b3dGetEntityRadius

Returns entity sphere radius (for picking and collision detection). Takes entity (entity handle). Returns collision sphere radius (Double), or 0.5 if invalid entity handle. Reads entity->collisionRadius value set by b3dEntityRadius. Default radius is 0.5 for invalid handles.

This function retrieves collision sphere. Sphere radius: defines spherical bounding volume centered at entity position, used for sphere-sphere collision detection, used for sphere ray-cast picking (ray intersects sphere), complements AABB bounding box (box for frustum culling, sphere for simple collision). Use cases: (1) Collision detection (retrieve radius for sphere-sphere tests, calculate distance threshold), (2) Proximity checks (check if entities within combined radii), (3) Debug visualization (draw sphere at entity position with retrieved radius), (4) Dynamic radius (query radius before modifying, scale radius based on state), (5) LOD distance (retrieve radius for distance calculations). Common pattern: radius=b3dGetEntityRadius(entity), distance=b3dEntityDistance(entity1, entity2), if distance < radius1+radius2 then collision. Typical usage: retrieve radius for collision detection (check overlap), retrieve radius for debug drawing (visualize collision bounds). Default radius: returns 0.5 if invalid handle (moderate default size), entities created without b3dEntityRadius call likely have default radius (verify during testing). Sphere vs AABB: sphere retrieved by b3dGetEntityRadius, AABB has no getter (bounds set by b3dEntityBox, used internally), sphere easier to work with for distance-based logic. Radius units: world units matching entity position scale (radius=1.0 is 1 unit in world space), actual collision sphere affected by entity scale (effective radius = returned radius * entity scale). Performance: O(1) lookup (simple field access, no computation). Related: b3dEntityRadius sets collision sphere radius, b3dEntityBox sets AABB bounding box (alternative bounds), b3dEntityDistance calculates distance between entities (compare with combined radii).