Hello Thomas, In review,
The Face-me objects contain two identical polygons, one that always faces the camera (texture mapped polygon), and one that always faces the sun (non visible polygon which creates the shadow). In the Sketchup renderer, the polygon which faces the camera does not accept shadows.
This technology has been used in games for many years. It allows the real time renderer the ability to display high levels of detail without having to create 3d polygonal objects (trees, bushes etc.) which slow down the renderer.
It is not perfect. But in many cases it works exceedingly well.
All of the trees, bushes and people in the image above were done with face-me objects. At the time this was done, about 7 years ago, this was running at about 10 frames per second in Sketchup. The only thing that is post processed in this image is the water in the foreground. Everything else is straight out of Sketchup. (including the sky and the aerial perspective, known as fog.)
I have thought for a long time that the fact that Face-me objects do not except shadows has been a limitation, but I am willing to live with this because the graphic horsepower that face-me objects provide is too good to be true.
As the Sketchup community starts to look at outside renderers such as Enscape, Lumion, Unreal etc. It is probably a good idea to look at the shadowing problem more closely.
In an ideal world! one could set the state of surfaces as to whether they could receive a shadow, or not,
without slowing down the real time renderer. At this point I believe most sketchup users simply want the shadow polygon to not self shadow the Face-me object (the textured polygon), but still cast a shadow on the surrounding world.
If this is simply done with emissivity, then that would be a quick solution! A very welcome solution, I might add.
However, I think the problem could be taken a step further, Where Face-me objects COULD receive shadows from the surrounding world, But NOT from it’s own shadow polygon. (and of course also still shadow the surrounding world)
I know that there is a tendency to think that a real time renderer should be all about 3d objects ONLY.
In the case of foreground specimen trees , it is desirable to have more sophisticated shadow interaction, including self shadowing. This can only be done with high quality 3d polygonal models. But for mid ground and background objects, in many cases, a flat “billboard” is sufficient.
In my view, Face-me objects are here to stay, enabling the artist incredible speed and exacting art direction in a light weight rendering technique.
Thank you for looking into this, it really means allot to the Sketchup community, who has invested deeply into entire libraries of face me objects for many years! (in my case over a decade)