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Hi!

I've just bought Maxwell after playing around with the demo for a few days. I must say that it has improved a lot since I tried it some year ago! One thing that I haven't figured out yet is how to change the opacity on strands. I thought that I could just plug a gradient in the layer opacity but it doesn't seem to work? Is there a way?

Cheers

Hi,

The gradients in SI aren't supported yet, you will have to use a bitmap.

Have a look at this thread for general mapping info:
http://www.maxwellrender.com/forum/view ... 04&t=37792

If you mean the opacity from root to tip, then make sure the texture you are applying as a layer mask uses UV channel 0, which is the UV channel used for root to tip mapping. You can use a Maxwell texture node instead of the default Image node - this node has a parameter at the bottom to specify you want to 'Use Index' and set it to 1 for your layer opacity mask.

You can also find more info here with some examples:
http://support.nextlimit.com/display/knfaq/Fur+and+Hair

Thanks for your reply! I've actually done the steps that you suggested and I can put an gradient in the reflectance value without a problem but if I take the same gradient and plug it in the opacity texture I get the same transparency over the whole strand. Any suggestions?

Sorry, I ment set the Use index to 0, not 1. I'll make a simple scene and send you. Are you on 2012?

Yes, I'm on 2012. Thanks!

Just wanted to mention though, it will render slower if you apply layer opacity to the strands. It will be faster using the transmittance if you want semi transparent hairs. I haven't really found this necessary with the hair in Maxwell. The tip size usually gives a good impression of hair 'fading' out (in reality it doesn't really fade out it just gets thinner). What exactly are you trying to render?

Ah, ok I actually thought that it would be faster with the opacity. I just want to be able to make a gradient that makes the the strands more transparent at the root and at the tip. In other renderers where I have a lot of hair I sometimes make the strands square and just puts a gradient to fake that they are thinner so I don't get problems with the antialiasing and I also like to have a transparency at the roots for strands close to the hairline to get a nicer transition.


I've made an picture to show the issue. What am I doing wrong?

Hi again!

Have you had time to set up a simple example scene yet?

Cheers

Hi,

Sorry for the late reply....too much to do lately. I have indeed found a problem when mapping the Layer opacity, without mapping it works ok. But even when this is fixed my suggestion is to not use it. It's not efficient when rendering, plus it's not really the way to go in my opinion. I think the effect you want is based purely on the density of the hair strands, they start off fewer which when viewed at a certain distance gives that soft edge effect. Hairs aren't more transparent at the roots, for example:

http://mwallent.files.wordpress.com/200 ... 08hair.jpg
or this
http://img528.imageshack.us/img528/3310/hair1bi5.jpg

I just made a quick simple test using a weightmap connected to the hair. I wasn't sure how to do that so I found this tutorial if you need it:

http://forums.cgsociety.org/showthread.php?t=148218

A test with black hair, a better test than blond hair because of the higher contrast between the texture and black strands. I think it works nicely. I circled in the green area which is the look I wanted to get. It's because of the accurate shadows and GI you get that soft look, so there's no need for transparency tricks I think. It's a bit exaggerated ofcourse, didn't mean to make her look balding Also for better control with a weightmap I think the generating mesh itself needs to be a little dense, so you can paint more precisely. Or, use a texture as a density map.

Thanks, for your suggestions! I'll try them out. Maybe I'm to focused on the Mental Ray way of creating hair.