FAQ/pEmitter to a path
From VFXPedia
In Fusion, pEmitter is always in 3D-space whether pRender is in 3D mode or not. So, it has 3D-coordinates (and it's great!).
The main differences between 2D and 3D-coordinates are:
Point of beginning (0;0) in 2D is at the left bottom corner of frame, but in 3D it is at center of frame.
In 3D space, scales of X and Y axes are equal (frame width = 1), but in 2D, scale of X depends on frame width and scale of Y depends on frame height, so the right top corner has coordinates X=1 and Y=1
To connect pEmitter to a motion path, You need:
1. RMB on pEmitter>Region>Translation>X Offset, Modify with..., Expression.
In the Expression connect "Point in 1" to the path an type p1x-0.5 in "Number out" tab
2. RMB on pEmitter>Region>Translation>Y Offset, Modify with..., Expression.
In the Expression connect "Point in 1" to the path an type (p1y-0.5)/<frame width>*<frame height>/<pixel aspect> in "Number out" tab (replace words in <> with numbers)
Here is an example: Connection_pEmitter_to_Path.comp
You can also connect any 3D-object to a 2D motion path using this method.
It can be done by means of Simple Expressions:
1. RMB on pEmitter>Region>Translation>X Offset, Expression.
Enter to the expression field: <Tool with Path>.<Parameter Modified with Path>.X-0.5
For example, Merge1.Center.X-0.5
2. RMB on pEmitter>Region>Translation>Y Offset, Expression.
Enter to the expression field: (<Tool with Path>.<Parameter Modified with Path>.Y-0.5)/<frame width>*<frame height>/<pixel aspect>
For example, (Merge1.Center.Y-0.5)/720*576/1.066667
