I know that there's information in the forum about this topic but this is kind of different. The last days i have surfed all the tutorials at the cow and other sites covering that subject and none of them offers a solution to my problem.
The thing is that i am composing the typic slideshow in coverflow style. With the placeholder reflecting into the floor and also casting shadows. All the tutorials approach this type of compo without a floor layer. Only a BG layer with smooth gradient to simulate it. This way you can duplicate the placeholder, mirror it, add some wipe and blur and there you have your reflection.
But what i wanted to do is the same effect without sacrificing the floor 3d shadows. As AE doesn't have raytracing in its render engine it can't project a real reflection and you also have to simulate it, but again, when you put a floor layer it covers that reflection. Otherwise said; you have to choose between 3d reflections or 3d shadows on the floor.
In Andrew Kramer cow's tutorial he uses an adjustment layer to force render the reflection layer before the floor. So it can be seen although the floor is covering it. But this way "erases" the 3d shadows and light transmissions of the placeholder. And it is impossible for me to simulate them to be so real. Not to be said that it would be very slooooooooow to render due to the amount of layers and effects.
Is there a way to get 3d floor reflections, 3d floor shadows and light projections at the same time?
Think I know what you are trying to accomplish, I've run into the same issues. Solution I came up with isn't going to render quickly but works.
Under the adjument layer, you have your reflection stuff. What you need to do is make copies of whatever you want to cast shadows and put that under the adjument layer also. I don't think you will need to make a copy of the light. Under the material properties of these things, just change them to "shadow only"
Kind of cumbersome work around, but it does the trick.