The Revit Kid demonstrated today that PNG files exported from a Revit render have no background.

In the spirit of one-up-man-ship, I recommend that you use TIF if you want to keep the background, but quickly separate it from the model elements.  When you export as TIF, you get a bonus Alpha channel that you can use to create a selection area and move the background to a new layer.

In simple terms:

  1. Export Revit render as TIF
  2. Open in Photoshop
  3. Isolate the Alpha channel
  4. Use Magic Wand to pick everything that is ‘white’
  5. Turn the color channels back on
  6. Invert the Selection
  7. Convert the background to a true layer
  8. Edit – Cut
  9. New Layer
  10. Edit – Paste
  11. Done!

Now you can manipulate the model elements and the background separately.

Here is a video:

 
Of course, you can also do this easily by:

  1. Doing two separate renders, 
  2. one of them with Model Elements turned off (which will just show the background) – Export this to any format except PNG
  3. and one of them with Model Elements on (export this to PNG)
  4. Copy and paste these two images to separate layers in Photoshop

 The TIF method is probably quicker and easier in most instances.

Here is a link to the aforementioned PNG post:
The Revit Kid.com!: Revit Tip – Export Rendered Images Without a Background

There are some basic rules of Priority, that all compound structures follow, when joining together.

1) The higher priority layers always take precedent. For example, a Priority 1 layer will barge it’s way through lower priority layers in order to join up to another Priority 1 layer.

2) Lower priority layers cannot cut through higher priority layers, during the “clean up process”- they are just stopped by them.

3) The exception to both of the above are layers that fall within the Core boundaries. A priority 2 layer “within the core boundaries” will override a priority 1 later” that is situated “outside of the core boundary”.

Tip via
Walls: Applying Functions to Compound Layers:

Image from Revit Zone