scena 1.7.2

A Rust-native scene-graph renderer with typed scene state, glTF assets, and explicit prepare/render lifecycles.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224

use std::collections::{HashMap, HashSet};

use serde_json::{Map, Value};

use crate::scene::recipe::types::SceneRecipeDiagnosticV1;
use crate::scene::recipe::validation::diagnostic;

/// Minimum sphere `segments` for a near-mirror material to read as a smooth
/// reflection. A coarser sphere reveals its polygon facets once the surface
/// becomes a sharp mirror.
pub(super) const MIN_MIRROR_SPHERE_SEGMENTS: u64 = 256;
/// Minimum sphere `rings` paired with [`MIN_MIRROR_SPHERE_SEGMENTS`] for a
/// smooth near-mirror sphere.
const MIN_MIRROR_SPHERE_RINGS: u64 = 192;
/// Effective roughness at or below this is treated as a near mirror.
const MIRROR_ROUGHNESS_MAX: f64 = 0.1;
/// Sphere tessellation assumed when a recipe omits it. Must match the geometry
/// construction default in `scene_host::recipe::authoring::geometry`.
const DEFAULT_SPHERE_SEGMENTS: u64 = 64;
const DEFAULT_SPHERE_RINGS: u64 = 48;

/// Warn when a renderable pairs a near-mirror material with a low-tessellation
/// sphere. A sharp reflection on a coarse sphere shows the polygon facets, so
/// this tells authors (and agents) before a chrome subject renders as a blocky,
/// faceted ball — the mistake is otherwise invisible until the material becomes
/// a mirror.
pub(super) fn validate_reflective_sphere_tessellation(
    object: &Map<String, Value>,
    diagnostics: &mut Vec<SceneRecipeDiagnosticV1>,
) {
    let sphere_tessellation = collect_sphere_tessellation(object.get("geometries"));
    if sphere_tessellation.is_empty() {
        return;
    }
    let mirror_materials = collect_mirror_materials(object.get("materials"));
    if mirror_materials.is_empty() {
        return;
    }
    for (section, label) in [("nodes", "node"), ("instance_sets", "instance set")] {
        let Some(items) = object.get(section).and_then(Value::as_array) else {
            continue;
        };
        for (index, item) in items.iter().enumerate() {
            let Some(item) = item.as_object() else {
                continue;
            };
            let (Some(geometry), Some(material)) = (
                item.get("geometry").and_then(Value::as_str),
                item.get("material").and_then(Value::as_str),
            ) else {
                continue;
            };
            let Some(tessellation) = sphere_tessellation.get(geometry) else {
                continue;
            };
            if !mirror_materials.contains(material)
                || (tessellation.segments >= MIN_MIRROR_SPHERE_SEGMENTS
                    && tessellation.rings >= MIN_MIRROR_SPHERE_RINGS)
            {
                continue;
            }
            diagnostics.push(diagnostic(
                "reflective_sphere_low_tessellation",
                "warning",
                format!("$.{section}[{index}]"),
                format!(
                    "{label} pairs near-mirror material '{material}' with sphere '{geometry}' at \
                     {} segments and {} rings; a sharp reflection will show the sphere's polygon facets",
                    tessellation.segments, tessellation.rings
                ),
                format!(
                    "raise the sphere to at least segments:{MIN_MIRROR_SPHERE_SEGMENTS}, \
                     rings:{MIN_MIRROR_SPHERE_RINGS} for smooth mirror reflections"
                ),
                None,
                false,
            ));
        }
    }
}

#[derive(Debug, Clone, Copy)]
struct SphereTessellation {
    segments: u64,
    rings: u64,
}

fn collect_sphere_tessellation(value: Option<&Value>) -> HashMap<String, SphereTessellation> {
    let mut map = HashMap::new();
    let Some(items) = value.and_then(Value::as_array) else {
        return map;
    };
    for item in items {
        let Some(item) = item.as_object() else {
            continue;
        };
        let Some(id) = item.get("id").and_then(Value::as_str) else {
            continue;
        };
        let Some(primitive) = item.get("primitive").and_then(Value::as_object) else {
            continue;
        };
        if primitive.get("kind").and_then(Value::as_str) != Some("sphere") {
            continue;
        }
        let segments = primitive
            .get("segments")
            .and_then(Value::as_u64)
            .unwrap_or(DEFAULT_SPHERE_SEGMENTS);
        let rings = primitive
            .get("rings")
            .and_then(Value::as_u64)
            .unwrap_or(DEFAULT_SPHERE_RINGS);
        map.insert(id.to_owned(), SphereTessellation { segments, rings });
    }
    map
}

fn collect_mirror_materials(value: Option<&Value>) -> HashSet<String> {
    let mut set = HashSet::new();
    let Some(items) = value.and_then(Value::as_array) else {
        return set;
    };
    for item in items {
        let Some(item) = item.as_object() else {
            continue;
        };
        let Some(id) = item.get("id").and_then(Value::as_str) else {
            continue;
        };
        let is_mirror = item.get("preset").and_then(Value::as_str) == Some("chrome")
            || item
                .get("roughness")
                .and_then(Value::as_f64)
                .is_some_and(|roughness| roughness <= MIRROR_ROUGHNESS_MAX);
        if is_mirror {
            set.insert(id.to_owned());
        }
    }
    set
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;

    fn diagnostics_for(value: Value) -> Vec<SceneRecipeDiagnosticV1> {
        let mut diagnostics = Vec::new();
        validate_reflective_sphere_tessellation(value.as_object().unwrap(), &mut diagnostics);
        diagnostics
    }

    #[test]
    fn warns_when_chrome_material_uses_low_tessellation_sphere() {
        let diagnostics = diagnostics_for(json!({
            "geometries": [{ "id": "ball", "primitive": { "kind": "sphere", "radius": 0.5, "segments": 96 } }],
            "materials": [{ "id": "m", "preset": "chrome" }],
            "nodes": [{ "id": "n", "geometry": "ball", "material": "m" }],
        }));
        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].code, "reflective_sphere_low_tessellation");
        assert_eq!(diagnostics[0].severity, "warning");
    }

    #[test]
    fn warns_when_default_segments_sphere_is_a_mirror() {
        // Omitting segments falls back to the default, which is below the mirror
        // threshold — the most likely agent mistake.
        let diagnostics = diagnostics_for(json!({
            "geometries": [{ "id": "ball", "primitive": { "kind": "sphere", "radius": 0.5 } }],
            "materials": [{ "id": "m", "kind": "pbr_metallic_roughness", "metallic": 1.0, "roughness": 0.02 }],
            "nodes": [{ "id": "n", "geometry": "ball", "material": "m" }],
        }));
        assert_eq!(diagnostics.len(), 1);
    }

    #[test]
    fn warns_when_chrome_preset_has_roughness_override() {
        let diagnostics = diagnostics_for(json!({
            "geometries": [{ "id": "ball", "primitive": { "kind": "sphere", "radius": 0.5, "segments": 96, "rings": 64 } }],
            "materials": [{ "id": "m", "preset": "chrome", "roughness": 0.42 }],
            "nodes": [{ "id": "n", "geometry": "ball", "material": "m" }],
        }));
        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].code, "reflective_sphere_low_tessellation");
    }

    #[test]
    fn no_warning_for_dense_sphere() {
        let diagnostics = diagnostics_for(json!({
            "geometries": [{ "id": "ball", "primitive": { "kind": "sphere", "radius": 0.5, "segments": 256, "rings": 192 } }],
            "materials": [{ "id": "m", "preset": "chrome" }],
            "nodes": [{ "id": "n", "geometry": "ball", "material": "m" }],
        }));
        assert!(diagnostics.is_empty());
    }

    #[test]
    fn warns_when_segments_are_dense_but_rings_are_low() {
        let diagnostics = diagnostics_for(json!({
            "geometries": [{ "id": "ball", "primitive": { "kind": "sphere", "radius": 0.5, "segments": 256 } }],
            "materials": [{ "id": "m", "preset": "chrome" }],
            "nodes": [{ "id": "n", "geometry": "ball", "material": "m" }],
        }));
        assert_eq!(diagnostics.len(), 1);
        assert_eq!(diagnostics[0].code, "reflective_sphere_low_tessellation");
        assert!(
            diagnostics[0].message.contains("256 segments and 48 rings"),
            "{diagnostics:#?}"
        );
    }

    #[test]
    fn no_warning_for_rough_material_on_coarse_sphere() {
        // Matte/rough materials hide facets, so a coarse sphere is fine for them.
        let diagnostics = diagnostics_for(json!({
            "geometries": [{ "id": "ball", "primitive": { "kind": "sphere", "radius": 0.5, "segments": 32 } }],
            "materials": [{ "id": "m", "preset": "metal", "roughness": 0.42 }],
            "nodes": [{ "id": "n", "geometry": "ball", "material": "m" }],
        }));
        assert!(diagnostics.is_empty());
    }
}