World Position Pass is a depth matte used for obscuring other layers so they appear to be intersecting with an Element object or scene. This can be turned on at Output/Show World Position. It is similiar to a Z-Depth matte but it stays in the same position as the camera moves.
Create your Element object and add a camera to easily manuever around the scene.
Create a new after effects layer or import a piece of footage and flip the 3d switch for the layer. You will see that the Element layer and AE layer exist in seperate 3d spaces layered on top of each other.
Duplicate your Element layer and put it above your 3d footage. In the duplicate Element layer go to Output/Show and change Composite to World Position.
On the AE layer or imported footage layer change the Track Matte mode (TrkMat) to Luma Inverted. If you don't see the Track Matte options hit the Toggle Switches/Modes button at the bottom of After Effects to cycle through the layouts till you see it. Now you can see the Layer intersecting with the Element object and you can adjust the World Position settings to adjust the look.
If you need to move the Camera behind the object you can check the Invert from Back button so that the matte works from behind as well.
Element v1.6 New Features Video (Check out at around the 6 minute mark)
• Group Nulls
• Scene Relinking
• World Position Passl
• View More Features
Matte will show the black and white pass, while the Color option outputs the exact XYZ coordinates (project needs to be 32bpc).
Moves the Matte on the X and Y axis, usually changes can be noted with this value when the matte is rotated.
Moves the Matte on the Z axis, typically closer or farther from the Camera.
Rotate the matte on the X axis
Rotate the matte on the Y axis
Increase or decrease the size of the matte in Z space
Soften or Sharpen the edge of the matte
Lessen jagged edges of the matte
Lets you Soften each side of the matte
Brighten or Darken the matte, most noticeable in grey areas.
Reveses matte from the back side.
Matte always is toward camera
Matte is black from the back
Control when the Matte becomes invisible.
Soften the change from front of matte to the back black matte
Make background transparent
Creates a null object that controls the position and rotation of the matte.
Mixing Layers & Particles with Element 3D
You can duplicate your Element layer, set one to World Position, and use that layer as a track matte for a layer or particle effect that you want to integrate in the same 3d space.