WebGL2 Minimal Shaders

quad_ccw.glsl

// both triangles CCW
vec3 quad (int x)
{
  vec3 p = step(vec3(1,2,3),vec3(x%3));
  return mix(p, vec3(p.x-p.y,p.x,0), step(3.,float(x%6)));
}

quad_cw_ccw.glsl

// one triangle CW and one CCW
vec3 quad (int x)
{
  vec3 p = step(vec3(1,2,3),vec3(x%3));
  return mix(p,p.yxz,step(3.,float(x%6)));
}

quad_cw_ccw.vert

// one triangle CW and one CCW
#version 300 es
void main()
{
  vec4 p = step(vec4(1,2,3,0),vec4(x%3));
  return mix(p,p.yxzw,step(3.,float(x%6)));
}

quad_int_cw_ccw.vert

// one triangle CW and one CCW
#version 300 es
void main()
{
  ivec3 p = clamp(ivec3(1,2,0)%(gl_VertexID%3+1),0,1);
  int a = clamp(gl_VertexID%6-2,0,1);
  gl_Position = vec4(p*(1-a)+p.yxz*a,1);
}

triangle.vert

#version 300 es
void main () { gl_Position = step(vec4(1,2,3,0),vec4(gl_VertexID%3)); }

triangle_function.glsl

vec3 triangle (int x) { return step(vec3(1,2,3),vec3(x%3)); }

triangle_int.vert

#version 300 es
void main() { gl_Position = vec4(clamp(ivec3(1,2,0)%(gl_VertexID%3+1),0,1),1); }