0
    vec2 bl = step(vec2(0.1),st);
    //放大边框
    float pct = bl.x * bl.y;

    // top-right
    // vec2 tr = step(vec2(0.1),1.0-st);
    // pct *= tr.x * tr.y;

    color = vec3(pct);

    gl_FragColor = vec4(color,1.0);
}

#ifdef GL_ES
precision mediump float;
# endif
uniform vec2 u_resolution;  
void main() {
    vec2 uv = gl_FragCoord.xy / u_resolution.xy;
    vec4 color = vec4(0.129, 0.588, 0.953, 1.0);
    if (uv.x < 0.6 && uv.y < 0.6) {
        gl_FragColor = color;
    } else {
        gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
        // gl_FragColor = color;
    }
}

圆

// Author @patriciogv - 2015
// http://patriciogonzalezvivo.com

#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;
    float pct = 0.0;

    // a. The DISTANCE from the pixel to the center
    pct = distance(st,vec2(0.5));

    // b. The LENGTH of the vector
    //    from the pixel to the center
    // vec2 toCenter = vec2(0.5)-st;
    // pct = length(toCenter);

    // c. The SQUARE ROOT of the vector
    //    from the pixel to the center
    // vec2 tC = vec2(0.5)-st;
    // pct = sqrt(tC.x*tC.x+tC.y*tC.y);

    vec3 color = vec3(pct);

 gl_FragColor = vec4( color, 1.0 );
}

//作者：https://www.shadertoy.com/view/XdlSDs

# ifdef GL_ES
precision mediump float;
# endif
uniform vec3 iResolution;
uniform float iTime;
uniform vec4 iDate;

void main() {
 vec2 p = (2.0*gl_FragCoord.xy-iResolution.xy)/iResolution.y;
 float tau = 3.1415926535*2.0;
 float a = atan(p.x,p.y);
 float r = length(p)*0.75;
 vec2 uv = vec2(a/tau,r);
 
 //get the color
 float xCol = (uv.x - (iTime / 3.0)) * 3.0;
 xCol = mod(xCol, 3.0);
 vec3 horColour = vec3(0.25, 0.25, 0.25);
 
 if (xCol < 1.0) {
  
  horColour.r += 1.0 - xCol;
  horColour.g += xCol;
 }
 else if (xCol < 2.0) {
  
  xCol -= 1.0;
  horColour.g += 1.0 - xCol;
  horColour.b += xCol;
 }
 else {
  
  xCol -= 2.0;
  horColour.b += 1.0 - xCol;
  horColour.r += xCol;
 }

 // draw color beam
 uv = (2.0 *uv) - 1.0;
 float beamWidth = (0.7+0.5*cos(uv.x*10.0*tau*0.15*clamp(floor(5.0 + 10.0*cos(iTime)), 0.0, 10.0)))* abs(1.0 / (30.0 *uv.y));
 vec3 horBeam = vec3(beamWidth);
gl_FragColor = vec4((( horBeam)* horColour), 1.0);
}

距离场

通过“空间距离”来重新解释什么是图形。这种技巧被称之为“距离场”

// Author @patriciogv - 2015
// http://patriciogonzalezvivo.com

#ifdef GL_ES
precision mediump float;
#endif

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

float circle(in vec2 _st, in float _radius){
    vec2 dist = _st-vec2(0.5);
 return 1.-smoothstep(_radius-(_radius*0.01),
                         _radius+(_radius*0.01),
                         dot(dist,dist)*4.0);
}

void main(){
 vec2 st = gl_FragCoord.xy/u_resolution.xy;

 vec3 color = vec3(circle(st,0.9));

 gl_FragColor = vec4( color, 1.0 );
}

#ifdef GL_ES
precision mediump float;
#endif

#define PI 3.14159265359
#define TWO_PI 6.28318530718

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

// Reference to
// http://thndl.com/square-shaped-shaders.html

void main(){
  vec2 st = gl_FragCoord.xy/u_resolution.xy;
  st.x *= u_resolution.x/u_resolution.y;
  vec3 color = vec3(0.0);
  float d = 0.0;

  // Remap the space to -1. to 1.
  st = st *2.-1.;

  // Number of sides of your shape
  int N = 3;

  // Angle and radius from the current pixel
  float a = atan(st.x,st.y)+PI;
  float r = TWO_PI/float(N);

  // Shaping function that modulate the distance
  d = cos(floor(.5+a/r)*r-a)*length(st);

  color = vec3(1.0-smoothstep(.4,.41,d));
  // color = vec3(d);

  gl_FragColor = vec4(color,1.0);
}

极坐标下的图形

y = cos(x*3.);
//y = abs(cos(x*3.));
//y = abs(cos(x*2.5))*0.5+0.3;
//y = abs(cos(x*12.)*sin(x*3.))*.8+.1;
//y = smoothstep(-.5,1., cos(x*10.))*0.2+0.5;

// Author @patriciogv - 2015
// http://patriciogonzalezvivo.com

#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);

    vec2 pos = vec2(0.5)-st;

    float r = length(pos)*2.0;
    float a = atan(pos.y,pos.x);

    float f = cos(a*3.);
    // f = abs(cos(a*3.));
    // f = abs(cos(a*2.5))*.5+.3;
    // f = abs(cos(a*12.)*sin(a*3.))*.8+.1;
    // f = smoothstep(-.5,1., cos(a*10.))*0.2+0.5;

    color = vec3( 1.-smoothstep(f,f+0.02,r) );

    gl_FragColor = vec4(color, 1.0);
}