dirty Race car

[discocandy]

I've been asked to do some retouch on a 3d car but the fun is they want it to look as it has done a long race like this image:
https://fbcdn-sphotos-h-a.akamaihd.n...85658049_o.jpg

I already tried making ink splatters on paper, make a brush of that and put that on the car.
I tried it with various brushes on layers to build up the dirt and give it a flow.but cannot get it as realistic as I want.

Any ideas how to do this??


regards, discocandy

[Repairman]

Re: dirty Race car

Even dirt flecks will be distorted on the contours of a car. Find a picture white rally car with mud spatters and you may be able to get a mask of the shapes! (try google images). You'd be lucky to get the perfect shape but with a few patches and rotates you'll get there. You could even find a light colour car in the street this time of year with a load of grime on the bonnet. CGtextures.com have some nice free splatter effects if you want to go that route!

[shift studio]

Re: dirty Race car

If you have access to the 3D car and software (photoshop extended possibly), you can add your dirt to the diffuse and bump channels of the material before rendering the car. - this'll give you realistic contours and lighting and shadows.
But alas - I suppose you'd have already done that if you had access.
So, otherwise Repairman's and your (brushes, layers, blending, transforming etc) are likely your best bet.
--Shift Studio.

[kav]

Re: dirty Race car

If you have access to the 3D car and software (photoshop extended possibly), you can add your dirt to the diffuse and bump channels of the material before rendering the car. - this'll give you realistic contours and lighting and shadows..

I wouldn't personally do it this way. I'd paint a dirt map with an included alpha value, UV the car, and apply the dirt as its own shading network plugged into a layered or blend shader or whatever the renderer in question decides to call it. Otherwise you'd have a glossy coating over your dirt. It still relies on the OP either painting dirt or extracting it from other photos at an appropriate resolution with layer masks intact. The layer masks would be fed to the shading network as alphas. If it's for something like a video game a layer stack might be computationally prohibitive, in which case you may have to just subtract the dirt contribution from the spec map.

[shift studio]

Re: dirty Race car

I wouldn't personally do it this way. I'd paint a dirt map with an included alpha value, UV the car, and apply the dirt as its own shading network plugged into a layered or blend shader or whatever the renderer in question decides to call it. Otherwise you'd have a glossy coating over your dirt. It still relies on the OP either painting dirt or extracting it from other photos at an appropriate resolution with layer masks intact. The layer masks would be fed to the shading network as alphas. If it's for something like a video game a layer stack might be computationally prohibitive, in which case you may have to just subtract the dirt contribution from the spec map.

Geez, my point was, add the dirt before rendering - it goes without saying the OP will have to do whats appropriate to have it look like dirt on paint, and not shiny brown paint bumps.

-- shift studio.

[kav]

Re: dirty Race car

Geez, my point was, add the dirt before rendering - it goes without saying the OP will have to do whats appropriate to have it look like dirt on paint, and not shiny brown paint bumps.

-- shift studio.

In spite of the wording, I didn't mean for that to sound like criticism. I just use other posts as jumping off points at times. I should have probably mentioned your way would work too if they at least made sure to add a dirt contribution to gloss and reflectivity maps or the appropriate channels of the shader. There is a lot more to it. The problem is that it sounds like the OP is learning from scratch on a job with this one, which is not so fun.

[shift studio]

Re: dirty Race car

Yes the solution I presented was a simplified overall approach to the problem, execution would require plugging the right things into the right channels which I didn't put as much thought into as you did.

Problem solving on the job can be a good thing, it forces you to find a perfect solution which you may not ever fully realise if it weren't for a commissioned project.

-- Shift Studio.

[kav]

Re: dirty Race car

Problem solving on the job can be a good thing, it forces you to find a perfect solution which you may not ever fully realise if it weren't for a commissioned project.

-- Shift Studio.

Well yeah I agree with you there, and I liked your post, which was why I quoted it. You write good responses, and you hit on a topic I really really like. Texturing is a topic in itself. The real question here is how good it needs to look. If it needs to look amazing at a high resolution, the OP is probably going to need a lot of photos to pull from. The thing that makes way more sense about getting it in the texture map instead of post is that it's actually reusable if they change lighting or something that way. Otherwise you'd have to redo it for any changes. I have no idea whether the OP has access to the original asset or scene.

[Repairman]

Re: dirty Race car

Problem solving on the job can be a good thing, it forces you to find a perfect solution which you may not ever fully realise if it weren't for a commissioned project.

-- Shift Studio.

Too right Shift! This should be engraved on a brass plaque and superglued to every retouchers monitor!

[shift studio]

Re: dirty Race car

Thanks guys (Kav and Repairman)
I also like texturing but am no expert at it yet.

Now, discocandy - how is the progress?
--Shift Studio.