BrianKitts Posted June 13, 2005 Share Posted June 13, 2005 I've been using V-ray for about a year and I am getting to the point where I know the settings well enough to crank down what i need for optimal time vs. quality. But the one thing that has eluded me is the benefits of doing a single prepass versus multiple prepasses. I normally don't have that much of a breakdown with shadows, or splotchyness (new word for webster) that I can't control with adjusting subdivisions. So the question is, what is the benefit of multiple passes.... is there something I'm overlooking or not seeing, I've been pretty happy with the renderings I've been getting on one pass. attached is my latest single pass rendrering - C&C also welcomed thx in advance for your opionions -bk Link to comment Share on other sites More sharing options...
STRAT Posted June 13, 2005 Share Posted June 13, 2005 i usually render in a single pass too. i find a layered pass is usefull for ammending shadows or gi or reflection properties for example. i too would be interested to hear other people's experiences why they multi pass. it certainly isn't for speed. large render houses like ILM and Weta do it as standard. nice image btw. i'd just lessen the gi bounces slightly. Link to comment Share on other sites More sharing options...
ihabkal Posted June 13, 2005 Share Posted June 13, 2005 single pass here too. With animations I think multi pass helps more becasue rerendering the animation becasue you want darker or lighter shadows would make you miss the deadline. if you can do it for renderings why not? but I really haven't seen the necessity for that except on 1% of the projects. Link to comment Share on other sites More sharing options...
Victor Erthal Posted June 13, 2005 Share Posted June 13, 2005 I thought the muli-passes were used to get the best quality versus speed. Since it would only pass with a higher resolution where needded, instead of doing it on the whole image. But i guess i'm wrong. Dit it really render faster that way? Link to comment Share on other sites More sharing options...
ihabkal Posted June 13, 2005 Share Posted June 13, 2005 some plugin renderers re render the whole scene and extract from it reflections, then rerender the whole scene and extract from it specularity and then rerender the whole scene and extract from it shadows and then rerender the whole scene and extract from it beauty pass...etc.. kinda like my post : AWKWARD I think Brazil is like that. haven't tried Vray...Max scanline does all in one render. update. just tried mental ray and it renders each pass by itself. for ten different pass types it renders ten times. but it is fast in those that contain little info. Link to comment Share on other sites More sharing options...
Sawyer Posted June 13, 2005 Share Posted June 13, 2005 Just to clarify - you are talking about prepasses ("currently calculating prepass 1 of 4) not effects (reflection, z buffer) passes right? Link to comment Share on other sites More sharing options...
Victor Erthal Posted June 13, 2005 Share Posted June 13, 2005 Just to clarify - you are talking about prepasses ("currently calculating prepass 1 of 4) not effects (reflection, z buffer) passes right? at least i was talking exactly about that. the irritating prepasses. Link to comment Share on other sites More sharing options...
ihabkal Posted June 13, 2005 Share Posted June 13, 2005 that is as confusing as you might think it is Link to comment Share on other sites More sharing options...
Hao La Posted June 14, 2005 Share Posted June 14, 2005 Dirtmap is another solution , isn't it ? Link to comment Share on other sites More sharing options...
Craig Ramsay Posted June 14, 2005 Share Posted June 14, 2005 Hmmm i'm a little confused as to what you guys are talking about. If you mean multi layered passes then personally I only really use them for photomontage work where I may need to blend in shadows or reflections to match the photograph. If my renders are completely CG then I hardly ever need to use multi layered passes. Link to comment Share on other sites More sharing options...
STRAT Posted June 14, 2005 Share Posted June 14, 2005 we're talking about multilayer rendering. not pre-passing. pre-passing is a process some renderers use where you have no choice in the matter. Link to comment Share on other sites More sharing options...
Craig Ramsay Posted June 14, 2005 Share Posted June 14, 2005 Yeah that's what I thought. To be honest im still experimenting with multilayer rendering in Vray... it doesn't output layers in the same way as Max scanline does so i'm still trying to figure out how to comp the layers properly in Combustion/Photoshop Link to comment Share on other sites More sharing options...
jucaro Posted June 14, 2005 Share Posted June 14, 2005 I think Brian meant the other pre-pass rendering. The method in Vray Irradiance map engine where it calculates rendering pre-passes before actually displaying the actual render. And in the case of VRay's multi rendering layer capablities, i think it sux because its not integrated with max's render elements option. PSD layer manager is great but its kinda unforgiving in a network rendering environment especially in a DR environment. It adds a noticeable amount of rendertime compared to using PSD layer manager in a single PC rendering an image. Link to comment Share on other sites More sharing options...
Sawyer Posted June 14, 2005 Share Posted June 14, 2005 Seems like we are still talking about 2 different things. Brian, can you post your settings? I would like to see your subs if you can get a nice result like that with 1 pre-pass. I usually have mulitiple passes. Never thought about it, assumed the gi solution was refining itself but I may be wrong. Personally I have never done a effects layered composite. If I have to fake reflections in Ps I do it manually. Link to comment Share on other sites More sharing options...
ihabkal Posted June 15, 2005 Share Posted June 15, 2005 sometimes it is faster to have it done in one pass lik use 2 and 2 instead of 3 and 2 Link to comment Share on other sites More sharing options...
BrianKitts Posted June 15, 2005 Author Share Posted June 15, 2005 Sorry didn't get a chance to look a back at the thread till now.... Yes I'm referring to the number of irradiance passes done by VRAY, set in the Vray::Irradiance map rollout under Basic Parameters with your min/max ratings. As for multiple rendering passes in vray, I've never tried em... although it doesn't sound like there are many fans of it out there for vray. Link to comment Share on other sites More sharing options...
Christopher Nichols Posted June 16, 2005 Share Posted June 16, 2005 Two point to answer: Multipass irradiances are a hyge benefit as they only add more samples in the areas that need them. On the other hand, if you have too many passes, you tend to loose effeciency. I would say, as a rule of thumb, don't use more then 4 passes. As for rendering multiple channels (diffuse, specular, reflection, GI, shadows, etc...) it is something that you guys are really missing out on. When we were rendering "I, Robot" we rendered over 20 layers per robot in renderman. These are called AOVs (for Arbitrary Output Variables). Basically the rendering of the robot was just the "begining," all the real lighting took place in the compositing. The main issue, is that you may not know how to composite. How to add all those images together to get the same image as what was rendered. Once you understand that, then you can tweak your image SO much more than you ever imagined. Granted this is not simple. We created custom scripts in "I, Robot" to put together a robot. Want the metal more shinny? Move this slider. Want it more dirty? Move this. Want the shell more transparent? Want more SSS? Move this and this. VERY powerful. Composite changes are very powerful, and considering your rendering times on huge images, you may not want to have to do too many re renders. Render once, composite many. Link to comment Share on other sites More sharing options...
Tim Nelson Posted June 16, 2005 Share Posted June 16, 2005 How to add all those images together to get the same image as what was rendered. Once you understand that, then you can tweak your image SO much more than you ever imagined. That is something I still have not quite grasped, but would like to. Using Vray, how would one approach this? Or, something like psd manager AND Vray? Link to comment Share on other sites More sharing options...
Alex York Posted June 16, 2005 Share Posted June 16, 2005 hi guys. I've just started using VRay at work and I'm a bit miffed over the lack of pass control. any ideas how to set this up? I've noticed that VRay + MAX's Render Elements are not tied together in any way, so I guess that's out of the window. surely there's a way to output passes as seperate files from vray? I'm a pass junky (coming from XSI/MR) so any help with this would be awesome. cheers Link to comment Share on other sites More sharing options...
Craig Ramsay Posted June 16, 2005 Share Posted June 16, 2005 surely there's a way to output passes as seperate files from vray? Yep it's easy, just make sure the two highlighted check boxes are ticked, you have set and output path for the files and you have selected the output channels you want. The tricky part is compositing them all afterwards. Link to comment Share on other sites More sharing options...
Christopher Nichols Posted June 16, 2005 Share Posted June 16, 2005 That is something I still have not quite grasped, but would like to. Using Vray, how would one approach this? Or, something like psd manager AND Vray? the psd manager may be ok... I don't know, never used it. I like to put it togther the old fashion way... by hand... keeps you on your toes. Diffuse, * GI, + reflection, + specular (if you have it), then just use a series of mattes for objects and shadow passes. Of course a nice powerful node based comp package like Nuke or Shake is what really make a difference here. But you can still do it in AE, Just precomp each one (Diffuse, reflection, etc...) with the series of mattes, then plus them together. The only real issue is that Photoshop doesn't really have a true plus. But I have found that if you screen things twice, it generally adds up to a plus. Link to comment Share on other sites More sharing options...
Alex York Posted June 16, 2005 Share Posted June 16, 2005 ah at least there's something. although it's hardly a fully-fledged pass control system (a-la XSI). For instance, I don't see a way to create your own custom pass - you're forced to choose one of the presets. that seems awfully limited to me. hmm. perhaps the next version of vray will include a better pass system. gbuffers are very nice, but until it's possible to create your own passes from scratch (including some kind of override system as in XSI for really controlling what is output) then I don't see much use for them in production really. Link to comment Share on other sites More sharing options...
Christopher Nichols Posted June 16, 2005 Share Posted June 16, 2005 True true... additional pass contol would be great. Same as XSI, or renderman's AOV system. It is technically possible through the Vray SDK. Lets see what the Vray Standalone gets us when it comes out soon. Maybe it will have a shader language. Link to comment Share on other sites More sharing options...
Alex York Posted June 16, 2005 Share Posted June 16, 2005 trouble is that such a detailed pass system such as XSI's involves a huge amount of work on the actual package as well as the rendering engine. and since MAX already has the Render Elements (which seems OK) I doubt anybody will be keen on developing something that connects the two (MAX+Vray). I'll buy whomever does a large beer the standalone does sound very interesting too. Link to comment Share on other sites More sharing options...
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