Hi!
So I am learning shader code, and I am trying to get Ray Marching to work!
I've gotten pretty far, but I have one small "bug" in the shader and I don't know why it would do this.
The shader is applied to a cube, and it is a simple sphere signed distance function.
When I look at it from the side (aka facing a face) it looks great! But from an angle, I get weird cubic deformations!
I have a gut feeling it has to do with the Camera Origin and ray direction ... ?
Here is the shader code:
shader_type spatial;
render_mode unshaded, cull_disabled;
uniform int NUMBER_OF_STEPS = 32;
//varying vec3 camera_origin;
// params:
// p: arbitrary point in 3D space
// c: the center of our sphere
// r: the radius of our sphere
float distance_from_sphere(in vec3 p, in vec3 c, float r)
{
return length(p - c) - r;
}
float map_the_world(in vec3 p, float time)
{
//float displacement = sin(5.0 * p.x) * sin(5.0 * p.y) * sin(5.0 * p.z) * 0.25;
//displacement *= cos(time);
float sphere_0 = distance_from_sphere(p, vec3(0.0), 1.0);
// Later we might have sphere_1, sphere_2, cube_3, etc...
// return sphere_0 + displacement;
return sphere_0;
}
vec3 calculate_normal(in vec3 p, float time)
{
const vec3 small_step = vec3(0.001, 0.0, 0.0);
float gradient_x = map_the_world(p + small_step.xyy, time) - map_the_world(p - small_step.xyy, time);
float gradient_y = map_the_world(p + small_step.yxy, time) - map_the_world(p - small_step.yxy, time);
float gradient_z = map_the_world(p + small_step.yyx, time) - map_the_world(p - small_step.yyx, time);
vec3 normal = vec3(gradient_x, gradient_y, gradient_z);
return normalize(normal);
}
vec3 ray_march(in vec3 ro, in vec3 rd, float time, out bool hit)
{
float total_distance_traveled = 0.0;
const float MINIMUM_HIT_DISTANCE = 0.001;
const float MAXIMUM_TRACE_DISTANCE = 1000.0;
for (int i = 0; i < NUMBER_OF_STEPS; ++i)
{
vec3 current_position = ro + total_distance_traveled * rd;
float distance_to_closest = map_the_world(current_position, time);
if (distance_to_closest < MINIMUM_HIT_DISTANCE) // hit
{
// Let's return a diffuse from a fake light
vec3 normal = calculate_normal(current_position, time);
// For now, hard-code the light's position in our scene
vec3 light_position = vec3(2.0, -5.0, 3.0);
// Calculate the unit direction vector that points from
// the point of intersection to the light source
vec3 direction_to_light = normalize(current_position - light_position);
float diffuse_intensity = max(0.0, dot(normal, direction_to_light));
hit = true;
return vec3(1.0, 0.0, 0.0) * diffuse_intensity;
}
if (total_distance_traveled > MAXIMUM_TRACE_DISTANCE) // miss
{
break;
}
// accumulate the distance traveled thus far
total_distance_traveled += distance_to_closest;
}
// If we get here, we didn't hit anything so just
// return a background color (black)
hit = false;
return vec3(0.0);
}
void fragment() {
// Get Cameran origin
vec3 ro = (CAMERA_MATRIX * vec4(0.0, 0.0, 0.0, 1.0)).xyz;
// Get Ray direction (From camera to vertex)
vec3 rd = (CAMERA_MATRIX * vec4(VERTEX, 1.0)).xyz;
bool hit;
vec3 color = ray_march(ro, rd, TIME, hit);
if (hit) {
ALBEDO = color;
ALPHA = 1.0;
}
else {
ALPHA = 0.0;
}
}
