New to VRay

[Garryclarke]

Hi,

I've just bought a copy of VRay (just waiting for the paperwork to go through and the dongle to arrive).

For the last 10 years or so I've been a Brazil user, but as it's now officaly dead it's time to move on.

Are there any intro level tutorials I can read to help me switch over to VRay?

- Garry

[glorybound]

Welcome Garry! If you need help, this is the place to be!

[joconnell]

No, but here's a few thoughts.

GI:

With vray you've a split between primary and secondary bounces. The first bounce can have a tonne of sharp detail in it so you can use a high quality method for this, the secondary bounces are very diffuse so you want something quite soft. There's three main GI methods that you'll use time and again:

Brute force: Pretty much raw raytracing. Memory efficient and very sharp but potentially the slowest since it's per pixel. Big benefit is if your render is good enough in terms of grain / noise, then you'll never get an flickers or other things associated with a method that uses undersampling. When used for secondary you choose how many bounces you want GI to have.

Irradiance map: High quality primary bounce method. Starts out at a lower resolution image, and gradually refines using the angles of the scene geometry and colour values from where your light is hitting to only place detail in the corners or other complex area of geometric detail. Will fly through flat areas of architectural scenes and put in nice detail in the complex areas. Since it's undersampled can sometimes have flickering errors if it's calculated per frame but for scenes where the camera is the only moving thing it's possible to cache it and have it locked. Can only be used on primary.

Light cache: I'd use it for secondary bounces only, very very fast but mainly used for soft, ambient fill. It's effectively got infinite bounces so it's the daddy for filling out a volume of light in interior scenes. Same as irradiance map can be cached for scenes where you've got nothing but a moving camera.

As a very very simple rule, if you've got an interior scene and non moving geometry, use irradiance map and light cache with both cached to disk. Both high quality and great on render times and no flickers. For exterior stuff, the same can be great too. For scenes with animation it's a bit more fuzzy. If you've an exterior scene you can use brute / brute or brute / LC as most of your GI rays will hit an object once, then bounce off into the sky and die off so you get decent speed but also the convenience of only needing to see if your GI channels look clean to know you're not going to get flicker. With animated stuff a big issue is if there's a roof or not. Anything more inside than out will come with penalties since the lighting is way more complex so it's a toss up between risking irmap and light cache, or if it's a smaller object taking up less of the final frame, brute and LC.

Take a read of the gamma workflow threads so you get correct passes for nuke or after effects compositing or let the folks here know if you intend to burn in gamma or not.

The vray material is really really simple - mainly like the arnold material. Try to only use vray materials as the scanline or raytrace material won't give you information in render elements otherwise. If you want self illumination it's not in the main material, so you've to use a vray blend material with your main material in the base slot, and the vray light material in one of the coat materials.

The unified sampling system in vray can be a bit confusing at times - higher AA can make your renders longer and the quality worse. Get to know how to chase noise in your renders, mainly using the vray frame buffer so you can see each element as it's being rendered. The vray Raw GI and Raw Lighting elements will show you the quality of your GI and your direct light with no colour multiplied in, so you can use it as a diagnostic to check for grain (need more light samples) or Gi errors (need more GI samples). The raw reflection can be a bit misleading, vray takes the reflection component of each material and boosts it to 100% to make an almost chrome pass, but if you take a weak reflection and boost it that high, it pushes noise in so it's not a great reference for your material quality. The reflection element shows the reflections as the are in your final image, so it's a better gauge of if there's too much noise or not. That means more reflection samples in the noisy ones.

The sample rate element shows you what your AA is doing - red pixels mean high AA, blue is low with green in the middle. This is kind of the key to vray. As you up the adaptive DMC aa samples, vray tries to save time and in areas where it uses more AA samples, it balances out the additional quality it's calculating by reducing the light, gi and material sampling on the objects that it hits. All very well and good in theory but what can often happen is that it could be a nasty reflection from a hdri or bright light that's causing higher aa sampling - this could be easily solved with more material samples, or more samples in the light causing the highlight, but vray is trying to fix it with AA and inadvertently reduces the sampling on the two things that would solve the problem. Toni Brantincevic was the first to cover this here - http://www.interstation3d.com/tutori...yfing_dmc.html but the key to it is using the sample rate element so you know what your AA is doing in the scene, then using that as a base to judge if it's the AA undermining your other samples, or that your AA is okay and you just need a few more light or material samples.

Far as I remember you were mainly a VFX type operator but if you give a few indications on what type of work you're doing we could figure out things that are more relevant to your type of work and what quirks vray has in those areas.

[MoonDoggie]

Just wanted to say welcome. For best response and help times please post screenshots of any problems you're encountering.

[vlado]

Welcome to the forum! There are some basic tutorials in the V-Ray help index, along with examples for the stuff that's used most often here:
http://www.spot3d.com/vray/help/200R1/

For anything else, you can post here or contact our support guys directly.

Best regards,
Vlado

[Garryclarke]

Thanks for the replies.

I'll also have a good search/read of the forum as well and try not to post too many noob questions

I didn't use a lot of the GI features in Brazil. Just fairly basic settings, some domelight, linear workflow etc.

Thanks
Garry

[Garryclarke]

Hi,

Got my dongle today (xmas holidays caused a bit of a gap) I'm registered with my companies name so I look like a different user (I think).

Got it installed all seems to be running OK, I need to go and read some stuff from spot3d.com before I start with the newbie questions.

Thanks for the write up Jo, I remember your name from the Brazil forums. I work on mainly engineering subjects (oil rigs etc).

My first question (being lazy as I've not read anything yet) what is the equivalent of the Brazil image sampler settings? I used to set them to 0,0 when I was setting up lighting etc and then set it to 1,2 for final rendering. What would be the equavalent in VRay?

[joconnell]

In terms of image sampling - brazil does undersampling in it's main AA so the equivalent in vray is adaptive subdivision. The thing about adaptive subdivision though is it doesn't get a lot of the speed benefits of vray. I'd stick more with adaptive DMC aa and use the dmc noise threshold in the dmc sampler rollout to control the quality - 0.01 is standard, so larger numbers mean a higher level of difference between each pixel is acceptable - noisier results but faster renders.

These settings aren't perfect but it's not a bad place to get a single control for speed versus quality:

http://www.spot3d.com/vray/help/200R...nisettings.htm