reflection pass with alpha

Hello everyone. First of all sorry for my English.(translator)
I have a scene with an object on a floor, the object causes a reflection on the floor and I would like to extract the reflection in the floor to compose the object and reflection on a photograph that has another type of floor. How?
Any advice will be gratefully

First, you’ll need to put the floor plane on a separate Render Layer. Enable Reflection in the Passes section. Make the floor reflective and decrease the Gloss setting a little to match the type of surface in the photo. You probably don’t want the reflection to be perfectly sharp.

In the compositor, open a Render Layer for the reflection pass. Also open a Color:Mix node and set it to Soft Light. In the World settings, I set the Horizon color to a light gray. If this gray is too dark it will darken your entire scene. If it’s too light it will lighten it. Instead of repeatedly adjusting the Horizon color, you can use a Color Balance (or RGB Curves) node on the Reflection ouput and fine-tune the gray so that it doesn’t affect the rest of you image.

Use an Alpha Over node to composite the object into your photo.

In the picture below I used the Blam add on to align the camera to the table. Download Blam here…
[http://stuffmatic.github.io

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](http://stuffmatic.github.io/)

[Edited] Here’s a better version with AO pass set to Mix:Multiply. I also desaturated the blue color so it’s not so vivid.


Steve S

Thanks for the reply. This is in BI but in Cycles? sorry for not say what render engine

For cycles you can try to use Glossy Indirect pass. This gives you only the reflected objects that don’t have any emission components. The rest will be black.
This doesn’t have alpha, so you will need to play with blend types. I in most cases use “add” and set some low factor.

I tried it again in Cycles. I tried the Image output set to Soft Light and it gave the same result as in BI. I also tried the Glossy Indirect output set to Add, but it was a bit too bright. Combining both seems to give the best result.



Steve S