b3dDeltaYaw

Returns yaw angle needed for src_entity to face dest_entity (degrees, -180 to 180). Takes src_entity (source entity handle), dest_entity (destination entity handle). Returns delta yaw in degrees (Double), or 0.0 if either entity invalid. Validates both entities exist, calculates direction vector (dx, dz), computes target yaw angle atan2(dx, dz), subtracts current src yaw, normalizes to [-180, 180] range. Horizontal rotation angle to face target.

This function calculates yaw delta. Yaw angle: Y-axis rotation (horizontal plane), controls left/right facing direction, uses atan2(dx, dz) to get target angle in degrees. Delta calculation: targetYaw = atan2(dx, dz) * 180/PI, currentYaw = src.rotation.y, delta = targetYaw - currentYaw, normalized to shortest rotation ([-180, 180]). Normalization: while delta > 180 subtract 360, while delta < -180 add 360, ensures shortest rotation path (never rotate more than 180 degrees). Use cases: (1) AI facing (turn NPC to face player smoothly), (2) Turret tracking (rotate turret toward target), (3) Camera orbit (rotate camera around target), (4) Animation blending (blend between facing directions), (5) Smooth rotation (interpolate current yaw toward target yaw). Common pattern: delta=b3dDeltaYaw(entity, target), b3dTurnEntity(entity, 0, delta*0.1, 0) for smooth turning. Typical usage: calculate angle to target, apply fraction of delta each frame for smooth rotation, check if abs(delta) < 5 for "facing target" condition. Sign interpretation: positive delta means turn right (clockwise), negative delta means turn left (counter-clockwise), magnitude is degrees to turn. Smooth rotation: apply delta*rate instead of full delta for interpolated turning (rate=0.1 for slow turn, rate=1.0 for instant snap). Facing threshold: abs(delta) < threshold to check if roughly facing target (threshold=5-10 degrees for loose, 1-2 for precise). Performance: O(1) calculation (simple atan2 and subtraction, very fast), suitable for every frame per entity. Invalid entities: returns 0.0 if either handle invalid. Related: b3dDeltaPitch calculates vertical pitch angle to target, b3dTurnEntity applies rotation delta, b3dPointEntityAt instantly faces target (alternative to gradual turning).