Make a few fixes to the shadow rendering output on transparent background

Jacob G 8 years ago updated 6 years ago 0
A few issues here:

If you render an image with ambient lighting and a background image, the multiplication of the lighting gets applied to the floor on top of the background image. This seems strange to me.

However, if you remove the background image in order to just render the object with transparent drop shadows, the shadows on the floor disappear, and any ambient lighting settings appear as png haze.

What is strange, is that skylight effect shading still works - just not shadows cast from light objects. In other words, I was trying a test comp with this NASA model... when I included the background image in the render, hotspots appeared under the light object on the floor, multiplying brightness against the bricks. Dropping ambient light to better match the background resulted in vignetting... and this vignetting did not go away once the background image was removed.

As a result, the comp has slight skylighting shadows, and correct lighting from the light objects, but the shadows cast on the floor were not rendered - and the comp fails unless I go in and fab the shadow myself.

Perhaps you can see the end result... http://sphotos-b.xx.fbcdn.net/hphotos-ash3/154623_605168251292_764116738_n.jpg