I can not duplicate this. I just tried in P6 & 7. Sorry.
--- But I read this comment once about transparent backgrounds
12. Always render to a new window.
The render options screen gives you a choice between rendering to the current document window or rendering to a new window. Always choose the latter, even if you're rendering is the same size as the document window.
Why? Several reasons. First and most important, Poser has a feature called masking; it causes an alpha layer to be created in which the rendered character is presented in silhouette, and the rest of the background is masked off. This masking supports saving the render as a PNG file in which the figures appear against a transparent background (see next tip.) But when you render to the main document window, masking doesn't work properly; it's a bug in Poser 5. If you want proper masking, you need to render to a new window.
Rendering to a new window is also more convenient. When you render to the main window, it takes several seconds for the the screen to switch from render mode back to refresh mode; if you render in a new window, you can simply close that window and you're ready to continue.
Also, rendering to a new window makes it simpler to save your work, because you save the render separately from the scene file. You can do the same with a main window render by choosing export image; but it's less convenient.
13. Making backgrounds of renders transparent.
Poser creates a mask around the figures during rendering (see tip above.) This mask will cause the background to become transparent if you save the render as a PNG file. Note that the transparency is only in effect for certain graphic applications, including Photoshop; in some apps, such as Quicktime, the background is visible. I have no idea why.
A transparent background is very useful when compositing the render into a finished picture. It makes it easy to change the background behind the figure, for adding shadows and other revisions.
Note that the masking doesn't make the background 100% transparent-- there is an almost unnoticeable fringe of telltale pixels around the figure that are inherited from the background at render time. So it's best to render the figure with the background visible-- that way, the telltale fringe will match the background of the final picture.
