Ground reflection without ground


is there a way to get a “keyed reflection” like the one on this image in Blender?

I guess the Raytraced Reflection Pass is the key to success, but I didn’t find a way to separate the reflection from the reflecting ground.

Any ideas are appreciated.



What may work is to create a plane and add a material.
Set the material to shadow only.
Then turn on the raymirror to 100%.
Now the reflection will only appear in the shadow area, effectively becoming a mask for the reflection.
The only problem with this is that you have to align the light source to the camera (perhaps parent it after it is aligned). Then your reflection will always fall in the angle of the camera and the alpha will be preserved.

Ideally, there needs tobe a “Reflection Only” button just like the “Sahdow Only” button.

Good luck!

You could use compositing nodes. In the render layers tab, enable “Refl” at the bottom. Now you can extract just the reflections from the rendered image.

Atom: Yes, a “ReflectionOnly” button would be great :D.

BlendRoid: The Raytraced Reflection Pass was the approach I already tried, but I just couldn’t get decent results.

After some further testing, I’m using this node setup now:

This is the result it shows in Blender’s Viewer Node using “Draws image with alpha” - it’s not what I need:

But… surprise: this is how the saved image looks opened in an image software:

Strange, isn’t it? I think the “Draws image with alpha” button just misled me all the time. I doesn’t seem to work properly.

However, I found a way to get what I want - but I guess there are better ways…



I am trying to setup my nodes like you have. I’m not sure how, is there any way you could post a BLEND file somewhere? This seems like a useful setup.

Does it hold up against AO renderings?

Atom: AO should be no problem, I just didn’t add it in my example. You’ll find my test file >here. Have fun…