Hi all… Sorry for double-posting, I posted this in the shaders forum by mistake.

Anyone good at reverse-engineering renders?

I have to do a car anim for an event, and am aiming for something along the lines of the enamel, metal flake look (pictured).  wondering if anyone has any tips, short of getting mforge (which sounds pretty complex for a short-deadline job, please correct me if I’m wrong). As its animating it needs to be sizzle-free too. Jens Moller has some nice renders in the GI seg of the gallery with a similar texture.... Jens if you’re out there, any pointers??

Also this render has a nice sharp highlight which you wouldn’t get without using an extremely high-res hdri file for the reflection - I’m guessing its a plane or something used as a reflection object - but if so how would you get the hdri-style 100% white highlight? Even with a 100% luminant white plane my test render comes out with a grey highlight… would making it a lightplane help?

Many thanks for any advice!

Rory

The reflection should be done with an HDR file in the RT reflection channel- you can adjust the re-mapping options to get the subtle fade around the edges. Perhaps a slight bit of “GI glossy” too.
Adding the Anisotropic shader (with a “normal” light source as the shader cannot “see” HDR lighting) with some blinn at a value over 1.0 may also give some of that sheen.

For the metal flake it is as simple as adding an image of fine grained noise in the diffuse and specular channels. Set the specular channel values to be “inverted” from the diffuse. Set the diffuse map to multiply- and adjust the “amount” slider for both maps “to taste”.

Hopefully that will give you a start.....

I made some HDR maps for just this type of thing......
They are 3000x1500 pixels. That should be good for anything up to 1080p animation unless you have extreme close-ups.
http://www.paralumino.com/x_cart/product.php?productid=16150&cat=274&bestseller=Y

Sample of something similar…
http://www.arketypedesign.com/Downloads/SmartDOF.mov
Dave

Some tips Jens gave me about car metals.

Silver cars have two reflection layers, 1 layer is raytrace, another is heavily blurred reflections (specular) of the silver particles (like Dave said, put a noise map in here).

Reflect an HDRI and start with a reflectivity of 0.2.

You don’t need to use reflection falloff.

If your specular doesn’t look right, try using GI Glossy instead.

Hope that helps,
Ian

Ian - 26 August 2008 09:42 AM

Some tips Jens gave me about car metals.

Silver cars have two reflection layers, 1 layer is raytrace, another is heavily blurred reflections (specular) of the silver particles (like Dave said, put a noise map in here).

This is actually true for all cars that have a metallic coat, in contrast to unicolor coats.
And to achieve a good looking render, i heavily recommend to render out all your passes seperate (diffuse, reflection, metallic, occlusion as your minimum collection of passes) , then create the final image in your compositing app.

Hi, I have a simple solution.
In my car animation I will use a simple noise b/w map for sub-reflection carpaint. Next I use a white square top for simulate glossy reflection and HDRI map for all remaining reflections and illumination. This is some example.

Many thanks everyone, some great tips! Its great how motivated you guys are to share your knowledge. Thanks again. Thought I’d share how it was going after day 1… heres some renders of the metal setup. BTW the car’s a dummy for one still to be provided.

At the moment it has a dome reflection object with a b/w ramp on it, plus a square as per gianluca’s tip. Experiments with hdri reflections dont seem to give the hard-edged look to the reflections - seems like you need objects.

There’s 1 light with a soft buffer shadow placed near the square reflector, to pump up the highlights - not ideal though as it insists on giving highlights to the bottom of the tyres, where there should be precious little light. I also had to do an exclude set on the floor for this light otherwise you get nasty buffer shadows obscuring the GI (adaptive mapped) floor shadows. Thats why the floor’s so dark! If you don’t have shadows it illuminates everything. Tried a soft raytraced shadow but the render times leapt thru the roof for no appreciable benifit.

The texture has an anisotropic shader plus a granite (noise) underneath - starting to work, it seems like 90% of the battle is lighting and placement of the reflections. Getting the edges to catch the highlights etc. The model’s pretty detailed and itd be nice to get as much as possible in there - crunching up the GI primary rays works a bit, but any tips would be welcome - maybe I’ll try an occlusion pass to crunch the blacks and bring out the details (eg doorframes etc). Be fun to play with the multipass options for this one.

Will post something when its further down the track. Getting the thing to render noise-free in under 10 mins a frame will be the trick I think!

Cheers

Rory

Rory,
there is some very compelling material insights coming out of this post.  I’ll be very interested to see what your solution is visa-vis GI for the animation.  Especially if you’re going to see inside your car, as you’ll have to solve the secondary ray issue.  If you can use secondary lights as opposed to secondary rays, you’ll be much faster.  Maybe set them up as a ring around the car.  You might take a peak at this tutorial for some help with the GI and reflective/transparent stuff.  It will help you optimize.

http://www.eitechnologygroup.com/forums/viewthread/486/

It’s looking like a great start.  Can’t wait to see it move.

Yon

A couple more eg’s… some problems have surfaced (he he) with the model - some polygon normals flipping etc. I converted the obj source file thru obj2fact 2.1. Does anyone know any reasons why I’d be getting these flipped polys, and how to fix them? Esp noticeable on the headlight glass and above the front wheel.
Cheers
Rory