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Edit: Please looks at the image below. It is a better view

enter image description here

enter image description here

As shown in my render above, you can see the exhaust of the ship somehow protruding through the engines. The exhaust and the ship are separate render layers with the ship being above the exhaust. I have composited them with the Add node with the ship above the exhaust. It's not the ship's material as it not transparent and when they are on the same render layer it looks fine. My render layer properties look like this:

enter image description here

How can I make the exhaust go behind the ship, what am I doing wrong?

Edit:

enter image description here

This is my compositor with the Alpha over node. I just added a few adjustments to the exhaust, but the problem persists.

todaywiththeCJB
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2 Answers2

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Use "Alpha over" instead of "Add" node

Assuming that you are in a situation with a bright light sources behind your object like in the example below:

enter image description here

The use of an Color Add Node would sum the pixel colors from the two render layers, while what you probably want is to override the pixel color information basing on which layer is in front of you.

In this and your case, as both the layer of my light and your exaust are almost white, we can't see the "adding" because the are both almost full white, so what exceed the full white (RGB=1,1,1) is being clamped to 1.

enter image description here

Here's an exampe with a light source whose strength is 0.1, The addition is more visible now.

enter image description here

I would suggest to use the Alpha over node instead, which put the second imput image imput upon the first imput image taking alpha channel in account.

enter image description here

Remember that the second imput socket of the Alpha over node is the images that will be put above the source image (which is connected from the firts imput socket). So in your case, the source image must be the Exaust, and the second the Ship.

From the Blender reference manual's page about Alpha over node:

Use this node to layer images on top of one another. This node takes two images as input, combines them by a factor, and outputs the image. Connect the Background image to the top input, and the foreground image to the lower input.

Carlo
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  • This surprisingly didn't work. I'll keep working on it and thanks for your help! – todaywiththeCJB Oct 19 '15 at 20:01
  • He he! Must be something else. If you want more help, I would suggest to show your compositing setup ( you can bypass the two-image-limit for new users in the question by merging two images in one), or maybe ulpoad your blendfile to http://blend-exchange.giantcowfilms.com/ for a deep inspection. No issue can overcome a deep inspection! – Carlo Oct 19 '15 at 20:08
  • I added a pic of my composite as an answer above. – todaywiththeCJB Oct 20 '15 at 12:00
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    Ok, I have put that in your question field, to make it more visible. I would suggest to delete your "fake answer" now. – Carlo Oct 20 '15 at 12:47
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I fixed it by putting the exhaust above the ship. Weirdly it worked!

enter image description here

todaywiththeCJB
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