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View Full Version : layered shader with MR custom nodes??


sebast1an2
02-16-2004, 08:59 AM
hi, does anyone know how to build layered shaders with the mental ray custom nodes? i tried the layered shader from maya, but the custom shaders are not supported.. any idea?

thx

sebast1an2
02-17-2004, 01:06 PM
..and anyone know why the blinn & phong custom shaders have no reflectivity?? :shrug:

sebast1an2
02-18-2004, 09:10 PM
:rolleyes: :shrug:

bmcaff
02-18-2004, 11:17 PM
To get reflections with the MIB_illum_blinn you plug it in to the mib_reflect node input and set the reflect amount and then plug the reflect node into the material slot of the maya shader. The reflect amount controls the mixing of the base illumination node (black will give just illumination and white will give just reflection)

I have been trying to use mib_color_mix to create layered MR shaders but with limited effect. I plug in a base DGS shader and then a DGS/opacity shader but when I render, the alpha channel (where it is transparent) seems to brighten the base shader. It could be an alpha or opacity shader setup problem or the mix mode or even using the mix node itself. Here is the node diagram: layered.jpg (http://www.bmcaff.com/post/layered.jpg)
In theory this seems like it could work but something is going wrong somewhere. Mixing textures with alpha works fine for the color_mix node but using the shaders causes the problem. Suggestions??

sebast1an2
02-19-2004, 06:01 PM
Originally posted by bmcaff
..but when I render, the alpha channel (where it is transparent) seems to brighten the base shader...

hi, much thx for your reply! you have helped me a lot.:thumbsup:

..this " brighten up" problem is exactly the same experience i have made with this mib_color_mix.. and it really seems to be a maya related problem, cause it looks like it multiplies the brightness of the single shadernodes.. so lets hope someone find a other answer for this or it will be fixed in maya6:)

regards sebastian


p.s: do you know how to set up 38 identical mr area lights with the same settings?? its a damn nightmare to tweak the scenelighting inside every single lightshader...

p.p.s: i've seen your website. you are definitly one of my new favorite artist.. have you rendered mostly all these images with mentalray?:thumbsup:

bmcaff
02-19-2004, 06:40 PM
I haven't really spent much time on the problem but it could be what you said. Probably in Maya 6 we won't need these workarounds (fingers crossed).

I'm not sure what the problem with the lights is all about but if you want 38 lights just create the one MR light shader (say physical light) and then connect it to 38 duplicated light. To keep the area light settings just set them in the first light and then duplicate the other 37. Sorry if I am misunderstanding you here.

Thanks for the compliments, yes, everything is rendered using MR (There are a few older images which I did in Alias Studio Tools/Power Animator), I haven't used Maya Software Render since MR beta came out. I have a few new images which I plan to add maybe later this month (pending approval) so check back then.

sebast1an2
02-20-2004, 07:38 AM
hi, i've read that the customshaders will implemented in the hypershade in maya6.. so i think they won't forget to improve something for layered shaders:)

..the lights are not that easy.. i already have added a single physical_light to all these lights, but i also have to adjust the photon & area light settings... and it's damn timewaisting to do this for every single light. maybe there way to use a melscript to set all the settings?? i hope so..

greetings sebastian

p.s.: yes, please post some new pics.. can't wait
..i'm actual struggling with a indoor/outdoor-setup, similar to some of your architectural scenes.. i used a little yellowish infinite_light with dgs and gi/final-gathering, tweaked the setting a long time, so i'm using only 64fg rays and a few photons for smooth results...but i have big problems to get the right falloff between the in- and outdoor environment... so.. do you use a different exponent then 2.0? or maybe the normal maya shaders to get such a good light falloff?

lazzhar
02-20-2004, 09:48 AM
sebast1an2; where is the website of bmcaff, i'm curious to see ;)

sebast1an2
02-20-2004, 01:17 PM
??
i can't post his site without his agreement.. so you have to ask him;)

Emmortal1
02-20-2004, 03:13 PM
Ya if anyone finds this out, let me know. Layered shaders in mental ray are slow as piss and it's really starting to piss me off having my render time increase by 10 fold.

Emmortal

bmcaff
02-20-2004, 06:41 PM
It's www.bmcaff.com (I've updated my profile to include it, which I forgot to do earlier).

Sebastian, the In/outdoor falloff is really tricky to get right and especially so in a single render. In the interior scenes I have done (which feature alot of glass) what I have done is do a seperate outdoor render and comp it in photoshop. I generally use alot of layer techniques because of deadline requirements and the amount of control it gives me without rerendering (the usual reasons). I use a mix of Maya and MR shaders as the need arises and where appropriate. Maya shaders still offer alot of flexibilty and options over the current integration of MR.

sebast1an2
02-21-2004, 11:40 PM
hi.. someone know how to write a fresnel expression for the reflect- channel of the mib_reflect node? i'm trying to make a carshader but the mayaramp doesn't work and causes quadratic artefacts... any ideas?

Daniel Whitton
02-22-2004, 10:29 PM
Hey just reading you responses here. This may not be the place to post this, but I am trying to make a car shader as well. I have been testing with DGS shaders but I am not seeing fresnel reflections when mapping LDRI and HDRI reflections in my scene.

I just got the Rendering with Mental Ray book and was wondering if anyone could shed some light on volumic layered paint. It's from a render in the back of the book of a Mercedes SLK. I just can't find anything discussing this approach in the book.

Leslie57
02-24-2004, 06:12 AM
bmcaff:)
please explain this in depth :bounce:

Tierackk
02-24-2004, 01:54 PM
nice site bmcaff

you really have a good handle on outdoor lighting.

bmcaff
02-24-2004, 02:14 PM
Yeah, thanks. Actually outdoor lighting is rather easy.... it's the indoor that's a pain. More so when you have lots of windows.

Begger, I'm not sure that there is any need to explain in more depth as the technique only works in certain situations and there is a fairly significant problem with it. The hypershade diagram shows the set up and if you remember the opacity thread has most of the nitty gritty.
As for layered shaders in general I use then for decals & graphics alot (or used to before MR) and find that rendering them in a seperate pass is just easier. Sometimes I would have to produce illustrations of a products with many different variations in colour and finish so I would render out everything in layers to make the job acheivable in the time span.

sebast1an2
02-24-2004, 04:38 PM
hi, i think the main problem is the falloff of the "sunlight" in relation to mental ray's photon shaders and there transmissions.. i have tried many setups with mostly every possible combination of mr's custom lights and mr's shaders, and i came to the conclusion that there is something missing to get such a real outdoor/indoor setup...
..the last setup i worked on, was based on a textured skydome, a mib_infinite_light with zero exponent and completely dgs_shaders for the building[i tried it with the sponza atrium from cgtechniques.com].. i set all flags, deactivated some un-used settings like scanline etc. and rendered with gi and final gathering. it was really fast with less photons & final gatheing points [i think much faster then finlarender] and i got a really nice and realistic output from it... but it was still far away from results you get with renderers like Insight, vray or finalrender...

so.. where are the last 10% of mental ray's possibilities to match such "push a button renderers" like vray??? :shrug:

Daniel Whitton
02-24-2004, 09:18 PM
Thanks BMCAFF and Sebast1an,

I am trying out what you posted as well as a few variations. Maybe this can help. I recevied it from the mental images mailing list.
http://viz.cs.berkeley.edu/gwlarson/brdf/index.html.

Thanks again for your help .

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