I use Cycles renderer and nodes to output the image, normals and UVs at the same time. Here is what it looks light. Nodes

The preview in the RenderLayers node is what I expect (world positions).

However, when I press F12, in the Image file (Image0000.exr for the frame 0, etc), I get this : Viewer node output

instead of the expected result : The render result

(I think that in the first image the cubes are here, they're just the same colour as the plane).

The preview gives me the correct image but the output is wrong. And if I press the Animation button, the result is correct in the files 0000.exr, etc, but wrong in Image0000.exr, etc.

Am I missing something? Is there a problem in my nodes ?

Thank you for your help!

Thanks for the advice for using backdrop to debug, I figured out that it is the alpha node that was problematic : Incorrect result

Correct result

Could someone explain to me how this alpha node works ? Apparently I got it completely wrong.

  • $\begingroup$ Do you have a special need for exr? Many other people would use .png file format. Please show the blender image viewer used with the channel settings visible. If you have a special need for .exr please state simply your goal so we have a sense of what is correct or incorrect. $\endgroup$ Oct 9, 2014 at 17:04
  • 1
    $\begingroup$ @atomicbezierslinger The image being rendered is going to have colors brighter than 1. EXR supports such colors, but PNG does not (with png they will be clamped to 0-1). $\endgroup$
    – gandalf3
    Oct 9, 2014 at 17:06
  • $\begingroup$ You have two images. Is one a user view? Is one a render view? They seem to be from different camera angles. Perhaps only color is the relevant topic. I was trying to understand if you have shown the same frame in the images. $\endgroup$ Oct 9, 2014 at 17:10
  • $\begingroup$ @atomicbezierslinger They look like the same frame to me.. The OP said that both are rendered, one is from the file output node and one is not. $\endgroup$
    – gandalf3
    Oct 9, 2014 at 17:40
  • $\begingroup$ What happens if you enable backdrop in the compositor and connect some of the other nodes to a viewer node to see how they look? (Ctrl Shift LMB) $\endgroup$
    – gandalf3
    Oct 9, 2014 at 17:41

2 Answers 2


I'm not sure what you want the alpha over node to be doing there, but it's whats causing the white output.

Something as simple as this should work:

enter image description here

Example .blend


Change your image output to .PNG as inspection tool. Render the image and preview it the compositing node viewer, with backdrop selected, as an inspection tool.

Press 0 a few times to see Camera View and User View.

Choose the RGBA or RGB channels icon to view the image the correctly. Choosing Alpha would give a incorrect result.

Change the preview mode to be in Render.


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