Advanced Programming with OpenGL ES 3.0 - Praise for OpenGL ES 30 Programming Guide - page 406

Example 14-19 Checker Fragment Shader with Conditional Checks

#version 300 es
precision mediump float;

// frequency of the checkerboard pattern
uniform int u_frequency;

in vec2 v_st;
layout(location = 0) out vec4 outColor;

void main()
{
vec2 tcmod = mod(v_st * float(u_frequency), 1.0);

if(tcmod.s < 0.5)
{
if(tcmod.t < 0.5)
outColor = vec4(1.0);
else
outColor = vec4(0.0);
}
else
{
if(tcmod.t < 0.5)
outColor = vec4(0.0);
else
outColor = vec4(1.0);
}
}

Example 14-20 Checker Fragment Shader without Conditional Checks

#version 300 es
precision mediump float;

// frequency of the checkerboard pattern
uniform int u_frequency;

in vec2 v_st;
layout(location = 0) out vec4 outColor;

void
main()
{
vec2 texcoord = mod(floor(v_st * float(u_frequency * 2)),2.0);
float delta = abs(texcoord.x − texcoord.y);
outColor = mix(vec4(1.0), vec4(0.0), delta);
}