How to remove gray background behind billboard trees when rendering?

Issue description

When rendering your project with 2D tree objects you notice gray rectangular backgrounds appearing behind the tree sprites instead of transparent areas around the foliage.

Solution

This problem occurs because the Color Mapping effect in the rendering settings is affecting the background areas of tree sprite objects. By default Color Mapping processes all elements in the render including transparent backgrounds which can cause unwanted coloration.

To resolve this problem you need to disable the Affect Background option in the Color Mapping settings:

1. Open Document > Creative Imaging > PhotoRendering Settings
2. Enable Detailed Settings in the PhotoRendering Settings palette
3. Navigate to the Effects tab in the detailed view
4. Locate and expand the Color Mapping section

5. Enable the Affect Background option
   

    

    

   

   
    

6. Render your image again to see the corrected result
   

Alternative Solution: Use Physical Renderer

If the above method does not completely resolve the issue you can switch to using the Physical Renderer which handles transparent tree objects more effectively:

1. In the PhotoRendering Settings go to Detailed Settings
2. Enable Use Physical Render in the rendering options.
   
3. This setting provides better transparency handling for bitmap tree objects

Additional Information:

For best results when rendering tree objects ensure you are using appropriate tree library elements that include proper alpha channel information for transparency. Some older tree objects may require updating to newer versions that better support transparent backgrounds.