Use part of an image sequence as specular map I'm using Blenders plane track feature to replace a sign with an image sequence.

Now I want to add a little bit of realism to the scene so I 3D tracked it too and added a ground plane to catch the reflections of the screen. Of course I want the reflections to blend in better.

I'd like to use the ground of the background image sequence as a specular map. The asphalt is showing through and those parts should not be as reflective as the snow.

Is there some smart way to project the ground part of the background on to the plane?



Here's the background and the replaced sign I want to shine somewhat on to the snow.
Within Blender you can create a mask in the Image Editor, and then go into the compositor To Get This less saturated and rendered out with the Mask applied, then saved out as a Specular Map for this reason. I will play around with it, and append this answer with some screenshots/blend files/step-by-step instructions/etc...

Before I go much further, is this what you are asking for?: