How to make a CD-like specular in a material?

Macattackk

Hey, so I would like to make specular in my material which is reminiscent of a CD. What I mean by that is Id like the specular to have a rainbow-like effect which splays out from the specular highlight. I don't want the specular highlights to be lines going toward the center like they do on a CD, I merely want the effect of different colored rings coming out from the circular specular highlight on an object.

My guess at how to do this is to use the light vector and apply a gradient texture sample to it but Ive messed around with this and am not sure how I would apply this correctly. Does anyone know how I might create this effect?

lpcstr

http://http.developer.nvidia.com/GPUGems/gpugems_ch08.html

Macattackk

Well Im not trying to make exactly what a CD is. Im just trying to get access to the fall off areas of a regular specular highlight and make it so that there rainbow colors which are basically rings around it.

I guess I just want to know if there is any way to access a specular high light and associate different colors to different intensity points within the specular highlight using an "if" node perhaps.

Obscura

maybe try this?
http://udn.epicgames.com/Three/AnisotropicLighting.html
this is not exactly what you want, but you should depart with that...

James Ordner

Is this what you're looking for?

http://udn.epicgames.com/Three/AnisotropicLighting.html

Edit: Just a minute too late!

Macattackk

Im not trying to do any anistropic stuff. heres a picture I made in PS of what I mean, just a rainbow specular based on the intensity of the specular:

AlexCatMasterSupreme

Not UDK but might be somewhat helpful possibly. http://www.digitaltutors.com/11/training.php?pid=303&autoplay=1

Obscura

Specular intensity is equal at this mat im sure.The colorization is obviously based on the anisotropic direction.think again

lpcstr

Macattackk wrote: »

Im not trying to do any anistropic stuff. heres a picture I made in PS of what I mean, just a rainbow specular based on the intensity of the specular:

For that, create a 1D texture with your choice of gradients and index it with NdotL. Use that as your specular color. Not very realistic if you intend for this to be some type of diffraction or interference effect.

Macattackk

Obscura wrote: »

Specular intensity is equal at this mat im sure.The colorization is obviously based on the anisotropic direction.think again

yea i guess they are just rings of color coming out based on a direction, I just thought that the anistropic flow had to be based on a single direction on the mesh and wouldnt dynamically follow the specular as if it were a smooth surface.

lpcstr wrote: »

For that, create a 1D texture with your choice of gradients and index it with NdotL. Use that as your specular color. Not very realistic if you intend for this to be some type of diffraction or interference effect.

I am trying to do a diffraction effect, just for a fantastical material which has an interference effect like that. I guess Ill check out your link and other sources more to see what that actually is. Is it not realistic because the order of the colors or because of the shape it's in?

AlexCatMasterSupreme

Ask in this thread.
http://www.polycount.com/forum/showthread.php?t=117309

Obscura

I did a quick test, and it works fine with the anisotropic lighting.
Its not perfect, but i think you should start with something like this.

Macattackk

thanks Obscura thats awesome, Id like to look at more of what that material is doing but in the picture a lot of the node labels are missing so Im unsure on some of it.

From what I can tell is that youre lerping fresnels with a normal map version of the anistropic map.

Obscura

what is missing, is just more lerps, and constant 3 vectors with different colors in it.and the whites are fresnels

Obscura

its not realy a normal map.i just multiplied constant3vector (r=0,g=0,b=1) to my anisotropicmap

Macattackk

ah yea i figured. Ill try this out on my own and probably figure this out but I guess im unsure on how it stacks the colors correctly in the different bands.
Seems like theyd be layerd on top of each other.

Obscura

search for the rainbow colors.i think, for a good result, you need to place that the same way as it is in the real rainbow

Macattackk

well I more mean that you are lerping different colors onto the specular based on that blue anistropic map but id think it would put all those colors in the same place on the highlight. But i think i figured out that what youre doing is using different exponents on the different fresnels to get different parts of the highlight.

Obscura

also maybe you need something like this at the diffuse, and maybe the opposite in the specular too, to get specular in the opposite direction.

Obscura

using different exponential would be working...but if you are look at some real refs, you can see, that exponential is changing, based on, where i am looking from

Macattackk

Well I messed around with it and got an effect I like. I just used a normal map that came with UDK to use as a test. It looks great in the material editor window, but in the actual level it doesnt look the same and doesnt really do any of the diffraction.

The lerp goes part goes into specular and the component mask goes into the anistropic direction.

edit: never mind, it is diffracting, I just need to mess around more with how visible it is. my anistropic is still not showing though.

Drew++

Was messing around with my anisotropic shader, and came up with this :V
The amount of blue comes from a node plugged into "CustomLightingDiffuse"


if you want to try it out... It's a MLM_Custom shader, lighting effects it.



the texture sample is this https://dl.dropbox.com/u/8510078/rainbowMap.png

Macattackk

wow thanks, thats a very interesting approach as well. I might mess around with that.

edit: i thought i was having trouble getting the anisotropic to show in game but i just wasnt seeing it to its full effect because of the way i was uving objects.

Obscura

omg thats really awesome...i thought the camera and the lighr vector is needed, but didnt know how to use it right.