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Integrate decoupled color into the live reservoir #191

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Integrate decoupled color into the live reservoir #191

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56 changes: 37 additions & 19 deletions blade-render/code/ray-trace.wgsl
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ const PI: f32 = 3.1415926;
const MAX_RESERVOIRS: u32 = 2u;
// See "DECOUPLING SHADING AND REUSE" in
// "Rearchitecting Spatiotemporal Resampling for Production"
const DECOUPLED_SHADING: bool = false;
const DECOUPLED_SHADING: bool = true;

// We are considering 2x2 grid, so must be <= 4
const FACTOR_TEMPORAL_CANDIDATES: u32 = 1u;
Expand Down Expand Up @@ -68,7 +68,9 @@ struct LiveReservoir {
selected_uv: vec2<f32>,
selected_light_index: u32,
selected_target_score: f32,
selected_radiance: vec3<f32>,
/// In `DECOUPLED_SHADING`, this is the aggregate evaluated color.
/// Otherwise, it's the selected sample evaluated color.
color: vec3<f32>,
weight_sum: f32,
history: f32,
}
Expand Down Expand Up @@ -96,22 +98,34 @@ fn bump_reservoir(r: ptr<function, LiveReservoir>, history: f32) {
}
fn make_reservoir(ls: LightSample, light_index: u32, brdf: vec3<f32>) -> LiveReservoir {
var r: LiveReservoir;
r.selected_radiance = ls.radiance * brdf;
let color = ls.radiance * brdf;
r.selected_uv = ls.uv;
r.selected_light_index = light_index;
r.selected_target_score = compute_target_score(r.selected_radiance);
r.weight_sum = r.selected_target_score / ls.pdf;
r.selected_target_score = compute_target_score(color);
let contribution_weight = 1.0 / ls.pdf;
r.weight_sum = r.selected_target_score * contribution_weight;
r.history = 1.0;
r.color = color;
if (DECOUPLED_SHADING) {
r.color *= r.weight_sum * contribution_weight;
}
return r;
}
fn merge_reservoir(r: ptr<function, LiveReservoir>, other: LiveReservoir, random: f32) -> bool {
(*r).weight_sum += other.weight_sum;
(*r).history += other.history;
if (DECOUPLED_SHADING) {
let denom = other.selected_target_score * other.history;
let contribution_weight = select(0.0, other.weight_sum / denom, denom > 0.0);
(*r).color += other.weight_sum * other.color * contribution_weight;
}
if ((*r).weight_sum * random < other.weight_sum) {
(*r).selected_light_index = other.selected_light_index;
(*r).selected_uv = other.selected_uv;
(*r).selected_target_score = other.selected_target_score;
(*r).selected_radiance = other.selected_radiance;
if (!DECOUPLED_SHADING) {
(*r).color = other.color;
}
return true;
} else {
return false;
Expand All @@ -122,17 +136,26 @@ fn normalize_reservoir(r: ptr<function, LiveReservoir>, history: f32) {
if (h > 0.0) {
(*r).weight_sum *= history / h;
(*r).history = history;
if (DECOUPLED_SHADING) {
(*r).color *= history / h;
}
} else {
(*r).weight_sum = 0.0;
(*r).color = vec3<f32>(0.0);
}
}
fn unpack_reservoir(f: StoredReservoir, max_history: u32, radiance: vec3<f32>) -> LiveReservoir {
fn unpack_reservoir(f: StoredReservoir, max_history: u32, color: vec3<f32>) -> LiveReservoir {
var r: LiveReservoir;
r.selected_light_index = f.light_index;
r.selected_uv = f.light_uv;
r.selected_target_score = f.target_score;
r.selected_radiance = radiance;
let history = min(f.confidence, f32(max_history));
r.weight_sum = f.contribution_weight * f.target_score * history;
r.history = history;
r.color = color;
if (DECOUPLED_SHADING) {
r.color *= r.weight_sum * f.contribution_weight;
}
return r;
}
fn pack_reservoir_detail(r: LiveReservoir, denom_factor: f32) -> StoredReservoir {
Expand Down Expand Up @@ -470,17 +493,16 @@ fn compute_restir(surface: Surface, pixel: vec2<i32>, rng: ptr<function, RandomS
other.selected_light_index = neighbor.light_index;
other.selected_uv = neighbor.light_uv;
other.selected_target_score = t_neighbor_at_canonical.score;
other.selected_radiance = t_neighbor_at_canonical.color;
other.color = t_neighbor_at_canonical.color;
other.weight_sum = t_neighbor_at_canonical.score * neighbor.contribution_weight * mis_neighbor;
if (DECOUPLED_SHADING) {
other.color *= other.weight_sum * neighbor.contribution_weight;
}
} else {
let radiance = evaluate_reflected_light(surface, other.selected_light_index, other.selected_uv);
other = unpack_reservoir(neighbor, max_history, radiance);
}

if (DECOUPLED_SHADING) {
let color = neighbor.contribution_weight * other.selected_radiance;
color_and_weight += other.weight_sum * vec4<f32>(color, 1.0);
}
if (other.weight_sum <= 0.0) {
bump_reservoir(&reservoir, other.history);
} else {
Expand All @@ -492,20 +514,16 @@ fn compute_restir(surface: Surface, pixel: vec2<i32>, rng: ptr<function, RandomS
if (parameters.use_pairwise_mis != 0) {
normalize_reservoir(&canonical, mis_canonical);
}
if (DECOUPLED_SHADING) {
let cw = canonical.weight_sum / max(canonical.selected_target_score, 0.1);
color_and_weight += canonical.weight_sum * vec4<f32>(cw * canonical.selected_radiance, 1.0);
}
merge_reservoir(&reservoir, canonical, random_gen(rng));

let effective_history = select(reservoir.history, 1.0, parameters.use_pairwise_mis != 0);
let stored = pack_reservoir_detail(reservoir, effective_history);
reservoirs[pixel_index] = stored;
var ro = RestirOutput();
if (DECOUPLED_SHADING) {
ro.radiance = color_and_weight.xyz / max(color_and_weight.w, 0.001);
ro.radiance = reservoir.color / max(reservoir.weight_sum, 0.001);
} else {
ro.radiance = stored.contribution_weight * reservoir.selected_radiance;
ro.radiance = stored.contribution_weight * reservoir.color;
}
return ro;
}
Expand Down