Struct LodThresholds 

pub struct LodThresholds {
    pub r_near: f64,
    pub r_mid: f64,
    pub mid_mip_levels: Option<u32>,
    pub mid_mip_scan_dist: Option<i32>,
}

Per-grid LOD picker configuration: world-distance thresholds for tier dispatch + optional Mid-tier render overrides.

Tier dispatch (centre-to-centre distance d):

• d <= r_near → Lod::Near
• r_near < d <= r_mid → Lod::Mid
• d > r_mid → Lod::Far

All thresholds default to f64::INFINITY via Default / Self::always_near, so a freshly-constructed crate::Grid always lands on Lod::Near — the S5-and-earlier byte-stable behaviour. Callers that want real LOD opt in by writing a non-default value into crate::Grid::lod_thresholds.

NaN thresholds are treated as “always Lod::Far” because every d <= NaN comparison is false. No assert — callers shouldn’t be passing NaN and we don’t want runtime cost in a per-frame per-grid hot path.

S6.1 — Mid-tier mip overrides

When the picker returns Lod::Mid, Self::mid_mip_levels and Self::mid_mip_scan_dist (if Some) override the corresponding roxlap_core::opticast::OpticastSettings fields for that grid’s render. The intent: force coarser-mip rendering at Mid distance to recover performance, using the existing R4.5 multi-mip infrastructure with no new rasterizer code.

Semantics:

• mid_mip_levels = Some(n) — clamp OpticastSettings.mip_levels to n for this grid. n is then further clamped to [1, settings.mip_levels] at the call site.
• mid_mip_scan_dist = Some(d) — set OpticastSettings.mip_scan_dist to min(settings.mip_scan_dist, d). The renderer floors mip_scan_dist at 4 internally; smaller values transition to coarser mips closer to the camera, biasing the whole frame toward higher mips.
• Both None ⇒ Mid path renders identically to Near (graceful degrade — callers can opt into the Mid plumbing without committing to a mip override).
• crate::Grid::mip_levels_override continues to apply on top as a global per-grid cap regardless of tier (the ship anti-beam workaround is preserved at all LOD tiers).

Fields

r_near: f64

Maximum world-distance at which the grid renders at Lod::Near. Grids closer than this are full voxel.

r_mid: f64

Maximum world-distance at which the grid renders at Lod::Mid. Beyond r_mid the grid uses Lod::Far. Must satisfy r_mid >= r_near for monotonic tier dispatch; not enforced (an inverted pair just means the Lod::Mid band is empty).

mid_mip_levels: Option<u32>

S6.1 — OpticastSettings.mip_levels override applied only when the picker returns Lod::Mid. None ⇒ Mid uses the caller’s settings.mip_levels unchanged (graceful degrade to Near-equivalent behaviour). See struct doc for semantics.

mid_mip_scan_dist: Option<i32>

S6.1 — OpticastSettings.mip_scan_dist override applied only when the picker returns Lod::Mid. None ⇒ Mid uses the caller’s value unchanged. Smaller values bias the grid toward coarser mips earlier in the ray walk (floor of 4 inside the renderer).

Implementations

impl LodThresholds

pub const fn always_near() -> Self

Always-Near thresholds. Both distance fields set to f64::INFINITY; the picker can never enter the Mid/Far branches. Mid-tier mip overrides set to None (irrelevant since Mid is never selected). Use as the byte-identical default during the S6.0..S6.3 staged rollout.

pub fn from_radius(bounding_radius: f64) -> Self

Derived distance thresholds from the grid’s bounding-sphere radius (PORTING-SCENE.md § S6):

• r_near = bounding_radius — Near while the camera is inside the bounding sphere.
• r_mid = 10 * bounding_radius — Mid up to ~10× radius, Far beyond.
• mid_mip_levels / mid_mip_scan_dist ⇒ None (Mid degrades to Near; opt in via Self::from_radius_with_mid_mip).

A 0.0 (or negative) bounding radius collapses both thresholds to zero; the picker returns Lod::Far for any non-zero distance. That’s correct: an empty grid has no near range.

pub fn from_radius_with_mid_mip( bounding_radius: f64, mid_mip_levels: u32, mid_mip_scan_dist: i32, ) -> Self

Self::from_radius + an explicit Mid-tier mip override pair. Convenience for S6.1 consumers that want Mid LOD wired without hand-constructing the struct.

Typical values for a mip_levels = 4, mip_scan_dist = 128 world: mid_mip_levels = 4, mid_mip_scan_dist = 16. The reduced scan distance biases the Mid grid into coarser mips across the whole frame.

Trait Implementations

impl Clone for LodThresholds

fn clone(&self) -> LodThresholds

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LodThresholds

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for LodThresholds

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for LodThresholds

fn eq(&self, other: &LodThresholds) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for LodThresholds

impl StructuralPartialEq for LodThresholds