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View Full Version : Iridescent - how to feather it?



Ramon
12-16-2003, 11:32 AM
Hello all.
I was wondering what types of shaders, or rather how I can create a shader that looks iridescent in only a certain area of the object - through either alpha maps or weightmaps. The effect would be like what you would see on the feathers of a wood duck - the way the iridescense fades in/out.
First off, would use interference , frensel or something else to realistically simulate this effect. If yes to fresnel or interference, I don't see where I can apply an alpha map or weightmap to them in order to taper and limit the effect to a specific area of the object/surface.
Thanks
Marry Christmas!

Malorie
12-16-2003, 04:07 PM
Use a Gradient color map in the color texture channel and use the incidence angle for the input parameter. Then use a weight map to apply it where you like on the object.

Malorie

Malorie
12-16-2003, 04:14 PM
Here's a real quick example without the weight map.

Ramon
12-17-2003, 01:45 PM
Malorie: Thanks for your response.
This is the look I am going for:

Notice the sheen and iridescense. This ofcourse is not a movie so you can't see how it changes (disappears) according to the angle from camera. I know how to produce the incidence angle of course through gradiants, what I don't know however is to reproduce the sheen look that this image has as well as limiting it to only a samll part of the object as it is in the duck wing image. Just a gradiant shader in the color channel wont make it look matallic, so I was thinking that if I place the same shader use for the color channel into the specular channel then I would have the "sheen" factor.
A question I still have, is that - can you still limit the range of these incidence gradiants through use of a grayscale alpha map image? If so, that would be sweet however - there is no option for loading an alpha image within the gradiant layer. So, do I create another layer and make this layer an alpha image - with my alpha image map loaded there? This might work but, I have had a chance to check this yet.
Also, what would then be the difference in using gradiants as opposed to using the Thin film, fresnel and interference shaders?
I would imagine that they would be more accurate yet I don't think that you could limit there effects as you would with gradiants due to the above mention use of the alpha layer. Gradiants would also allow for more flexability.
Thanks

Malorie
12-17-2003, 08:54 PM
If I see it right, it looks like you thought it through pretty good.

I'm not sure of the order (I've been away from LightWave all summer), but you would use your alpha to limit the placement of your gradient to only the alpha's tranpearent areas. You could also use weight maps to place the gradient only in the places that you want it.

I like to use gradients because there seems to be better, more intuative control over every aspect of a gradient as apposed to fresnel. The you can just copy your gradient into any channel that you like, including spec and reflect.

I think you're on the right track now.
Malorie

Malorie
12-17-2003, 09:14 PM
Here's a quick shot of a character I did last winter. I made extensive use of gradients for the colors and textures. I think the goldish tinge to his skin is sort of what you're looking for. It was done with the method discribed above.

Malorie
12-17-2003, 09:15 PM
Sorry, here's the pic.

Ramon
12-18-2003, 12:28 AM
Hey Malorie! That's a real nice example of what I was talking about. Yeah, I've been thinking about it a lot since I posted last. I agree, gradiants have more control over the color(s) you want to show. My application for this will be on certain areas of my dragon (work in progress).
Thanks for all your help!

Malorie
12-18-2003, 06:18 AM
You are most welcome.

Just glad I could acctually help. :)

Love to get a peak at the dragon when you're ready.

Malorie

Ramon
12-18-2003, 03:02 PM
Sure thing! I am deciding which scale/skin texture patter to place on him right now. I will try to post it up in a couple of days. I might put it in a new thread called dragon or something but, I'll let you know here as well.
Thanks

Ramon
01-21-2004, 07:06 PM
Originally posted by Malorie
You are most welcome.

Just glad I could acctually help. :)

Love to get a peak at the dragon when you're ready.

Malorie
Hi Malorie, I have a preliminary screen grab of the Dragon (or it's head rather). If you would like to see it:
http://vbulletin.newtek.com/showthread.php?threadid=16715&highlight=Dragon
But, I haven't applied the iridescents yet. That will be as we discussed, along the tail and will adhere to an alpha layer.
Tell me what you think so far.
Take care.