+struct Ray {
+ vec3 org, dir;
+ float energy, ior;
+};
+
+struct Material {
+ vec3 diffuse, specular;
+ float shin;
+ float refl, refr;
+ float ior;
+};
+
+struct HitPoint {
+ float dist;
+ vec3 pos, norm;
+ vec2 surfpos;
+ Material mtl;
+ float shadow; /* opacity along the line of sight up to dist=1 */
+};
+
varying vec3 v_rorg, v_rdir;
-vec3 shade(in vec3 pos, in vec3 norm);
+
+vec3 shade(in vec3 ro, in vec3 rd, in HitPoint hit);
vec3 backdrop(in vec3 dir);
-float isect_plane(in vec3 ro, in vec3 rd, out vec3 norm_ret);
+
+bool isect_scene(in vec3 ro, in vec3 rd, out HitPoint hit);
+
+bool isect_floor(in vec3 ro, in vec3 rd, in vec2 sz, out HitPoint hit);
+bool isect_plane(in vec3 ro, in vec3 rd, in vec4 plane, out HitPoint hit);
+bool isect_sphere(in vec3 ro, in vec3 rd, in vec3 pos, float rad, out HitPoint hit);
+
+/* schlick's approximation: [5.0, 1.0, R(0deg)] */
+float hack_fresnel(vec3 i, vec3 n, vec3 fresnel_val);
+
+vec3 tex_chess(in vec3 col1, in vec3 col2, in vec2 spos);
+
+#define GREY(x) vec3(x, x, x)
+
+const Material mtl_sph = Material(vec3(0.05, 0.15, 0.08), GREY(0.8), 80.0, 0.8, 0.0, 0.0);
+const Material mtl_glass = Material(GREY(0.02), GREY(0.8), 80.0, 0.99, 0.99, 1.52);
+const Material mtl_air = Material(GREY(0.0), GREY(0.8), 80.0, 0.99, 0.99, 1.0);
+const Material mtl_floor = Material(GREY(0.5), GREY(0.0), 1.0, 0.0, 0.0, 0.0);
+
+const vec3 light_pos = vec3(-10, 50, 30);
+
+bool cast_ray(in Ray ray, inout vec3 color, out HitPoint hit)
+{
+ if(isect_scene(ray.org, ray.dir, hit)) {
+ color += shade(ray.org, ray.dir, hit) * ray.energy;
+ return true;
+ }
+ color += backdrop(ray.dir) * ray.energy;
+ return false;
+}
+
+#define MAX_LEVEL 8
+
+struct StackFrame {
+ int op;
+ Ray ray;
+ HitPoint hit;
+};
void main()
{
- vec3 rdir = normalize(v_rdir);
+ StackFrame stack[MAX_LEVEL];
+
+ vec3 color = vec3(0.0, 0.0, 0.0);
+
+ stack[0].op = 0;
+ stack[0].ray.org = v_rorg;
+ stack[0].ray.dir = normalize(v_rdir);
+ stack[0].ray.energy = stack[0].ray.ior = 1.0;
- float t = isect_floor(v_rorg, rdir);
- if(t >= 0.0) {
- gl_FragColor.rgb = shade(v_rorg + rdir * t, vec3(0.0, 1.0, 0.0));
- } else {
- gl_FragColor.rgb = backdrop(rdir);
+ int top = 0;
+ while(top >= 0) {
+ if(top >= MAX_LEVEL - 1) {
+ color += backdrop(stack[top].ray.dir) * stack[top].ray.energy;
+ top--;
+ continue;
+ }
+ if(stack[top].ray.energy < 1e-3) {
+ top--;
+ continue;
+ }
+
+ if(!cast_ray(stack[top].ray, color, stack[top].hit)) {
+ /* no hit, return */
+ top--;
+ continue;
+ }
+
+ /* found a hit, recurse for reflection/refraction */
+ HitPoint hit = stack[top].hit;
+
+ // 1.0 when entering, 0.0 when leaving
+ float entering = step(0.0, dot(-stack[top].ray.dir, hit.norm));
+ vec3 norm = faceforward(hit.norm, stack[top].ray.dir, hit.norm);
+
+ float fr = hack_fresnel(-stack[top].ray.dir, norm, vec3(5.0, 2.0, 0.01));
+ // fr = 1 everywhere when ior < 0.5 to avoid affecting the metal sphere
+ fr = min(1.0, (1.0 - step(0.5, hit.mtl.ior)) + fr);
+
+ int op = stack[top].op++;
+ if(op == 0) {
+ // reflection
+ float energy = stack[top].ray.energy * hit.mtl.refl * fr;
+ if(energy > 1e-4) {
+ int next = top + 1;
+ stack[next].op = 0;
+ stack[next].ray.org = hit.pos + norm * 1e-5;
+ stack[next].ray.dir = reflect(stack[top].ray.dir, norm);
+ stack[next].ray.energy = energy;
+ top = next;
+ }
+ } else if(op == 1) {
+ // refraction
+ float energy = stack[top].ray.energy * hit.mtl.refr * (1.0 - fr);
+ if(energy > 1e-4) {
+ float next_ior = mix(stack[top - 1].ray.ior, hit.mtl.ior, entering);
+ float ior = stack[top].ray.ior / next_ior;
+ int next = top + 1;
+ stack[next].op = 0;
+ stack[next].ray.org = hit.pos - norm * 1e-5;
+ stack[next].ray.dir = refract(stack[top].ray.dir, norm, ior);
+ stack[next].ray.energy = energy;
+ stack[next].ray.ior = next_ior;
+ top = next;
+ }
+ } else if(op == 2) {
+ // return
+ top--;
+ }
}
- gl_FragColor.a = 1.0;
+
+ gl_FragColor = vec4(color, 1.0);
}
-vec3 shade(in vec3 pos, in vec3 norm)
+vec3 shade(in vec3 ro, in vec3 rd, in HitPoint hit)
{
+ HitPoint shadow_hit;
+ vec3 norm = faceforward(hit.norm, rd, hit.norm);
+ vec3 ldir = light_pos - hit.pos;
+
+ vec3 amb = hit.mtl.diffuse * 0.01;
+
+ isect_scene(hit.pos + norm * 0.01, ldir, shadow_hit);
+
+ vec3 l = normalize(ldir);
+ vec3 v = normalize(-rd);
+ vec3 h = normalize(v + l);
+ float ndotl = max(dot(norm, l), 0.0);
+ float ndoth = max(dot(norm, h), 0.0);
+
+ vec3 lit = hit.mtl.diffuse * ndotl + hit.mtl.specular * pow(ndoth, hit.mtl.shin);
+
+ return amb + lit * shadow_hit.shadow;
}
+#define M_PI 3.1415926
+#define M_2PI (M_PI * 2.0)
+
vec3 backdrop(in vec3 dir)
{
+ return vec3(0.02, 0.38, 0.6) * 0.9;
}
-float isect_floor(in vec3 ro, in vec3 rd)
+#define FLOOR_OFFS vec3(3.0, 0.0, -9.0)
+#define FLOOR_SIZE vec2(5.5, 12.0)
+
+#define REFL_POS vec3(1.36, -0.5, 0.0)
+#define GLASS_POS vec3(0.0, 0.2, 1.2)
+
+bool isect_scene(in vec3 ro, in vec3 rd, out HitPoint hit_res)
{
- float t = isect_plane(ro, rd, vec4(0.0, 1.0, 0.0, -1.0));
- if(t < 0.0) return t;
+ float opacity = 1.0;
+ HitPoint hit, nearest;
- vec3 p = ro + rd * t;
- float d = max(abs(p.x), max(abs(p.y), abs(p.z)));
- if(d >= 1.0) return -1.0;
+ nearest.dist = 10000.0;
+
+ if(isect_sphere(ro, rd, REFL_POS, 0.85, hit)) {
+ nearest = hit;
+ nearest.mtl = mtl_sph;
+ if(hit.dist < 1.0) {
+ opacity *= mtl_sph.refr;
+ }
+ }
+
+ if(isect_sphere(ro, rd, GLASS_POS, 0.9, hit)) {
+ if(hit.dist < nearest.dist) {
+ nearest = hit;
+ nearest.mtl = mtl_glass;
+ }
+ if(hit.dist < 1.0) {
+ opacity *= mtl_glass.refr * 0.25; // XXX hack quarter the refr, fresnel would reduce it drastically
+ }
+ }
- return t;
+ if(isect_sphere(ro, rd, GLASS_POS, 0.86, hit)) {
+ if(hit.dist < nearest.dist) {
+ nearest = hit;
+ nearest.mtl = mtl_air;
+ }
+ }
+
+ if(isect_floor(ro, rd, FLOOR_SIZE, hit) && hit.dist < nearest.dist) {
+ nearest = hit;
+ nearest.mtl = mtl_floor;
+ nearest.mtl.diffuse = tex_chess(vec3(0.25, 0.01, 0.01), vec3(0.3, 0.3, 0.1), hit.surfpos);
+ }
+
+ if(nearest.dist >= 9999.0) {
+ hit_res.shadow = 1.0;
+ return false;
+ }
+
+ hit_res = nearest;
+ hit_res.shadow = opacity;
+ return true;
+}
+
+bool isect_floor(in vec3 ro, in vec3 rd, in vec2 sz, out HitPoint hit)
+{
+ if(!isect_plane(ro - FLOOR_OFFS, rd, vec4(0.0, 1.0, 0.0, -1.8), hit)) {
+ return false;
+ }
+
+ if(abs(hit.pos.x) >= sz.x || abs(hit.pos.z) >= sz.y) {
+ return false;
+ }
+
+ hit.pos += FLOOR_OFFS;
+ hit.surfpos /= sz * 2.0;
+ return true;
+}
+
+bool isect_plane(in vec3 ro, in vec3 rd, in vec4 plane, out HitPoint hit)
+{
+ float ndotrd = dot(rd, plane.xyz);
+
+ if(abs(ndotrd) < 1e-6) {
+ return false;
+ }
+
+ vec3 pp = plane.xyz * plane.w;
+ vec3 pdir = pp - ro;
+ float t = dot(pdir, plane.xyz) / ndotrd;
+
+ if(t < 1e-6) {
+ return false;
+ }
+
+ hit.dist = t;
+ hit.pos = ro + rd * t;
+ hit.norm = plane.xyz;
+ hit.surfpos = hit.pos.xz; /* XXX */
+ return true;
+}
+
+bool isect_sphere(in vec3 ro, in vec3 rd, in vec3 pos, float rad, out HitPoint hit)
+{
+ float a = dot(rd, rd);
+ float b = dot(rd * 2.0, (ro - pos));
+ float c = dot(ro, ro) + dot(pos, pos) - 2.0 * dot(ro, pos) - rad * rad;
+
+ float d = b * b - 4.0 * a * c;
+ if(d < 1e-6) {
+ return false;
+ }
+
+ float t0 = (-b + sqrt(d)) / (2.0 * a);
+ float t1 = (-b - sqrt(d)) / (2.0 * a);
+
+ if(t0 < 0.0) t0 = t1;
+ if(t1 < 0.0) t1 = t0;
+ float t = min(t0, t1);
+
+ if(t < 1e-6) {
+ return false;
+ }
+
+ hit.dist = t;
+ hit.pos = ro + rd * t;
+ hit.norm = normalize(hit.pos - pos);
+ hit.surfpos.x = atan(hit.norm.z, hit.norm.x);
+ hit.surfpos.y = acos(hit.norm.y);
+ return true;
}
-float isect_plane(in vec3 ro, in vec3 rd, in vec4 plane)
+/* schlick's approximation: [5.0, 1.0, R(0deg)] */
+float hack_fresnel(vec3 i, vec3 n, vec3 fresnel_val)
{
+ return fresnel_val.z + pow(1.0 - dot(i, n), fresnel_val.x) * fresnel_val.y;
+}
+
+vec3 tex_chess(in vec3 col1, in vec3 col2, in vec2 spos)
+{
+ float foo = step(0.5, mod(spos.x * 8.0, 1.0)) * 2.0 - 1.0;
+ float bar = step(0.5, mod(spos.y * 12.0, 1.0)) * 2.0 - 1.0;
+
+ float xor = (foo * bar) * 0.5 + 0.5;
+ return mix(col1, col2, xor);
}
projects / demo_prior / blobdiff