Complicated layering setup - how to render objects infront even though they are behind others?

[MANUEL_MOUSIOL]

Hi,
since days I am trying to figure out a way on how to achieve a rather complicated setup. We are trying to slim down our rendering and comping process. Let me explain the setup:

• Currently we render out the upper part of a car and use a grey mask of it in half-opacity to represent that part.
• The photoreal rendering of the chassis of the car is sitting ON TOP of the main part (since the chassis is the main product here)
• On top of everything come white lines that visualise the different parts of the car like windows or bumper or sidemirror etc.
• BEHIND everything come lines of the car that are visible behind the car (which is half transparent). They appear as light grey lines since the grey-solid of the main part sits on top of that.

Right now we are rendering out 4 images and comping them together, which is a bit too complicated for my taste. I´d rather have one rendering.


The problems:

• The main part, which becomes a grey half-transparent solid, has to sit BEHIND the chassis, while obviously in fact it sits INFRONT (or rather on top) of it. We could maybe solve this with a double sided material with the front material being empty, the vray way of having a backface cull. But the main car will have faces that sit infront of each other probably and the backface cull might not always work. We basically just need the car to always be rendered behind the chassis.
• Lines that are behind the main part of the car have to be half-transparent or grey, but obviously if perspective changes, the parts behind might become the parts infront. I would like to automate that. I was thinking of an override material, making the main solid part of the car refract (IOR 1) and making the lines appear differently through refraction. this would probably mean that the lines, which are currently achieved through sweeping lines in 3ds max, would have to sit a little bit outside of the cars main part.

You see, its complicated and I wonder if anybody really understand what I am talking about haha
so if you have any questions so you can point me into the right direction to simplify this process, I would be very happy to answer them

Cheers,
Manuel

[vladimir_krastev]

Hi I am afraid it is extremely difficult to understand exactly what is going on. Could you upload an image of your final result that you achieved and want to optimize?