MaterialXView capture dimensions not set properly

[kwokcb]

Issue

It seems if you set the screen dimensions on MaterialXView for interactive and command line they are sometimes set properly.
It seems that if the size is not too small (like 64) and not too large(1024) then it will work.

Example

This never seems to work:

MaterialXView  --screenWidth 1024 --screenHeight 1024

versus

MaterialXView  --screenWidth 1024 --screenHeight 1024 --captureFileName x.png

512 x 512 works, but 64 x 64 does not.

From brief testing it seems the size used to capture with is fixed and if the screen capture size somehow fits with this size it will capture properly. Otherwise the screen size is ignored.

This was only tested on Windows at SHA: e0d72e7