Ray
Let's assume that the lower left corner of the screen corresponds to (-1.0, -1.0) and the upper right corner is (1.0, 1.0). The z coordinate is 0.0:
A ray extends from the origin O to the point with coordinates of the current fragment:
Calculate the length of the ray for each fragment and output the value as the red color channel. Consider the aspect ratio of the screen.
uniform vec2 iResolution;
uniform float iTime;
vec3 getRayOrigin() {
// we move the ray origin around the circle
// to create the animation.
return vec3(cos(iTime) * 0.5, sin(iTime) * 0.5, 0.1);
}
void main() {
vec2 uv = gl_FragCoord.xy / iResolution.xy;
vec3 rayOrigin = getRayOrigin();
gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
}
