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sugarandfat
08-25-2007, 02:44 PM
Hi all. I've got a contract requiring a highly photoreal 3d car (model provided) into a photo background.

Are there any good tutorials out there on this? Dealing with car specific shaders, reflective occlussion passes, all that jazz.
I'll be working in Maya and MentalRay.

cheers.

Sphere♥
08-26-2007, 03:22 AM
Like with most metals, glasses and plastics, the most important part is to have a realistic environment for your car to reflect. If you are using a photo background you'll probably want an HDRI or spherical environment image that matches as close as possible to get the most realistic reflections bouncing off the car.

For example: given a simple, non-photorealistic poly car, with just it's wireframe as texture (AO render):
http://img505.imageshack.us/img505/6030/80montgm0.jpg

Simply by making it reflective, dropping it into an HDRI environment with a useBackground floor to catch shadows and a FG preview render we get:
http://img505.imageshack.us/img505/5606/80monthdrioo3.jpg

This low poly car with no texturing at all is not photorealistic but just reflectivity and an HDRI environment take it a long way.

Grgeon
08-26-2007, 06:49 AM
Looks great!

-George

sugarandfat
08-26-2007, 11:47 AM
I'm going to be using the car paint shader which comes with mentalray, I've used it a little before and it gives really nice results.

I guess what Im asking is what passes should I be rendering and how should I be comping them to get the best results. ie beuty, reflection, gi, ambient occlusion, reflective occlusion, etc, and what effects to apply to each if any. (ie flaring the specular)

JasonA
08-26-2007, 04:26 PM
Depends on how much "tweaking" you want to do in post and how much time you have (each pass takes time and the sum of the passes does not nessesarily equal the time taken for a beauty render). If you get the look you need in the beauty render, that might be all you need (not much flexibility though).

If you decide to go with passes, you could keep it simple and have only 5 or 6 passes, or you can get really hardcore and break a scene down into 20+ passes (just breaking down the base elements into components).

In general, diffuse color, specular, reflection, shadow, ambient occlusion, z-depth are a good overall choices. Anything that lightens a scene is "add"ed in post, and anything that darkens a scene is multiplied.

mr Bob
08-27-2007, 08:42 AM
Funny you should ask Daniel , Im upto my elbows in cg cars right now, certainly consider these passes and get them into comp

Colour
Reflection
Spec
Matts
Glass
Occlusion

sugarandfat
08-27-2007, 10:34 AM
Cheers Bob.
What exactly do you mean by matts, glass and occlusion?
Do you have any examples of final comps and or render passes?

bwheels02
08-27-2007, 06:51 PM
All hail JasonA! He knows what he is talking about so take his advice whenever you can, or at least entertain the idea that he might know more than you... dum dum dum. :)

mr Bob
08-28-2007, 12:10 AM
Hey Daniel,

matts :- create a pass texture the body Red , Wheels Blue , Glass green etc. This will give you 3 different matts or masks as some call them to use in comp. You can use the R G B values in your compositor to then apply a mask to a particular area.
Its just one of many passes you could create and then comp !

How far have you got with your project

B

sugarandfat
08-28-2007, 08:54 AM
> 3 different matts or masks

Ah. Good call.

> How far have you got with your project

Haven't started just yet, it's a test for a contract, should be gearing up in a few weeks. The finished work will be a still, but needs to be very high res and quality.

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