Coordinate Systems, Transforms, and Pivot Setup Guide

Coordinate frames control different operations

A transform is interpreted relative to a frame. World axes remain fixed for layout and global height checks; local axes follow the object and are useful for doors, wheels, and modular pieces; object coordinates describe points before the object transform is evaluated. A coordinate system mismatch often looks like a rotation problem even when the numeric channels are valid. Record the target up axis, forward axis, handedness, and unit scale before an interchange export.

Safe transform and pivot workflow

Duplicate or version the asset, reveal constraints and parenting, and inspect the transform matrix for negative or non-uniform scale. Confirm the desired pivot location and orientation, then test one representative rotation. Apply scale before operations that depend on physical dimensions, such as bevel width, cloth, or collision generation. Freeze channels only when the receiving workflow expects clean values. Export a test asset and compare its bounds, origin, orientation, and child placement in the destination.

Settings to inspect before freezing

Check translate, rotate, scale, rotation order, pivot position, pivot orientation, parent inverse matrix, and unit conversion. In a hierarchy, inspect both the selected node and its parent because a clean child can inherit a mirrored matrix. For animated assets, preserve joint orientation and bind pose. For procedural stacks, confirm whether modifiers evaluate before or after object scale. A displayed zero is not proof that the underlying matrix is safe.

Constraints and destructive boundaries

Applying transforms changes how geometry and downstream operations interpret the object matrix. It can alter bevels, arrays, simulations, normals, skinning, constraints, and instanced assets. Freezing an animated control can invalidate keyed values or retargeting assumptions. Never normalize a production hierarchy merely to make the channel box look tidy. If clean channels are mandatory, insert a parent offset group or rebuild the export node while leaving authored animation untouched.

Decision example: a modular door

A door arrives at world origin with a centered pivot, scale 100, and a rotated parent. The engine needs centimeters, Z-up conversion, and rotation around the hinge. First resolve units on a duplicate, then move the pivot to the hinge and align its local vertical axis. Apply scale while the mesh is unparented or compensating matrices are controlled. Reattach it, rotate it 90 degrees as a functional test, and verify that collision and bounds follow.

Failure diagnosis by symptom

An object rotating in an unexpected arc usually has the wrong pivot or an offset parent. Movement along surprising directions indicates local-axis orientation or parent rotation. A mirrored export often comes from negative scale or handedness conversion. Exploding children point to matrix baking without hierarchy compensation. A mesh that changes shading after transform application may need normals corrected. Compare matrix, bounds, and axis vectors before editing geometry; otherwise the original fault is hidden.

Evidence checklist for delivery

Capture the object at zero pose and at one test rotation. Record world position, local axis orientation, scale values, dimensions, unit settings, and hierarchy path. Show the pivot at the intended hinge, contact point, or center of mass. In the destination application, verify forward/up direction, bounding box, collision alignment, and one parent-child motion. Keep the exported file and import preset with the review so another artist can reproduce the result.

Related references and next step