<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <script src="../../list.js"></script> <script src="../../page.js"></script> <link type="text/css" rel="stylesheet" href="../../page.css" /> </head> <body> <h1>[name]</h1> <p> Three.js uses *matrices* to encode 3D transformations---translations (position), rotations, and scaling. Every instance of [page:Object3D] has a [page:Object3D.matrix matrix] which stores that object's position, rotation, and scale. This page describes how to update an object's transformation. </p> <h2>Convenience properties and *matrixAutoUpdate*</h2> There are two ways to update an object's transformation: <ol> <li> Modify the object's *position*, *quaternion*, and *scale* properties, then ask Three.js to recompute the object's matrix from these properties: <code> object.position = start_position; object.quaternion = quaternion; object.updateMatrix(); </code> Calling the *updateMatrix* method forces the object's matrix to be recomputed from *position*, *quaternion*, and *scale*. You can also set <code> object.matrixAutoUpdate = true; </code> in lieu of calling *updateMatrix*. This will force the matrix to be recomputed every frame; for static objects, you should therefore set <code> object.matrixAutoUpdate = false; </code> </li> <li> Modify the object's matrix directly. The [page:Matrix4] class has various methods for modifying the matrix: <code> object.matrix.setRotationFromQuaternion(quaternion); object.matrix.setPosition(start_position); object.matrixAutoUpdate = false; </code> Note that *matrixAutoUpdate* <emph>must</emph> be set to *false* in this case, and you should make sure <emph>not</emph> to call *updateMatrix*. Calling *updateMatrix* will clobber the manual changes made to the matrix, recalculating the matrix from *position*, *scale*, and so on. </li> </ol> <h2>Object and world matrices</h2> <p> An object's [page:Object3D.matrix matrix] stores the object's transformation <emph>relative</emph> to the object's [page:Object3D.parent parent]; to get the object's transformation in <emph>world</emph> coordinates, you must access the object's [page:Object3D.matrixWorld]. </p> <p> When either the parent or the child object's transformation changes, you can request that the child object's [page:Object3D.matrixWorld matrixWorld] be updated by calling [page:Object3D.updateMatrixWorld updateMatrixWorld](). </p> <h2>Rotation and Quaternion</h2> <p> Three.js provides two ways of representing 3D rotations: [page:Euler Euler angles] and [page:Quaternion Quaternions], as well as methods for converting between the two. Euler angles are subject to a problem called "gimbal lock," where certain configurations can lose a degree of freedom (preventing the object from being rotated about one axis). For this reason, object rotations are <emph>always</emph> stored in the object's [page:Object3D.quaternion quaternion]. </p> <p> Previous versions of the library included a *useQuaternion* property which, when set to false, would cause the object's [page:Object3D.matrix matrix] to be calculated from an Euler angle. This practice is deprecated---instead, you should use the [page:Object3D.setRotationFromEuler setRotationFromEuler] method, which will update the quaternion. </p> </body> </html>