Grass Vanishes When Camera Selected - Appears WHen Camera Deleted

[Argyll46]

I have a simple scene with grass filling a rectangle and it renders fine. I create a camera and orient it with the target on the far side of the rectangle. I select the Camera and up to this point everything is fine. If I now select the camera from the toolbar dropdown list, all of the grass vanishes and the rendering is blank. If I delete the camera everything is back to normal. What's going on?

[iToo]

By default Forest hides all the items which are not visible from the current camera's view. You can modify this behaviour in the "Camera" rollout ("Limit to visibility" parameter).

Probably the rendering is black because you are rendering a Perspective, not a camera. So Forest is using the clipping of the latest camera selected.

[Argyll46]

No you misunderstand what I'm saying. As soon as I switch to the camera view all the grass vanishes - it doesn't render (the scene isn't black) and can no longer be selected. Until then rendering a perspective view worked fine. If I change the limit visibility to on prior to selecting the cameras view, I can see it works as it should with grass inside the cone of visibility appearing or being hidden according to how I change the Expand parameter. Once the grass vanishes, the grass only reappears if the camera is deleted.
Screen capture attached showing what's happening.

[iToo]

I'm not sure what may be the problem. Please, post the scene to check it.

[Argyll46]

I've attached the file for you to have a look at.
I've tried replicating what's happening, but everything in other files appears to work as expected, so I'm not sure what's causing this problem - it will crash 3ds max 2012 if you play around with it after you've viewed the camera in a viewport and gone back to perspective mode. You'll notice that once the grass vanishes a tick is left behind. You cannot select this unless you select everything in the scene then do a ctrl + I to invert the selection. It's shortly after I do that when 3ds max crashes.

[iToo]

The problem is in Forest004 (the grass clump). It has the camera clipping enabled, so it doesn't generate any geometry from the Camera001 view. Since this object is used as Custom Object for Forest005, this was not generating any items either.

Turning off "Auto assign to active view" and clearing the camera in Forest004 should solve the problem.

[Argyll46]

Thanks! That did the trick. That's quite a trap to fall into when there are a number of items in the reference object (Forest004 in this case). Maybe that option could be checked in the software (more work for Itoo  ) and automatically ticked off when a series of items are used in a reference object? Anyway, thanks for the leg up with this one.

[iToo]

I add your suggestion to the wishlist.