Ok now we need to put the main render on this layer, but we only need the car not the environment. So let's use the third image to mask the image over the background layer. To do the mask effect, first drag and drop the main image on the background layer and then click on the Add Layer Mask parameter under the Layers panel. Then Alt + Click the second layer slot and just copy and paste the mask image to get the result needed. Then select the layer and choose Darken in the Blending Mode list. As I said you may get different results depending on different color types, shadow types and other factors so you may want to try other modes, but the process is the same. After applying the changes on the second layer we should have the result shown in Fig.19.



So far we have brought the missing smooth shadows back, but it's not yet the result we are looking for. So duplicate the layer with different Blending Modes and different Opacity values to get a better result. The new layers have various blending modes like Color Dodge, Lighter Color, Soft Light and Hard Light to get a clearer image. Take a look at this image to get the idea and take note of the blending modes and their opacity values (Fig.20).


So that was the studio render of our Pontiac. Remember that we chose this method to get a good render with the least time, but if you want to get the same result directly from mental ray with no post processing you can let the engine process and create the GI. To do so, using a Skylight would be good idea. Create a Skylight and activate Global Illumination and Final Gather in the mental ray settings. Test your renders with the lowest sampling quality and try out different lighting setups to get the result desired. Also using a HDRI map in the environment background will help your image to get more realistic reflections and quality.

And here's the finished image (Fig.21).