HairInfoTex not working in hair / fur mod as opacity map - max 20123 / vray 2.3

[joconnell]

Hi Folks,

I'm trying to use the new hair material with the hair info tex map to control opacity and it seems like it's having a few problems. If you use the texture in the diffuse channel you've no issues at all and get a smooth transition from colour a to b, but if you use the texture in the opacity channel it breaks down and your gradient now becomes banded and steppy. It also changes length fairly heavily.

Here's some test hair with (clockwise from top left)

1. Just a solid diffuse colour as per the material settings.
2. Hair info tex in the diffuse slot, red to green.
3. Hair info tex changed to black / white, but still in the diffuse slot.
4. The same map as above put into the opacity channel and our diffuse tex turned off so it's back to solid green.



Any thoughts on why it's breaking?

I'm on max 2012 64, vray 2.3 official.

Cheers!

John

[Morne]

Hi John

In image2, in some hair on the right, I can also see the "step" its not a smooth gradient from red to green. Same in image3. But you're right, it's most obvious in image4. Maybe it's not a case of breaking in image4, just that its less obvious in the other images?

[Morne]

Also, is your windows desktop maybe not setup for 16k colours instead of 24 or 32?
(hmm no it wont be this, because then the image would appear fine on my screen, so nevermind, wrote before thinking nicely)

[joconnell]

Might be the jpeg compression doing this alright but there's a definite issue in the last image used for opacity mapping - shame, it'd be a hell of a lot handier to use hair in the main render than separate lighting setups!

[vlado]

Can you post the scene? I don't seem to be getting this here.

Best regards,
Vlado

[vlado]

Also, did you try the "Hair&Fur opacity" option for the VRayHairInfoTex?

Best regards,
Vlado

[joconnell]

Right, some of this is becoming clearer with hair and fur, this might be useful for other people too:

Okay so here's a render and a test scene showing a few different settings. From the documentation it seems like there's two methods of using the hair info tex depending on if you're using the max hair and fur modifier or something else like hair fx / ornatrix. In this case I'm using hair and fur. It also says in the spot 3d guide that if you're using the hair colour or hair opacity mode, that it will take colour a and b from the modifier material settings and ignore the colours set in the texture maps. So on to our scene file where we have 6 different planes, each with it's own unique hair / fur modifier and also a unique vray hair material in the mr shader slot of each modifier. In all material cases I've got the speculars and transmission turned off so you're only getting a solid diffuse look to the hair to try and make the results of the hair info tex as clear as possible. Here's what each is doing from left to right:

1. This uses position along strand in the diffuse channel of the material with a red and green colour in colour A and Colour B. This works fine aside from being blocky so as you suggested it probably isn't designed to work with the max hair / fur modifier.
2. This uses position along strand in the opacity channel of the material with a white and black colour in colour A and Colour B, the diffuse colour is set to blue. This works as expected with the opacity fading out but again it's a blocky result and as in 1, this mode isn't designed to work with the max hair / fur modifier.
3. This uses Hair&Fur colour mode in the diffuse channel of the hair material. As per the spot 3d docs, the Hair and fur color mode ignores the Color A and B settings in the texture and instead takes the colour values from the hair and fur modifier instead. The colours are set in the modifier to yellow and purple, look horrible but this is working as expected. No problems with this.
4. This uses Hair&Fur colour mode in the opacity channel of the hair material. As above the Hair and fur color mode ignores the Color A and B settings in the texture and instead takes the colour values from the hair and fur modifier . The colours are set in the modifier to white and black, so this is working nicely as an opacity map.
5. This uses Hair&Fur opacity mode in the opacity channel of the hair material. The tip fade is turned off for the hair in this modifier. As per the docs the Hair and fur opacity mode ignores the Color A and B settings in the texture and instead takes the colour values from the hair and fur modifier . The colours are set in the modifier to white and black, but in this case it isn't working as an opacity map.
6. This is the same as above, the info tex is set to opacity mode and the modifier has black and white as it's root and tip colour. The difference this time is that tip fade is turned on in the modifier and we're getting a fade out. So it seems that info tex takes it's transparency info from the tip fade switch in the modifier? I tried turning off the info tex in the opacity channel and left tip fade turned on, and the fade out stopped working, so it seems that you still need an info tex in the opacity slot to get things working.

So for the max hair and fur modifier it means that we don't get to use the bias controls? It'd be very handy to have slightly better control over the ramp from one colour to another in both colour and opacity but will it be possible to make this work, or will this be an ornatrix / vray fur only feature?

The other thing I notice from using multiple hair / furs in the same scene is that as you change settings on modifiers or in materials, the hair starts to get confused and the settings seem to switch around between objects. The only way you can get things back to normal is shutting down your copy of max and opening the file again, then things go back to normal. This might be a bit of a pain in the ass for bigger scenes with multiple characters, I'd imagine it's got something to do with the information hair and fur is feeding to vray. I'm going to try and get something really reproduceable but it's happened both times I've set up a test scene like this with 5+ hair / fur modifiers.

6_fur_settings_max_2012_x64.zip