A little toolkit for single-quad fragment shader demos
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#version 330 core
#define FOV 90
#define EPSILON 0.01
#define MAX_STEPS 64
#define NEAR_D 0.
#define FAR_D 20.
#define GRAD_EPSILON 0.0001
#define saturate(x) clamp(x, 0, 1)
uniform vec2 u_Resolution;
uniform vec4 u_Mouse;
uniform float u_Time;
out vec4 color;
#include "utils.glsl"
#include "march_prolog.glsl"
#include "hg_sdf.glsl"
#include "colormap_cool.glsl"
vec3 ray_dir(float fov, vec2 uv) {
float z = 1./tan(radians(fov)/2.);
return normalize(vec3(uv, z));
}
SceneResult scene_f(vec3 p) {
SceneResult box = SceneResult(fBox(p, vec3(1)), 1.);
SceneResult sphere = SceneResult(fSphere(p + vec3(1), 1.0), 2.);
return min_sr(box, sphere);
}
vec3 estimate_scene_normal(vec3 p) {
vec3 dx = vec3(GRAD_EPSILON, 0, 0);
vec3 dy = vec3(0, GRAD_EPSILON, 0);
vec3 dz = vec3(0, 0, GRAD_EPSILON);
return normalize(vec3(
scene_f(p + dx).d - scene_f(p - dx).d,
scene_f(p + dy).d - scene_f(p - dy).d,
scene_f(p + dz).d - scene_f(p - dz).d
));
}
vec3 raymarch(vec3 o, vec3 d, float start, float end) {
float t = start;
for (int i = 0; i < MAX_STEPS; i++) {
SceneResult sr = scene_f(o + d*t);
if (sr.d < EPSILON || t > end)
return vec3(t, sr.mat_idx, i);
t += sr.d;
}
return vec3(end, -1., MAX_STEPS);
}
vec4 shade(vec3 p) {
vec3 normal = estimate_scene_normal(p);
return vec4((normal + vec3(1.0))/2.0, 1.0);
}
void main() {
vec2 mouse_uv = u_Mouse.xy * 2.0 / u_Resolution.xy - 1.0;
vec2 uv = gl_FragCoord.xy * 2.0 / u_Resolution.xy - 1.0;
uv.x *= u_Resolution.x/u_Resolution.y;
float an = 0.3 * u_Time;
float d = 2. + sin(an) * 1.6;
vec3 eye = vec3(3. * sin(an), 2., 3. * cos(an)) * d;
vec3 target = vec3(0., 0., 0.);
mat3 lookAt = look_mat(eye, target, 0);
vec3 dir = normalize(lookAt * ray_dir(FOV, uv));
color = vec4(0.);
vec3 result = raymarch(eye, dir, NEAR_D, FAR_D);
float depth = result.x;
float mat_idx = result.y;
float iters = result.z;
if (depth >= FAR_D) {
color = vec4(1.0, 0.5, 1.0, 1.0);
return;
}
color = colormap(iters/MAX_STEPS+0.5);
vec3 p = eye + dir * depth;
color = shade(p);
}