Position

In order to fully understand all the ways to locate a mesh in the scene we need to know about frames of reference. When creating a world in a scene we are using a frame of reference in the World Space. In Babylon.js world space there are two horizontal axes, x and z, and a vertical y axis in a left handed system. Each mesh in the scene also has its own Local Space. Meshes are created with their local space origin at the world space origin and with their local space x, y and z axes aligned with the x, y and z axes of the world space.

Locate a mesh (rotation doesn’t matter)

Consider a mesh with its local origin in world space at (-1, 2, 1), that is mesh.position is at (-1, 2, 1); Babylon.js has a number of ways to reset the location a mesh. These are listed in the code below. The comments show the location of the local origin of the mesh in world space after each way has been applied. The following are true for a mesh whether it has been rotated or not.

mesh.position = new Vector3(2, 3, 4);//(2, 3, 4)
mesh.position.addInPlace(new Vector3(2, 3, 4)); //(-1 + 2, 2 + 3, 1 + 4) = (1, 5, 5)
mesh.translate(new BABYLON.Vector3(2, 3, 4), 1, BABYLON.Space.WORLD); //(-1 + 2, 2 + 3, 1 + 4) = (1, 5, 5)

mesh.position.x = 2; //(2, 2, 1)
mesh.position.y = 3; //(2, 3, 1)
mesh.position.z = 4; //(2, 3, 4)

mesh.position.x += 2; //(-1 + 2, 2, 1) = (1, 2, 1)
mesh.position.y += 3; //(1, 2 + 3, 1) = (1, 5, 1)
mesh.position.z += 4; //(1, 5, 1 + 4) = (1, 5, 5)

Locate a mesh (rotation matters)

In Babylon.js, a mesh’s position is often calculated relative to its current rotation. When you apply transformations (such as moving the mesh forward or backward), the direction it moves in depends on how it is oriented. For example, if a mesh has been rotated to face a certain direction, moving it “forward” might no longer mean along the world’s Z-axis (which is usually forward in Babylon.js) but rather in the direction the mesh is facing due to its rotation. Thus, you can’t accurately calculate or predict a mesh’s new position from these methods without knowing how the mesh is rotated. If you move a mesh in local space (relative to its own orientation), its position will be influenced by both its translation and its rotation. For example:

• if a mesh is not rotated, moving it along the Z-axis would move it forward in the scene.
• if the mesh is rotated, the same movement along the Z-axis might move it in an entirely different direction based on its current orientation.

Using the following methods the resulting position depends on the orientation of the mesh. It is not possible to give a resulting position without knowing the rotation of the mesh.

mesh.translate(new BABYLON.Vector3(2, 3, 4), 1, BABYLON.Space.LOCAL);
mesh.setPositionWithLocalVector(new BABYLON.Vector3(2, 3, 4));
mesh.locallyTranslate(new BABYLON.Vector3(2, 3. 4));

Learn More

For a comprehensive understanding, please refer to Babylon.js documentation: https://doc.babylonjs.com/features/featuresDeepDive/mesh/transforms/center_origin/position/.