b3dCreatePivot

Creates an invisible pivot entity for grouping and transforming child entities. Takes no parameters. Returns pivot entity handle. Increments g_nextEntityHandle. Initializes Entity3D with type ENTITY_PIVOT. Sets default position (0,0,0), rotation (0,0,0), scale (1,1,1). Sets worldMatrixDirty = true for matrix recalculation. Sets gpuTransformIndex = -1 (no GPU upload needed). Sets parent = nullptr (no parent initially). Sets visible = true, renderOrder = 0 (defaults). Sets mesh = nullptr (pivots have no visual mesh). Stores in g_entities map. Returns handle, never fails. Pivots are organizational nodes in scene hierarchy - they don't render but affect child transforms. Use b3dSetParent to attach entities to pivot. Moving/rotating pivot moves/rotates all children relative to pivot's transform. Essential for articulated models (robot arm: shoulder pivot -> upper arm -> elbow pivot -> forearm), complex animations, grouped movement.

This function creates transform-only entity for hierarchy management. Pivot transforms multiply down hierarchy: childWorldMatrix = parentWorldMatrix * childLocalMatrix. Common use cases: (1) Character rig - pelvis pivot with leg/spine children, (2) Vehicle turret - chassis pivot with turret child, (3) Solar system - sun pivot with planet children, planet pivots with moon children, (4) Door hinge - door frame pivot with door child rotates around pivot point, (5) Camera rig - boom pivot for orbital camera. Pivots support full transform operations: b3dSetPosition, b3dSetRotation, b3dSetScale, b3dMoveEntity, b3dTurnEntity. Pivots can parent other pivots for multi-level hierarchies. World matrix calculated recursively during rendering. Visible flag inherited by children unless overridden. Collision/physics can attach to pivots. Pivots have no performance cost (zero vertices/triangles). Use liberally for organization. Alternative: parent entities directly to mesh entities, but pivots clearer for pure transform nodes.