View Full Version : Need help about specular mapping!

02 February 2005, 09:03 AM
I am currently working on a project to visualize the office at work in a as photorealistical way as possible and one thing that currently holds me is a big, grey metaldoor that goes to the server room!

This is a matt paintjob with some clearpaint on top of it, what i notice is that the area where a halogenlamp hits the surface of the door, you can see various bumpiness etc etc instead of a clear reflection so i was wondering how to best simulate this effect in renderings... :shrug:

I have used bumpmapping earlier but i only want this bumpiness to show on the areas of the surface where the halogenlamp creates highlight and blooming etc... how do i achieve this?

Can anyone point me in direction of a decent tutorial for such specular mapping?
Any help greatly appreciated :love:

02 February 2005, 10:03 AM
Map noise to the specular colour and/or bump and take the bump value right down. Make the noise as small as possible.

Also mental ray--if youre using it--has a great blurry reflection attribute which helps to get more realism.

Have a look on for some shaders that may help you in getting the look you want.

Also for the lighting: Fake the light angle/intensity/etc/etc to get a good look. Just because, lets say, there is a light directly above the door doesnt mean that illumination has to come from that particular light. Its common for me to use several lights per object to acheive a good result and those lights will only illuminate that object (using light linking). It gives you more control and is how a stage or set would be lit.

02 February 2005, 10:51 AM
thanks, getting right on to it ;)

As far as the noise part, yeah i was playing around with it on specular color, but i never felt ig got em small enough!

And regarding blurry reflection attribute under mental ray for the shader, i dont get the quality on this as high as i want it... what attributes determines the outcomes of blurry reflection in the render?

02 February 2005, 11:30 AM
Sorry i misinformed you, i think 2D fractal is better than noise.
On the place2Dtexture node, in the repeat U and V the number needs to be somewhere like 1000.

For blur quality does increasing the value of reflection rays help. Production quality in the render globals may also help too.

02 February 2005, 02:35 PM
Thanks for your help! I was smiting maaad about not beeing able to get the textures small enough!
I mean, the details and im quite embarassed because of the fact that i didnt think of the u/v tilings! Im better then letting that detail slip me by ;)

You caught me off guard and im gratefull, thanks ;)

02 February 2005, 05:35 AM
You could also use a Layered shader, a Lambert at the bottom and a fully transparent PhongE or whatever on top, no bump in the Lambert, strong bump in the PhongE.

02 February 2005, 06:05 AM
I'd recommend what Stalhberg pointed out as well. Use a layered shader and no bump on the base layer, and a phong or whatever on top that is fully transparent and just spec, pipe something into the bump of the phong to break up the spec. Works very nicely.

02 February 2005, 06:16 AM
Ugh.....layer shader....

I find it much better to avoid that node all together. Just have your grey lambert shader "added" (or use the mix8 for more control) by a black shinny phong shader with its own unique bump map. Then pump that into a surface shader that is assigned to the object as a "root node." Pluging shaders into shaders is a very powerful pipeline.

02 February 2005, 06:45 AM
Yea, of course if using mental ray for rendering, mix8layer is the way to go, but he didn't mention mental ray =)

02 February 2005, 01:15 PM
I don't think mix8layer works on os x version of Maya if that is of any interest to individuals. At least I haven't seen it working yet. So for some the layered shader is perhaps the way to go. For the bloom you could use a ramp shader(as the top layer in your shading network) and under the special effects tab you could just give it a slight value in the specular glow.



02 February 2005, 01:29 PM
If I find myself layering any shaders I'd prefer seperate them into passes then fine tune in real time later in post :D

02 February 2005, 07:41 PM
Thanks for the interesting ideas stahl and bill, will look into it as soon as possible!
Yeah im rendering in mentalray, btw, so what is this mix8 you are talking so interestingly about? :P

Been away from work a few days now, probably back tomorrow so im gonna play abit more around with it then!

The reflectionblur input under mentalray tab of the shader is anyway completely unaceptable since the renderingtime jumps to my remaining lifetime everytime i insert it to a quality that still only looks slightly bearable!

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