View Full Version : Expression help needed

01-11-2006, 02:43 PM
I'm trying to animate a scene where the client requires the shot to pan from an orthographic side view to an overhead orthographic view, but during the transition needs to show perspective.

I've been able to find some settings (thanks to the replies from my last post) that work for getting an ortho shot, but getting in and out of perspective and keeping the camera on the object is a real nightmare!

The extremes are silly so getting a nice smooth transition is problematic to say the least.

I was wondering if some kind of expression linked to the camera's FOV made do the trick, but I'm not good with those, so any help or alternate suggestions is much appreciated!

01-11-2006, 10:48 PM
If you don't dig expressions you should do yourself a favor and familiarize yourself with Cycler.

I'm assuming you are moving the camera backwards in z and zooming in really hard to achieve the transition from perspective to something orthographic-like.

So create an animation for the camera where on frame 0 it's in "perspective mode", ie z=0 and zoom=3.2, and on frame 10 it's in "ortho mode", ie something like z=1km and zoom=500. Play with the envelopes so you get a a somewhat nice smooth transition over those 10 frames. Now add a null that will act as a controller for Cycler, call it "Cam_Ctrl" or whatever. Now start by adding Cycler to the Cameras z channel and set Cam_Ctrl.Position.Y to be it's control channel and set Controller High and Low Value to be 0 and 1, and Cycle Start and End Frame to 0 and 10 to match the frames above. Copy the modifier and paste it into the cameras zoom channel aswell. Now when you animate the control null on Y you'll transition between a perspective and orthographic mode. Since this setup inevitably will move the camera far of in the distance you should parent the camera to a null and move/rotate that null whenever you want to reposition the camera. See attached scene. I added a slider aswell just for the visual aspect of it.

Expressions as an alternate route shouldn't be very hard either but it will be tougher to get a nice transition since you have no envelopes to play with. Achieveing a smooth transition would require more tought. For the simplest possible setup just attach 'Camera_Ctrl.Position.Y * -1000' to the cameras Z channel so when the control null is at 1 meters in Y the camera will be at -1km in Z. Simularly attach 'Camera_Ctrl.Position.Y * 500' to the cameras zoom channel so it will be at 500 when the control null is at 1 meters in Y.

01-12-2006, 02:30 AM
Thanks for the advice and scene file - its much appreciated! :thumbsup: