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-rw-r--r--shaders/compute.comp334
1 files changed, 183 insertions, 151 deletions
diff --git a/shaders/compute.comp b/shaders/compute.comp
index fa69504..7454589 100644
--- a/shaders/compute.comp
+++ b/shaders/compute.comp
@@ -1,26 +1,35 @@
+// ----------------------------------------------------------------------
+// Most of the BRDF stuff in this code comes from github.com/boksajak/referencePT
+// This repo is used it Ray Tracing gems 2, reference path tracer chaper
+// ----------------------------------------------------------------------
+
#extension GL_EXT_buffer_reference : require
#extension GL_EXT_nonuniform_qualifier : require
layout(local_size_x = 8, local_size_y = 8, local_size_z = 1) in;
+// Specifies minimal reflectance for dielectrics (when metalness is zero)
+// Nothing has lower reflectance than 2%, but we use 4% to have consistent results with UE4, Frostbite, et al.
+#define MIN_DIELECTRICS_F0 0.04f
+
struct ray {
vec3 origin;
vec3 direction;
+ float min_t;
+ float max_t;
};
const float PI = 3.141592653589793;
-const uint LAMBERTIAN_MATERIAL = 0;
-const uint METAL_MATERIAL = 1;
-const uint DIELECTRIC_MATERIAL = 2;
-const uint EMISSIVE_MATERIAL = 3;
+
+const uint DIFFUSE = 1;
+const uint SPECULAR = 2;
struct material {
vec4 albedo;
vec4 emissive;
- float fuzz;
- float ior;
- uint type;
- uint padding;
+ float metalness;
+ float roughness;
+ uint[2] padding;
};
struct hit_info {
@@ -28,7 +37,6 @@ struct hit_info {
vec3 point;
vec3 normal;
material mat;
- bool front_face;
};
struct sphere {
@@ -74,20 +82,19 @@ layout(buffer_reference) readonly buffer scene_metadata {
camera cam;
uint max_bounce;
+ uint min_bounce;
uint width;
uint height;
uint sample_index;
- // uint spheres_count;
- uint triangles_count;
- bool enable_dof;
- bool debug_bvh;
- uint downscale_factor;
+ uint enable_dof;
+ uint debug_bvh;
+ int downscale_factor;
};
layout(buffer_reference) readonly buffer primitives_array {
- // sphere[] spheres;
- triangle triangles[];
+ sphere[] spheres;
+ // triangle triangles[];
};
layout(buffer_reference) readonly buffer nodes_array {
@@ -105,10 +112,6 @@ layout(push_constant) uniform buffers {
uint padding[2];
} bufs;
-vec3 at(ray r, float t) {
- return r.origin + r.direction * t;
-}
-
uint pcg_hash(inout uint seed)
{
uint state = seed;
@@ -122,15 +125,7 @@ float rand(inout uint seed)
return float(pcg_hash(seed)) / 4294967296.0;
}
-vec3 unit_vec(inout uint seed) {
- float z = rand(seed) * 2.0 - 1.0;
- float a = 2.0 * PI * rand(seed);
- float r = sqrt(1.0 - z * z);
-
- return vec3(cos(a) * r, sin(a) * r, z);
-}
-
-vec3 diffuse_reflection_cosine_weighted(inout uint seed) {
+vec3 sample_hemisphere(inout uint seed) {
float r = rand(seed);
float radius = sqrt(r);
float theta = 2.0 * PI * rand(seed);
@@ -146,7 +141,36 @@ vec2 disk_vec(inout uint seed) {
return vec2(cos(a) * r, sin(a) * r);
}
-bool hit_aabb(vec3 minimum, vec3 maximum, ray r, float min_t, float max_t) {
+// Calculates rotation quaternion from axis vector to the vector (0, 0, 1)
+// Input vector must be normalized!
+vec4 rotation_to_z_axis(vec3 axis) {
+ // Handle special case when axis is exact or near opposite of (0, 0, 1)
+ if (axis.z < -0.99999f) return vec4(1.0f, 0.0f, 0.0f, 0.0f);
+
+ return normalize(vec4(axis.y, -axis.x, 0.0f, 1.0f + axis.z));
+}
+
+vec4 invert_rotation(vec4 q) {
+ return vec4(-q.xyz, q.w);
+}
+
+// Optimized point rotation using quaternion
+// Source: https://gamedev.stackexchange.com/questions/28395/rotating-vector3-by-a-quaternion
+vec3 rotate_point(vec4 q, vec3 v) {
+ const vec3 q_axis = q.xyz;
+ return 2.0f * dot(q_axis, v) * q_axis + (q.w * q.w - dot(q_axis, q_axis)) * v + 2.0f * q.w * cross(q_axis, v);
+}
+
+vec3 at(ray r, float t) {
+ return r.origin + r.direction * t;
+}
+
+float luminance(vec3 rgb)
+{
+ return dot(rgb, vec3(0.2126f, 0.7152f, 0.0722f));
+}
+
+bool hit_aabb(vec3 minimum, vec3 maximum, ray r) {
const vec3 invdir = 1.0 / r.direction;
const vec3 f = (maximum.xyz - r.origin.xyz) * invdir;
const vec3 n = (minimum.xyz - r.origin.xyz) * invdir;
@@ -154,27 +178,27 @@ bool hit_aabb(vec3 minimum, vec3 maximum, ray r, float min_t, float max_t) {
const vec3 tmax = max(f, n);
const vec3 tmin = min(f, n);
- const float t1 = min(tmax.x, min(tmax.y, tmax.z));
- const float t0 = max(max(tmin.x, max(tmin.y, tmin.z)), 0.0f);
+ const float t1 = min(min(tmax.x, min(tmax.y, tmax.z)), r.max_t);
+ const float t0 = max(max(max(tmin.x, max(tmin.y, tmin.z)), r.min_t), 0.0f);
return t1 >= t0;
}
-uint hit_aabbs(ray r, float min_t, float max_t) {
+uint hit_aabbs(ray r) {
uint hit_count = 0;
int id = 0;
while(id != -1) {
if (bufs.bvh.nodes[id].primitive_id != -1) {
- triangle tri = bufs.geometry.triangles[bufs.bvh.nodes[id].primitive_id];
- vec3 minimum = min(tri.v1.position, min(tri.v2.position, tri.v3.position)).xyz;
- vec3 maximum = max(tri.v1.position, max(tri.v2.position, tri.v3.position)).xyz;
+ // triangle tri = bufs.geometry.triangles[bufs.bvh.nodes[id].primitive_id];
+ // vec3 minimum = min(tri.v1.position, min(tri.v2.position, tri.v3.position)).xyz;
+ // vec3 maximum = max(tri.v1.position, max(tri.v2.position, tri.v3.position)).xyz;
- if (hit_aabb(minimum, maximum, r, min_t, max_t)) {
- hit_count++;
- }
+ // if (hit_aabb(minimum, maximum, r)) {
+ // hit_count++;
+ // }
id = bufs.bvh.nodes[id].next_id;
- } else if (hit_aabb(bufs.bvh.nodes[id].min, bufs.bvh.nodes[id].max, r, min_t, max_t)) {
+ } else if (hit_aabb(bufs.bvh.nodes[id].min, bufs.bvh.nodes[id].max, r)) {
hit_count++;
id++;
} else {
@@ -185,7 +209,7 @@ uint hit_aabbs(ray r, float min_t, float max_t) {
return hit_count;
}
-bool hit_sphere(sphere s, ray r, float min_t, float max_t, out hit_info info) {
+bool hit_sphere(sphere s, ray r, out hit_info info) {
vec3 origin_center = r.origin - s.position.xyz;
float a = dot(r.direction, r.direction);
@@ -199,10 +223,10 @@ bool hit_sphere(sphere s, ray r, float min_t, float max_t, out hit_info info) {
float sqrt_discriminant = sqrt(discriminant);
float root = (-half_b - sqrt_discriminant) / a;
- if (root < min_t || root > max_t) {
+ if (root < r.min_t || root > r.max_t) {
root = (-half_b + sqrt_discriminant) / a;
- if (root < min_t || root > max_t) {
+ if (root < r.min_t || root > r.max_t) {
return false;
}
}
@@ -211,14 +235,14 @@ bool hit_sphere(sphere s, ray r, float min_t, float max_t, out hit_info info) {
info.point = at(r, info.t);
vec3 outward_normal = (info.point - s.position.xyz) / s.radius;
- info.front_face = dot(outward_normal, r.direction) < 0.0;
- info.normal = info.front_face ? outward_normal : -outward_normal;
+ bool front_face = dot(outward_normal, r.direction) < 0.0;
+ info.normal = front_face ? outward_normal : -outward_normal;
info.mat = s.mat;
return true;
}
-bool hit_triangle(triangle tri, ray r, float min_t, float max_t, out hit_info info) {
+bool hit_triangle(triangle tri, ray r, out hit_info info) {
vec3 v2v1 = tri.v2.position.xyz - tri.v1.position.xyz;
vec3 v3v1 = tri.v3.position.xyz - tri.v1.position.xyz;
@@ -230,175 +254,183 @@ bool hit_triangle(triangle tri, ray r, float min_t, float max_t, out hit_info in
float v = d * dot(q, v2v1);
float t = d * dot(-normal, originv1);
- if (u < 0.0 || u > 1.0 || v < 0.0 || u + v > 1.0 || t < min_t || t > max_t) {
+ if (u < 0.0 || u > 1.0 || v < 0.0 || u + v > 1.0 || t < r.min_t || t > r.max_t) {
return false;
}
info.t = t;
- info.point = at(r, info.t);
-
- // vec3 outward_normal = normal;
- // info.front_face = dot(outward_normal, r.direction) < 0.0;
info.normal = normal;
- // info.mat = material(vec4(u, v, 0.0, 0.0), vec4(0.0), 1.0, 1.5, LAMBERTIAN_MATERIAL, 0);
- info.mat = material(vec4(0.55), vec4(0.0), 1.0, 1.5, LAMBERTIAN_MATERIAL, 0);
return true;
}
-bool hit_node(ray r, float min_t, float max_t, out hit_info info) {
+bool hit_node(ray r, out hit_info info) {
hit_info temp_info;
- float closest_t = max_t;
bool hit = false;
int id = 0;
while(id != -1) {
// Leafs
if (bufs.bvh.nodes[id].primitive_id != -1) {
- // if (hit_sphere(spheres[bufs.bvh.nodes[id].primitive_id], r, min_t, closest_t, temp_info)) {
- // info = temp_info;
- // closest_t = temp_info.t;
- // hit = true;
- // }
- if (hit_triangle(bufs.geometry.triangles[bufs.bvh.nodes[id].primitive_id], r, min_t, closest_t, temp_info)) {
+ if (hit_sphere(bufs.geometry.spheres[bufs.bvh.nodes[id].primitive_id], r, temp_info)) {
info = temp_info;
- closest_t = temp_info.t;
+ r.max_t = temp_info.t;
hit = true;
}
+ // if (hit_triangle(bufs.geometry.triangles[bufs.bvh.nodes[id].primitive_id], r, temp_info)) {
+ // info = temp_info;
+ // r.max_t = temp_info.t;
+ // hit = true;
+ // }
id = bufs.bvh.nodes[id].next_id;
- } else { // Internal nodes
- if (hit_aabb(bufs.bvh.nodes[id].min, bufs.bvh.nodes[id].max, r, min_t, closest_t)) {
+ } else if (hit_aabb(bufs.bvh.nodes[id].min, bufs.bvh.nodes[id].max, r)) {
id++;
- } else {
- id = bufs.bvh.nodes[id].next_id;
- }
+ } else {
+ id = bufs.bvh.nodes[id].next_id;
}
}
+ info.point = at(r, info.t);
return hit;
}
-bool lambertian_scattering(material mat, ray incident, inout uint seed, hit_info info, out vec4 attenuation, out ray scattered) {
- attenuation = mat.albedo;
- scattered = ray(info.point, normalize(info.normal + unit_vec(seed)));
-
- return true;
+vec3 albedo_to_specular_F0(vec3 albedo, float metalness) {
+ return mix(vec3(MIN_DIELECTRICS_F0), albedo, metalness);
}
-bool metal_scattering(material mat, ray incident, inout uint seed, hit_info info, out vec4 attenuation, out ray scattered) {
- vec3 reflected = reflect(normalize(incident.direction), info.normal);
-
- attenuation = mat.albedo;
- scattered = ray(info.point, reflected + mat.fuzz * unit_vec(seed));
-
- return (dot(scattered.direction, info.normal) > 0.0);
+vec3 albedo_to_diffuse_reflectance(vec3 albedo, float metalness) {
+ return albedo * (1.0f - metalness);
}
-float reflectance(float cosine, float eta) {
- // Use Schlick's approximation for reflectance.
- float r0 = (1 - eta) / (1 + eta);
- r0 = r0 * r0;
- return r0 + (1 - r0) * pow((1 - cosine), 5);
+// Schlick's approximation to Fresnel term
+// f90 should be 1.0, except for the trick used by Schuler (see 'shadowedF90' function)
+vec3 eval_fresnel_schlick(vec3 f0, float f90, float NdotS) {
+ return f0 + (f90 - f0) * pow(1.0f - NdotS, 5.0f);
+}
+vec3 eval_fresnel(vec3 f0, float f90, float NdotS) {
+ // Default is Schlick's approximation
+ return eval_fresnel_schlick(f0, f90, NdotS);
}
-bool dielectric_scattering(material mat, ray incident, inout uint seed, hit_info info, out vec4 attenuation, out ray scattered) {
- attenuation = vec4(1.0);
-
- vec3 unit_dir = normalize(incident.direction);
- float cos_theta = min(dot(-unit_dir, info.normal), 1.0);
- float sin_theta = sqrt(1.0 - cos_theta*cos_theta);
+// Attenuates F90 for very low F0 values
+// Source: "An efficient and Physically Plausible Real-Time Shading Model" in ShaderX7 by Schuler
+// Also see section "Overbright highlights" in Hoffman's 2010 "Crafting Physically Motivated Shading Models for Game Development" for discussion
+// IMPORTANT: Note that when F0 is calculated using metalness, it's value is never less than MIN_DIELECTRICS_F0, and therefore,
+// this adjustment has no effect. To be effective, F0 must be authored separately, or calculated in different way. See main text for discussion.
+float shadowed_F90(vec3 F0) {
+ // This scaler value is somewhat arbitrary, Schuler used 60 in his article. In here, we derive it from MIN_DIELECTRICS_F0 so
+ // that it takes effect for any reflectance lower than least reflective dielectrics
+ //const float t = 60.0f;
+ const float t = (1.f / MIN_DIELECTRICS_F0);
+ return min(1.f, t * luminance(F0));
+}
- float eta = info.front_face ? 1.0 / mat.ior : mat.ior;
- vec3 direction;
+float get_brdf_probability(material mat, vec3 view, vec3 shadingNormal) {
+ // Evaluate Fresnel term using the shading normal
+ // Note: we use the shading normal instead of the microfacet normal (half-vector) for Fresnel term here. That's suboptimal for rough surfaces at grazing angles, but half-vector is yet unknown at this point
+ vec3 specular_F0 = vec3(luminance(albedo_to_specular_F0(mat.albedo.rgb, mat.metalness)));
+ float diffuse_reflectance = luminance(albedo_to_diffuse_reflectance(mat.albedo.rgb, mat.metalness));
+ float fresnel = clamp(luminance(eval_fresnel(specular_F0, shadowed_F90(specular_F0), max(0.0f, dot(view, shadingNormal)))), 0.0, 1.0);
- if (eta * sin_theta > 1.0 || reflectance(cos_theta, eta) > rand(seed)) {
- direction = reflect(unit_dir, info.normal);
- } else {
- direction = refract(unit_dir, info.normal, eta);
- }
+ // Approximate relative contribution of BRDFs using the Fresnel term
+ float specular = fresnel;
+ float diffuse = diffuse_reflectance * (1.0f - fresnel); //< If diffuse term is weighted by Fresnel, apply it here as well
- scattered = ray(info.point, direction);
+ // Return probability of selecting specular BRDF over diffuse BRDF
+ float p = (specular / max(0.0001f, (specular + diffuse)));
- return true;
+ // Clamp probability to avoid undersampling of less prominent BRDF
+ return clamp(p, 0.1f, 0.9f);
}
-vec4 ray_color(ray r, uint seed) {
+vec3 ray_color(ray r, uint seed) {
hit_info info;
- uint bounces = 0;
+ vec3 radiance = vec3(0.0);
+ vec3 throughput = vec3(1.0);
- vec4 final_color = vec4(0.0);
- vec4 throughput = vec4(1.0);
- ray current_ray = r;
- while (hit_node(current_ray, 0.001, 1e15, info) && bounces < bufs.scene.max_bounce) {
- ray scattered;
- vec4 attenuation = vec4(0.0);
- // if ((info.mat.type == LAMBERTIAN_MATERIAL && lambertian_scattering(info.mat, current_ray, seed, info, attenuation, scattered)) ||
- // (info.mat.type == METAL_MATERIAL && metal_scattering(info.mat, current_ray, seed, info, attenuation, scattered)) ||
- // (info.mat.type == DIELECTRIC_MATERIAL && dielectric_scattering(info.mat, current_ray, seed, info, attenuation, scattered)) ||
- // info.mat.type == EMISSIVE_MATERIAL) {
- lambertian_scattering(info.mat, current_ray, seed, info, attenuation, scattered);
- // final_color += info.mat.emissive * throughput;
- throughput *= attenuation;
+ for (uint bounce = 0; bounce < bufs.scene.max_bounce; bounce++) {
+ if (!hit_node(r, info))
+ return throughput * vec3(1.0);
- float NdotR = dot(info.normal, scattered.direction);
- float PDF = NdotR / PI;
- vec4 BRDF = attenuation / PI;
- throughput = (throughput * NdotR / PDF) * BRDF;
- current_ray = scattered;
+ // uint brdf_type;
+ // if (info.mat.metalness == 1.f && info.mat.metalness == 0.f) {
+ // brdf_type = SPECULAR;
+ // } else {
+ // float brdf_probability = get_brdf_probability(info.mat, -r.direction, );
+ // if (rand(seed) < brdf_probability) {
+ // brdf_type = SPECULAR;
+ // } else {
+ // brdf_type = DIFFUSE;
+ // }
+ // }
- // Russian Roulette
- // As the throughput gets smaller, the ray is more likely to get terminated early.
- // Survivors have their value boosted to make up for fewer samples being in the average.
- // {
- // float p = max(throughput.r, max(throughput.g, throughput.b));
- // if (rand(seed) > p) {
- // break;
- // }
+ // Move to tangent space
+ vec4 rotation_to_z = rotation_to_z_axis(info.normal);
+ vec3 view_local = rotate_point(rotation_to_z, -r.direction);
+ vec3 normal_local = vec3(0.0, 0.0, 1.0);
+ vec3 ray_dir_local = sample_hemisphere(seed);
- // // Add the energy we 'lose' by randomly terminating paths
- // throughput *= 1.0 / p;
- // }
- // }
- bounces++;
- }
+ float NdotL = dot(normal_local, ray_dir_local);
+ float pdf = NdotL / PI;
+ vec3 brdf = albedo_to_diffuse_reflectance(info.mat.albedo.xyz, info.mat.metalness) / PI;
+ throughput *= brdf / pdf;
- return throughput;
- // return final_color;
-}
+ // Move to global space
+ vec4 rotation_from_z = invert_rotation(rotation_to_z);
+ vec3 ray_dir = rotate_point(rotation_from_z, ray_dir_local);
-void main() {
- uint x = gl_GlobalInvocationID.x * bufs.scene.downscale_factor;
- uint y = gl_GlobalInvocationID.y * bufs.scene.downscale_factor;
+ r = ray(info.point, normalize(info.normal + ray_dir), 0.001f, 1e15);
- vec2 uv = vec2(float(x) / (bufs.scene.width - 1), 1.0 - (float(y) / (bufs.scene.height - 1)));
+ // Russian Roulette
+ // As the throughput gets smaller, the ray is more likely to get terminated early.
+ // Survivors have their value boosted to make up for fewer samples being in the average.
+ if (bounce > bufs.scene.min_bounce) {
+ float probability = min(0.95f, luminance(throughput));
+ if (probability < rand(seed)) break;
+ throughput /= probability;
+ }
+ }
+
+ return radiance;
+}
- uint seed = uint(x * uint(1973) + y * uint(9277) + bufs.scene.sample_index * uint(26699)) | uint(1);
+ray generate_camera_ray(ivec2 coords, uint seed) {
+ vec2 scene_size = vec2(bufs.scene.width - 1, bufs.scene.height - 1);
+ vec2 uv = vec2(coords.x / scene_size.x, 1.0 - coords.y / scene_size.y);
vec2 rand_disk = disk_vec(seed);
- vec2 jittered_uvs = uv + vec2(rand(seed) / (bufs.scene.width - 1), rand(seed) / (bufs.scene.height - 1));
+ vec2 jittered_uvs = uv + vec2(rand(seed), rand(seed)) / scene_size;
vec2 lens_disk = vec2(0.0);
- if (bufs.scene.enable_dof) {
+
+ if (bufs.scene.enable_dof == 1) {
lens_disk = rand_disk * bufs.scene.cam.lens_radius;
}
vec3 offset = lens_disk.x * bufs.scene.cam.right.xyz + lens_disk.y * bufs.scene.cam.up.xyz;
- vec4 proj_plane_pos = bufs.scene.cam.first_pixel + jittered_uvs.x * bufs.scene.cam.horizontal + jittered_uvs.y * bufs.scene.cam.vertical;
+ vec3 proj_plane_pos = bufs.scene.cam.first_pixel.xyz + jittered_uvs.x * bufs.scene.cam.horizontal.xyz + jittered_uvs.y * bufs.scene.cam.vertical.xyz;
+
+ return ray(bufs.scene.cam.position.xyz + offset, proj_plane_pos.xyz - bufs.scene.cam.position.xyz - offset, 0.001f, 1e15);
+}
+
+void main() {
+ ivec2 coords = ivec2(gl_GlobalInvocationID.xy) * bufs.scene.downscale_factor;
- ray r = ray(bufs.scene.cam.position.xyz + offset, proj_plane_pos.xyz - bufs.scene.cam.position.xyz - offset);
- vec4 out_color = vec4(0.0);
+ uint seed = uint(coords.x * uint(1973) + coords.y * uint(9277) + bufs.scene.sample_index * uint(26699)) | uint(1);
+ ray r = generate_camera_ray(coords, seed);
- if (bufs.scene.debug_bvh) {
- out_color = hit_aabbs(r, 0.001, 1e15) * vec4(0.001, 0.0, 0.0, 1.0);
+ vec3 out_color = vec3(0.0);
+ if (bufs.scene.debug_bvh == 1) {
+ out_color = hit_aabbs(r) * vec3(0.001, 0.0, 0.0);
} else {
out_color = ray_color(r, seed);
}
float spp_scale = (1.0 / bufs.scene.sample_index);
- vec4 acc_color = imageLoad(images[nonuniformEXT(bufs.accumulation_image_index)], ivec2(x, y));
- out_color = vec4(mix(acc_color, out_color, spp_scale));
+ vec3 acc_color = imageLoad(images[nonuniformEXT(bufs.accumulation_image_index)], coords).xyz;
+ out_color = mix(acc_color, out_color, spp_scale);
for (uint i = 0; i < bufs.scene.downscale_factor; i++) {
for (uint j = 0; j < bufs.scene.downscale_factor; j++) {
- imageStore(images[nonuniformEXT(bufs.output_image_index)], ivec2(x + i, y + j), out_color);
+ imageStore(images[nonuniformEXT(bufs.output_image_index)], coords + ivec2(i, j), vec4(out_color, 1.0));
}
}
}
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