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optimisations from bevyengine#3984 + comments
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@robtfm
robtfm committed Feb 19, 2022
1 parent d8f4216 commit fe967ae
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Showing 2 changed files with 36 additions and 33 deletions.
52 changes: 31 additions & 21 deletions crates/bevy_pbr/src/light.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -205,13 +205,19 @@ pub enum SimulationLightSystems {

#[derive(Debug, Copy, Clone)]
pub enum ClusterFarZMode {
// use the camera far-plane to determine the Z-depth of the furthest cluster layer
CameraFarPlane,
// calculate the required maximum Z-depth based on currently visible lights.
// Culls lights from fragments better, speeding up GPU lighting operations
// at the expense of some CPU time as the cluster index list is better filled.
MaxLightRange,
// constant max Z-depth
Constant(f32),
}

#[derive(Debug, Copy, Clone)]
pub struct ClusterZConfig {
// far depth of the nearest cluster layer
pub first_slice_depth: f32,
pub far_z_mode: ClusterFarZMode,
}
Expand All @@ -220,16 +226,17 @@ impl Default for ClusterZConfig {
fn default() -> Self {
Self {
first_slice_depth: 5.0,
far_z_mode: ClusterFarZMode::CameraFarPlane,
far_z_mode: ClusterFarZMode::MaxLightRange,
}
}
}

#[derive(Debug, Copy, Clone, Component)]
pub enum ClusterConfig {
// one single cluster
// one single cluster. Optimal for low-light complexity scenes or scenes where
// most lights impact the entire scene
Single,
// explicit x, y and z counts (may yield non-square x/y clusters)
// explicit x, y and z counts (may yield non-square x/y clusters depending on aspect ratio)
XYZ {
dimensions: UVec3,
z_config: ClusterZConfig,
Expand All @@ -246,7 +253,7 @@ pub enum ClusterConfig {
impl Default for ClusterConfig {
fn default() -> Self {
// 24 depth slices, square clusters with at most 4096 total clusters
// use camera far plane as clusters max extent, first slice extends to 5.0
// use max light distance as clusters max Z-depth, first slice extends to 5.0
Self::FixedZ {
total: 4096,
z_slices: 24,
Expand Down Expand Up @@ -572,10 +579,6 @@ fn ndc_position_to_cluster(
.clamp(UVec3::ZERO, cluster_dimensions - UVec3::ONE)
}

fn cluster_to_index(cluster_dimensions: UVec3, cluster: UVec3) -> usize {
((cluster.y * cluster_dimensions.x + cluster.x) * cluster_dimensions.z + cluster.z) as usize
}

// Calculate an AABB for the light in view space, returns a (Vec3, Vec3) containing min and max with
// - x and y in view space with range [-1, 1]
// - z in world space with view orientation, with range [-inf, -0.0001] for perspective, and [1.0000, inf] for orthographic
Expand Down Expand Up @@ -697,7 +700,7 @@ pub fn assign_lights_to_clusters(
let screen_size_u32 = UVec2::new(window.physical_width(), window.physical_height());
let mut cluster_dimensions = config.dimensions_for_screen_size(screen_size_u32);

let first_slice_cutoff = config.first_slice_depth();
let first_slice_depth = config.first_slice_depth();
let far_z = match config.far_z_mode() {
ClusterFarZMode::CameraFarPlane => camera.far,
ClusterFarZMode::MaxLightRange => {
Expand All @@ -716,7 +719,7 @@ pub fn assign_lights_to_clusters(

let cluster_factors = calculate_cluster_factors(
// NOTE: Using the special cluster near value
first_slice_cutoff,
first_slice_depth,
far_z,
cluster_dimensions.z as f32,
is_orthographic,
Expand Down Expand Up @@ -771,20 +774,22 @@ pub fn assign_lights_to_clusters(
// add one to each axis to ensure at least 1 whole tile is counted per light / account for overlap
cluster_index_estimate += (xy_count.x + 1.0) * (xy_count.y + 1.0) * z_count as f32;

// record number of corner indexes we've added
corner_index_count += z_count as f32;
}

let mut index_estimate = cluster_index_estimate as usize;
if cluster_index_estimate > ViewClusterBindings::MAX_INDICES as f32 {
// scale x and y cluster count to be able to fit all our indices

// we take the ratio of the index estimate less one index per light.
// we take the ratio of the index estimate less one index per light per z-layer
// over the total available indices less one index per light per z-layer.
// we can do this as the number of overlapped clusters are proportional to the tile size
// except for the additional corner cluster of which there's exactly one per light.
let estimate_without_corner = cluster_index_estimate - corner_index_count;
let max_without_corner = ViewClusterBindings::MAX_INDICES as f32 - corner_index_count;
let estimate_without_corners = cluster_index_estimate - corner_index_count;
let max_without_corners = ViewClusterBindings::MAX_INDICES as f32 - corner_index_count;

let index_ratio = max_without_corner / estimate_without_corner;
let index_ratio = max_without_corners / estimate_without_corners;
let xy_ratio = index_ratio.sqrt();

cluster_dimensions.x = ((cluster_dimensions.x as f32 * xy_ratio).floor() as u32).max(1);
Expand All @@ -797,14 +802,14 @@ pub fn assign_lights_to_clusters(
camera,
cluster_dimensions,
&mut clusters,
first_slice_cutoff,
first_slice_depth,
far_z,
);
let cluster_count = clusters.aabbs.len();

let mut clusters_lights =
vec![VisiblePointLights::from_light_count(light_count); cluster_count];
let mut visible_lights_set = HashSet::with_capacity(light_count);
let mut visible_lights = Vec::with_capacity(light_count);

for (light_entity, light_transform, light) in lights.iter() {
let light_sphere = Sphere {
Expand All @@ -817,6 +822,10 @@ pub fn assign_lights_to_clusters(
continue;
}

// NOTE: The light intersects the frustum so it must be visible and part of the global set
global_lights_set.insert(light_entity);
visible_lights.push(light_entity);

// note: caching seems to be slower than calling twice for this aabb calculation
let (light_aabb_ndc_min, light_aabb_ndc_max) = viewspace_light_aabb(
is_orthographic,
Expand All @@ -843,14 +852,14 @@ pub fn assign_lights_to_clusters(
(min_cluster.min(max_cluster), min_cluster.max(max_cluster));

for y in min_cluster.y..=max_cluster.y {
let row_offset = y * clusters.axis_slices.x;
for x in min_cluster.x..=max_cluster.x {
let col_offset = (row_offset + x) * clusters.axis_slices.z;
for z in min_cluster.z..=max_cluster.z {
let cluster_index =
cluster_to_index(clusters.axis_slices, UVec3::new(x, y, z));
// NOTE: cluster_index = (y * dim.x + x) * dim.z + z
let cluster_index = (col_offset + z) as usize;
let cluster_aabb = &clusters.aabbs[cluster_index];
if light_sphere.intersects_obb(cluster_aabb, &view_transform) {
global_lights_set.insert(light_entity);
visible_lights_set.insert(light_entity);
clusters_lights[cluster_index].entities.push(light_entity);
index_count += 1;
}
Expand All @@ -864,8 +873,9 @@ pub fn assign_lights_to_clusters(
}

clusters.lights = clusters_lights;
visible_lights.shrink_to_fit();
commands.entity(view_entity).insert(VisiblePointLights {
entities: visible_lights_set.into_iter().collect(),
entities: visible_lights,
index_count,
index_estimate,
});
Expand Down
17 changes: 5 additions & 12 deletions examples/3d/lighting.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,10 +13,10 @@ fn main() {
App::new()
.insert_resource(Msaa { samples: 4 })
.insert_resource(WindowDescriptor {
// width: 1280.0,
// height: 720.0,
width: 1280.0,
height: 720.0,
present_mode: PresentMode::Mailbox,
mode: WindowMode::BorderlessFullscreen,
// mode: WindowMode::BorderlessFullscreen,
..Default::default()
})
.add_plugins(DefaultPlugins)
Expand Down Expand Up @@ -327,13 +327,6 @@ fn cluster_style(
) {
let configs = vec![
ClusterConfig::Single,
ClusterConfig::XYZ {
dimensions: UVec3::new(30, 5, 24),
z_config: ClusterZConfig {
first_slice_depth: 5.0,
far_z_mode: ClusterFarZMode::CameraFarPlane,
},
},
ClusterConfig::FixedZ {
total: 4096,
z_slices: 24,
Expand All @@ -351,15 +344,15 @@ fn cluster_style(
},
},
ClusterConfig::FixedZ {
total: 512,
total: 1024,
z_slices: 10,
z_config: ClusterZConfig {
first_slice_depth: 5.0,
far_z_mode: ClusterFarZMode::CameraFarPlane,
},
},
ClusterConfig::FixedZ {
total: 512,
total: 1024,
z_slices: 10,
z_config: ClusterZConfig {
first_slice_depth: 5.0,
Expand Down

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