b3dEntityDistance

Returns Euclidean distance between two entities (0.0 if either invalid). Takes src_entity (source entity handle), dest_entity (destination entity handle). Returns distance in world units (Double), or 0.0 if either entity invalid. Validates both entities exist, calculates delta position (dx, dy, dz), returns sqrt(dx*dx + dy*dy + dz*dz). Simple 3D distance calculation.

This function calculates Euclidean distance. Distance formula: distance = sqrt((x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2), standard 3D Pythagorean theorem. Use cases: (1) Range checks (is enemy within attack range?), (2) Proximity triggers (activate when player near object), (3) LOD selection (use low detail for distant objects), (4) AI behavior (chase if close, flee if too close), (5) Sound attenuation (volume based on distance). Common patterns: distance check if b3dEntityDistance(player, enemy) < 10 then attack, proximity trigger if b3dEntityDistance(player, door) < 2 then open door. Typical usage: check distance before expensive operations (AI, visibility), use for range-based game logic (weapons, triggers, audio). Performance: O(1) calculation (simple sqrt and subtraction, very fast), suitable for frequent calls. Zero distance: entities at exact same position return 0.0 (use for collision detection, compare with combined radii). Invalid entities: returns 0.0 if either handle invalid (check entity exists before relying on distance). Distance squared: this function returns actual distance (includes sqrt), for distance comparisons without sqrt use manual calculation (dx*dx + dy*dy + dz*dz < range*range) to avoid sqrt cost. Related: b3dEntityVisible checks line-of-sight between entities (uses distance for ray length), b3dGetEntityRadius retrieves collision radius (compare distance with combined radii for collision), b3dDeltaYaw/Pitch calculate angles to face target.