Parameters
- bmpsize
 - the size of the resulting bitmap, rounded up to the nearest integer
 - dpi
 - bitmap resolution
 - viewpos
 - a 
Pointin model coordinates for the top-left corner of the area to be rendered - scale
 - a value of 1.0 is normal; the value must be a positive number. Smaller values produce smaller-looking parts.
 - act
 - an 
Actiontaking theBitmapSourceto be performed later; this may be null 
Return Value
a 
BitmapSource