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#ifdef GL_ES
precision highp float;
// These are defined by Kodelife, or whatever environment you are using.
uniform float time;
uniform vec2 resolution;
varying vec3 v_normal;
varying vec2 v_texcoord;
// Define some constants
const int steps = 128; // This is the maximum amount a ray can march.
const float smallNumber = 0.001;
const float maxDist = 10.; // This is the maximum distance a ray can travel.
float scene(vec3 position){
// So this is different from the sphere equation above in that I am
// splitting the position into its three different positions
// and adding a 10th of a cos wave to the x position so it oscillates left
// to right and a (positive) sin wave to the z position
// so it will go back and forth.
float sphere = length(
position.x + cos(time)/10.,
position.z+ sin(time) +1.)
// This is different from the ground equation because the UV is only
// between -1 and 1 we want more than 1/2pi of a wave per length of the
// screen so we multiply the position by a factor of 10 inside the trig
// functions. Since sin and cos oscillate between -1 and 1, that would be
// the entire height of the screen so we divide by a factor of 10.
float ground = position.y + sin(position.x * 10.) / 10.
+ cos(position.z * 10.) / 10. + 1.;
// We want to return whichever one is closest to the ray, so we return the
// minimum distance.
return min(sphere,ground);
vec4 trace (vec3 origin, vec3 direction){
float dist = 0.;
float totalDistance = 0.;
vec3 positionOnRay = origin;
for(int i = 0 ; i < steps; i++){
dist = scene(positionOnRay);
// Advance along the ray trajectory the amount that we know the ray
// can travel without going through an object.
positionOnRay += dist * direction;
// Total distance is keeping track of how much the ray has traveled
// thus far.
totalDistance += dist;
// If we hit an object or are close enough to an object,
if (dist < smallNumber){
// return the distance the ray had to travel normalized so be white
// at the front and black in the back.
return 1. - (vec4(totalDistance) / maxDist);
if (totalDistance > maxDist){
return vec4(0.); // Background color.
return vec4(0.);// Background color.
// main is a reserved function that is going to be called first
void main(void)
// We are redefining the UV coordinates (aka texcoords) to be 0,0 in the
// middle of the screen this is because its easier to work with the camera at
// (0,0) instead of (0.5,0.5) for the SDFs
vec2 uv = -1. + 2. * v_texcoord;
// Unfortunately our screens are not square so we must account for that.
uv.x *= (resolution.x / resolution.y);
vec3 rayOrigin = vec3(uv, 0.);
vec3 camOrigin = vec3(0., 0., -1.);
vec3 direction = camOrigin + rayOrigin;
// This reserved variable is what we must set the final color to
gl_FragColor = trace(rayOrigin, direction);
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