1#define_import_path bevy_pbr::cluster
2#import bevy_pbr::clustered_forward::view_z_to_z_slice
3
4// Valid values for the `object_type` field.
5const CLUSTERABLE_OBJECT_TYPE_POINT_LIGHT: u32 = 0u;
6const CLUSTERABLE_OBJECT_TYPE_SPOT_LIGHT: u32 = 1u;
7const CLUSTERABLE_OBJECT_TYPE_REFLECTION_PROBE: u32 = 2u;
8const CLUSTERABLE_OBJECT_TYPE_IRRADIANCE_VOLUME: u32 = 3u;
9const CLUSTERABLE_OBJECT_TYPE_DECAL: u32 = 4u;
10
11const NDC_MIN: vec2<f32> = vec2<f32>(-1.0);
12const NDC_MAX: vec2<f32> = vec2<f32>(1.0);
13
14// Metadata stored on GPU that's global to all clusters for a view.
15//
16// See the comments in `bevy_pbr/src/cluster/gpu.rs` for information on the
17// fields.
18struct ClusterMetadata {
19    indirect_draw_params: ClusterRasterIndirectDrawParams,
20
21    clustered_light_count: u32,
22    reflection_probe_count: u32,
23    irradiance_volume_count: u32,
24    decal_count: u32,
25
26    z_slice_list_capacity: u32,
27    index_list_size: u32,
28
29    farthest_z: atomic<u32>,
30};
31
32// Indirect draw parameters in the format required by the WebGPU specification.
33struct ClusterRasterIndirectDrawParams {
34    index_count: u32,
35    instance_count: atomic<u32>,
36    first_index: u32,
37    base_vertex: u32,
38    first_instance: u32,
39}
40
41// The GPU representation of a single Z-slice of a clusterable object.
42//
43// See the comments in `bevy_pbr/src/cluster/gpu.rs` for information on the
44// fields.
45struct ClusterableObjectZSlice {
46    object_index: u32,
47    object_type: u32,
48    z_slice: u32,
49};
50
51// An axis-aligned bounding box.
52struct Aabb {
53    // The minimum extents of the box.
54    min: vec3<f32>,
55    // The maximum extents of the box.
56    max: vec3<f32>,
57};
58
59// An axis-aligned bounding box using unsigned integer coordinates.
60//
61// This is used for cluster bounds.
62struct AabbU {
63    // The minimum extents of the box.
64    min: vec3<u32>,
65    // The maximum extents of the box, plus one.
66    //
67    // We add 1 here so that 0-size AABBs can be expressed.
68    max: vec3<u32>,
69}
70
71// Returns the AABB of an object suitable for conversion into an AABB of
72// clusters.
73//
74// See `bevy_light::cluster::assign::cluster_space_clusterable_object_aabb`.
75fn cluster_space_object_aabb(
76    position: vec3<f32>,
77    radius: f32,
78    view_from_world: mat4x4<f32>,
79    clip_from_view: mat4x4<f32>,
80    view_from_world_scale: vec3<f32>
81) -> Aabb {
82    let position_view = (view_from_world * vec4(position, 1.0)).xyz;
83    let half_extents = radius * abs(view_from_world_scale);
84
85    var view_min = position_view - half_extents;
86    var view_max = position_view + half_extents;
87
88    // Constrain view z to be negative - i.e. in front of the camera
89    // When view z is >= 0.0 and we're using a perspective projection, bad
90    // things happen.  At view z == 0.0, ndc x,y are mathematically undefined.
91    // At view z > 0.0, i.e. behind the camera, the perspective projection flips
92    // the directions of the axes. This breaks assumptions about use of min/max
93    // operations as something that was to the left in view space is now
94    // returning a coordinate that for view z in front of the camera would be on
95    // the right, but at view z behind the camera is on the left. So, we just
96    // constrain view z to be < 0.0 and necessarily in front of the camera.
97    view_min.z = min(view_min.z, -0.00001);
98    view_max.z = min(view_max.z, -0.00001);
99
100    // Is there a cheaper way to do this? The problem is that because of
101    // perspective the point at max z but min xy may be less xy in screenspace,
102    // and similar. As such, projecting the min and max xy at both the closer
103    // and further z and taking the min and max of those projected points
104    // addresses this.
105    let view_xymin_near = view_min;
106    let view_xymin_far = vec3(view_min.xy, view_max.z);
107    let view_xymax_near = vec3(view_max.xy, view_min.z);
108    let view_xymax_far = view_max;
109
110    let clip_xymin_near = clip_from_view * vec4(view_xymin_near, 1.0);
111    let clip_xymin_far = clip_from_view * vec4(view_xymin_far, 1.0);
112    let clip_xymax_near = clip_from_view * vec4(view_xymax_near, 1.0);
113    let clip_xymax_far = clip_from_view * vec4(view_xymax_far, 1.0);
114
115    let ndc_xymin_near = clip_xymin_near.xyz / clip_xymin_near.w;
116    let ndc_xymin_far = clip_xymin_far.xyz / clip_xymin_far.w;
117    let ndc_xymax_near = clip_xymax_near.xyz / clip_xymax_near.w;
118    let ndc_xymax_far = clip_xymax_far.xyz / clip_xymax_far.w;
119
120    var ndc_min = min(min(ndc_xymin_near, ndc_xymin_far), min(ndc_xymax_near, ndc_xymax_far));
121    var ndc_max = max(max(ndc_xymin_near, ndc_xymin_far), max(ndc_xymax_near, ndc_xymax_far));
122
123    // clamp to ndc coords without depth
124    ndc_min = vec3(clamp(ndc_min.xy, NDC_MIN, NDC_MAX), ndc_min.z);
125    ndc_max = vec3(clamp(ndc_max.xy, NDC_MIN, NDC_MAX), ndc_max.z);
126
127    // pack unadjusted z depth into the vecs
128    return Aabb(vec3(ndc_min.xy, view_min.z), vec3(ndc_max.xy, view_max.z));
129}
130
131// Computes the scale of the camera from the view matrix.
132fn compute_view_from_world_scale(world_from_view: mat4x4<f32>) -> vec3<f32> {
133    let world_from_view_3x3 = mat3x3<f32>(
134        world_from_view[0].xyz,
135        world_from_view[1].xyz,
136        world_from_view[2].xyz
137    );
138    let det = determinant(world_from_view_3x3);
139    let scale = vec3<f32>(
140        length(world_from_view_3x3[0]) * sign(det),
141        length(world_from_view_3x3[1]),
142        length(world_from_view_3x3[2])
143    );
144    return vec3<f32>(1.0) / scale;
145}
146
147// Returns the cluster coordinates corresponding to a position in normalized
148// device coordinates.
149// See `bevy_light::cluster::assign::ndc_position_to_cluster`.
150fn ndc_position_to_cluster(
151    cluster_dimensions: vec3<u32>,
152    cluster_factors: vec2<f32>,
153    is_orthographic: bool,
154    ndc_p: vec3<f32>,
155    view_z: f32
156) -> vec3<u32> {
157    let frag_coord = clamp(ndc_p.xy * vec2(0.5, -0.5) + vec2(0.5), vec2(0.0), vec2(1.0));
158    let xy = vec2<u32>(floor(frag_coord * vec2<f32>(cluster_dimensions.xy)));
159    let z_slice = view_z_to_z_slice(cluster_factors, cluster_dimensions.z, view_z, is_orthographic);
160    return clamp(vec3<u32>(xy, z_slice), vec3(0u), cluster_dimensions - vec3(1u));
161}
162
163// Returns the AABB encompassing all clusters that intersect a sphere.
164fn calculate_sphere_cluster_bounds(
165    position: vec3<f32>,
166    radius: f32,
167    view_from_world: mat4x4<f32>,
168    clip_from_view: mat4x4<f32>,
169    view_from_world_scale: vec3<f32>,
170    cluster_dimensions: vec3<u32>,
171    cluster_factors: vec2<f32>,
172    is_orthographic: bool,
173) -> AabbU {
174    let aabb_ndc = cluster_space_object_aabb(
175        position,
176        radius,
177        view_from_world,
178        clip_from_view,
179        view_from_world_scale
180    );
181
182    let temp_min_cluster = ndc_position_to_cluster(
183        cluster_dimensions,
184        cluster_factors,
185        is_orthographic,
186        aabb_ndc.min,
187        aabb_ndc.min.z
188    );
189    let temp_max_cluster = ndc_position_to_cluster(
190        cluster_dimensions,
191        cluster_factors,
192        is_orthographic,
193        aabb_ndc.max,
194        aabb_ndc.max.z
195    );
196
197    let min_cluster = min(temp_min_cluster, temp_max_cluster);
198    let max_cluster = max(temp_min_cluster, temp_max_cluster);
199
200    return AabbU(min_cluster, max_cluster);
201}