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royterr
09-06-2007, 04:26 AM
i have been trying to mimic this red material for days now,
i tried the mia_material,blinn,car_paint, didn't succeed .
how can one achieve this distinct specular effect while being neither reflective neither glossy.

any suggestions?
http://www.aedii.qc.ca/v2/fichiers/uploads/section_4/2629.jpg

modernPrimitive
09-06-2007, 09:03 AM
I wouldn't even try that with anything other than a mia. Looks slightly fresnel to me. Reflections seem to be blurred by a bump but you might still need to lower the gloss from the default. Keep reflections reasonably low but use strong lighting - then you should get the very subtle environment fresenel reflections but strong "directional speculars". You might also try highlight only?

royterr
09-06-2007, 02:41 PM
I wouldn't even try that with anything other than a mia. Looks slightly fresnel to me. Reflections seem to be blurred by a bump but you might still need to lower the gloss from the default. Keep reflections reasonably low but use strong lighting - then you should get the very subtle environment fresenel reflections but strong "directional speculars". You might also try highlight only?

i can not use strong lighting because my object is in the shade.
can you tell me more precisely what kind of setting should i use to fresnel.

Sphere♥
09-06-2007, 03:23 PM
Looks like a reflective coating with a simple bump map to me.

modernPrimitive
09-06-2007, 03:26 PM
You can see the secondary reflections of the lamp above the front tyre so I would say it is reasonably reflective, but I can't see much reflected from a facing angle (this could also be that there is nothing bright in the environment at this angle), so I think it is somewhat fresnel. I'd leave the defaults fresnel setting and tweak them later if necessary.

I think your main issue is lighting:

You should be able to get the kind of strong speculars by using stronger area lights with decay (perhaps quadratic) so that the diffuse is still subtle for shade or place incandescent objects (like a plane with a surface shader with white colour - but pump up the white's V to a higher than 1 say 5 to start with) to create the appeareance of strong speculars via reflectivity. (speculars are actually a type of reflection) If you pump the V value high enough and your paint material has a very low reflectivity, it can still create very bright speculars but with very low reflectivity of the environment.

Think of it as faking HDRI - even thought the surface is low on reflectivity if an object is bright enough it will get a strong specular. (Alternately pull in a real HDRI file). Remember the brightness of the sky through the doorway is thousands of times brighter than the floor in this scene, so you need to get that kind of light setup going if you want to match up your shader to the reference.

I dunno - that's my take on it. You probably know more about shading and lighting than I do!

Do you want to post your scene perhaps?

royterr
09-06-2007, 04:49 PM
thanks for the info

teh scene is already posted in this thread (in the last post).
http://forums.cgsociety.org/showthread.php?f=87&t=532297

Sphere♥
09-06-2007, 07:00 PM
I downloaded the scene you mention to show you what I mean. I attached a default mia_material and only changed this: diffuse: red, reflectivity: 1 (no gloss), BRDF perp to view: 0.1, with a solidFractal bump texture, that's it. And since you said it's in the shade, I removed all lights (I deleted the sun), just added an environment to reflect and provide FG, that's it...
http://img210.imageshack.us/img210/9003/redpainttestxp3.jpg

royterr
09-06-2007, 09:40 PM
big thanks sphere,
the bump really helped me to achieve the right effect.

bwheels02
09-07-2007, 06:27 PM
Use a spec map.

royterr
09-07-2007, 08:18 PM
and plug it where in the mia_material?

modernPrimitive
09-07-2007, 09:23 PM
You would plug a spec map into reflectivity.

For an interesting "aged" effect like the reference photo has in some places on the frame (like where the back wheel joins the frame and other areas where the different pipes join together - it looks like the "varnish" has worn away here or there is dust / grime buildup - I would paint a spec map for that effect which will add a great deal of interest, variety and realism to your render.

If your UV layout is difficult to see clearly in photoshop, you can use the artisan tool to paint a greyscale map directly on the geometry. I find the Artisan tool is perfect for this kind of rough greyscale texturing - like painting weights I guess.

Master Zap recommends you try plugging it into Reflection Gloss instead of reflectivity as he says this is more "real world" than pluggin into Reflectivity but I haven't tried it yet. In this case you would just invert your map so that the whiter areas define the glossy parts and the black parts map to the blurry parts.

Should give a nice effect. I'd love to see some of the results you get with that.....

A subtle dirtmap would also be nice.

royterr
09-07-2007, 10:48 PM
modernPrimitive, thanks alot for the info.

here is what i got finally, it's not perfect but it wont be to close to the cam so that's ok.
http://www.aedii.qc.ca/v2/fichiers/uploads/section_4/1.jpg


i tried to map a specular map, it was slightly different, but i see what you mean,
it will show up more in a bigger and more detailed object in the scene.

i'll post my render as soon as i finish it.

modernPrimitive
09-07-2007, 11:16 PM
That's looking good.

hmm... you could use the texture that you've used to show where parts of the paint have peeled and exposed the underlying metal (I think it's plugged into diffuse on your shader) to create a spec map that defines the difference in the glossiness of the reflections between the painted and metal areas. (you'd have to remap colours or repaint it in photoshop).

It looks like you've already achieved this effect, the peeled areas look like they have lower and more blurred reflections - I can't really see the details without a close-up render. You could also use that texture and blend it with the fractal for your bump so that close up you get a bump where the paint has peeled. Traditionally I would have used a Layered shader to do something like this but painting maps is faster because MR only has to evaluate a single shader instead of two shaders and then composite the results. So using spec maps like this should theoretically give a faster render.

Anyway no good doing all that if you're not going to see these details in the render. Just thought I'd shed light on some of the techniques I use.

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