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I'm trying to replace the content of a box in a video, I have used the tracking system to match the movement of the video box with the interior of the one rendered in Blender, but I am running trough what seems a simple thing but I can't manage to get done.

I want the outside faces of the box to be invisible while hiding the inside of the box where the front wall of the box hides it, and the inside of the box to be rendered where visible. To do that I thought it would be as simple as making the face normals point to the inside of the box and giving a color only to the faces where normals are pointing to. But I can't manage to get that, am I going the wrong road? How can I achieve my goal?

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CYCLES RENDER

To give a texture only to the inside of the box you may use a Backfacing output of the Geometry node.
enter image description here

Unwrap your mesh and set the nodes as pictured below. Use a Backfacing output as a factor for two materials/textures. enter image description here

BLENDER RENDER

In Blender Internal you may also use the material nodes to achieve this effect. enter image description here

Unwrap your mesh and give it a new material. Check the Use Shader Nodes box. enter image description here

Now add two other materials- one for the inside and one for the outside of the box. enter image description here

In the Node Editor window set up the nodes as pictured below.
enter image description here

You may also add just one material and create two others within it using nodes. Unwrap your mesh and add a new material. Check the Use Shader Nodes box. enter image description here

Set up the material nodes as pictured below. enter image description here

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  • $\begingroup$ Thank you for your answer @Gonzou, couldn't it be achieved without nodes? I'm trying to stick to Blender Render instead of Cycles. $\endgroup$ – YoMismo Sep 28 '15 at 18:54
  • $\begingroup$ I'm afraid you'll have to use nodes in BI too to achieve this effect :). Check out my updated answer. $\endgroup$ – Paul Gonet Sep 28 '15 at 20:18
  • $\begingroup$ Great!!!! thank you very much, I'll let you see the final composite when I have it finished, it is just a box opening and smoke coming out of it (inside will be erased/replaced and smoke added with Blender's physics) :P $\endgroup$ – YoMismo Sep 28 '15 at 21:26
  • $\begingroup$ @YoMismo, I'm glad I helped :D. Waiting for the link with your finished project. Happy blending mate :). $\endgroup$ – Paul Gonet Sep 29 '15 at 0:44
  • $\begingroup$ I have finally finished the video. The inside of the box didn't have to be replaced since the smoke covered all the things that were inside and didn't have to be seen, so only a transparent material has been used to be able to use the box as a collision. Here is the link (don't laugh too much it is just a hobby for me & wife), skip to minute 3:27. youtube.com/watch?v=f8PcW7V9PSY $\endgroup$ – YoMismo Oct 11 '15 at 15:56

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