Shader特效——“Point in Box”的实现 【GLSL】

uniform sampler2D texUnit;

float insideBox(vec2 v, vec2 bottomLeft, vec2 topRight)
{
// 如果在矩形内的话，s应该为(1.， 1.)，即函数返回值应该为 1
vec2 s = step(bottomLeft, v) - step(topRight, v);
return s.x * s.y;
}

void main()
{
vec4 color = vec4(.6, .3, .5, 1.);
vec2 texCoord = gl_FragCoord.xy/vec2(512., 512.);

float t = insideBox(texCoord, vec2(0.5, 0.5), vec2(1, 1));

gl_FragColor = t * color;
}