Silver

[Shopper2]

Hi Guys,

Im having some problems rendering a silver coulerd oil bottle...as shown here

(http://img472.imageshack.us/img472/7...opvv935se3.jpg)

So its silver and has the effects of metal, but no reflection. I use the standard silver matte material in Vray and tweak the material subdivs to be around 33.

Anyhow, rendering 2 of these bottles at 2000x2000 px takes 9 hrs. Thats crazy. The reason for this is the reflection glossiness and highlight glosiness are set to 0.5 and the subdivs to 33. I ned this to get that silver effect.

Main settings are:

Image sampler :Adaptive QMC 1, 8 + antialias filter on at 1.5
QMC sampler: 0.95, 0.01
GI: irradience map 1 and light cache 0.85

Irradience map: -6, -2 66 sub divs

detail enhancement on- radius 30 and use for glossy rays on.

global switches: max depth 8 and ray bias 0.001.

If i lower the settings i get a lot of noise, so i have to set them higher resulting in crazy render times.

Is there a good tip for using materials with a low highlight / glossiness setting to speed up a render.

I really cant wait 9 hrs for something so simple.

Its like the silver of a macbook or a stand of a monitor....it looks metal but has no reflections, so you need to put the blur on, but then vray just freezes to really slow times....what is the major player to speed things up and keep it smooth besides the qmc sampler?

Thanks guys


Justin

[Micha_cg]

Re: Silver

Hmm, difficult. Blury reflection/refarction is the Achilles' heel of Vray for Rhino - "use for glossy rays" is the only shortcut. Interesting is, that the blury reflection contain so less image infos. If I remember right, Mental ray support a interpolation for this case, it means, the blury surface is calculated at lower resolution. Also I have seen at Vray for Max screenshot an interpolation option, maybe it's possible Vray too. but this dosn't help you know.

Two ideas: use less max Reflection/refraction depth and disable DE. DE makes, that the QMC is used at details. I have seen at my renderings, that this means too, that reflections are calculated by QMC. So, instead DE try to use better IM settings like max rate -1 or 0. My experience is, that the IM pass is done within a few minutes, the final pass is the critical pass.

An other experience is, that the rendering need more time with a studio environment than a simple HDRI without lights. So, if you can, use a HDRI like the classical building HDRI from http://www.debevec.org/Probes/. If you blur the HDRI for the reflection env (you could set for the bottle material only too), than the blur reflection calculation could be speed up too. So, only the reflection of the scene object maybe expensive for the Vray engine.
And the fastest way, but maybe not the best looking, you render the bottle in a blury HDRI environment only and add it to your scene per postwork. Try to keep the reflection environment for the bottle so simple as possible. Let me know, if a trick helps.

Maybe you render with more noise, additional you render the image with constant emitter colors and no GI .. and you use the second image for selecting the bottle in the first image and denoise the bottle only per Photoshop denoiser or other like noise ninja.

Last I render a room with blury windows between the room and next room. The calculation need very long too. I'm curious for speedup of blury effects too.

Good luck.

[dalomar_cg]

Re: Silver

I have a few things to add to what Micha said. First off I agree with disabling DE. For this image, it really isn't needed. And for a 2k by 2k image your IR solution seams about right. Maybe kick the max rate up to -1, but it would seam to me that it would be fine either way.

I do have a question to ask you...are the 33 subdivisions needed for a smooth lower test resolution, or the full res version? The reason why I ask is because typically larger resolutions can deal with lower subdivision values because the are essentially already subdivided by having more pixels describing a given area (also there is much less deviation or change from pixel to pixel). I would decrease the subdivisions as much as you could probably to somewhere around 20. Keep in mind that subdivisions are like exponents, so 33 subdivisions actually correlates to 2^33 or 8,589,934,592 samples while 20 subdivisions leads to 2^20 or 1,048,576 which is a significant difference.

Also, I would ditch adaptive QMC for AA because the settings that you're using are going to add some more noise in to the result, and also adaptive QMC is probably going to have you take more samples for the glossy reflections then Adaptive subdivision will. As I just suggested I would switch over to adaptive subdivision with a min rate of at least 0. For the max rate you can kick it up to 3 or 4, but that should be good enough.

Last notes. Lower the Max Depth. Unless you've got allot of reflections inside refractions in reflections you don't need it that high...4 should work, 2 should be even better. You can also increase the size of your area filter if you'd like to something like 1.75 or around there. At larger resolutions this won't be that bad and may help smooth out a little noise.

[Micha_cg]

Re: Silver

Small correction: the actual number of paths/samples is the square of the subdivs -> 20^2 = 400 and 33^2 = 1089, so the difference is a bit lower.

http://www.spot3d.com/vray/help/150R...s_lightmap.htm

Damien, what is the interpolation of Vray for max?

[dalomar_cg]

Re: Silver

Yea sorry about that. Its 33^2 not 2^33...I knew something was fishy when I typed in the numbers, but for some reason I didn't double check my self...sorry about that one. Either way the difference between 20 and 33 subdivisions is significant (render time wise), so any means in which you can decrease that value would be of much improvement to render times.

-Micha
I am assuming your are talking about the number of LC interpolation samples?? In that case I believe the default is either 5 or 10. In the case of Using LC for Glossies I'm not sure whether the interpolation values really matter. As far as I know the Interpolation values are only used for reconstructing the illumination at a given point. When Use for Glossies is enabled I would assume that elements of the raytracing structure are retained so that they can be reused during the raytracing of the glossy reflections, thus decreasing the need for a given number of rays (determined by the LC subdivisions and how valid they are for calculating a given glossiness sample) to be retraced. Did I get your question right, or am I off in right field (again)?

[Micha_cg]

Re: Silver

Damien, I don't mean the LC, but my last renderings show me, that the LC interpolation samples are a very interesting option. If you see blotches at the reflections, than a higher count helps. For example my car image at this post:
http://www.hdrlabs.com/cgi-bin/forum...m=1187252545/0
If I use default 5 samples, than I see blotches at the door reflection. The posted image use 30..50 samples, I'm not sure about the right number. It increase the render time like the IM samples.

Back to the reflction interpolation. I found an info here:
http://www.hdrlabs.com/cgi-bin/forum...m=1187252545/0
and I'm curious, how it works. Seems to be one of the current not implemented options. Maybe it's something like the MR interpolation that speed up the rendering.

[dalomar_cg]

Re: Silver

Well, the interpolation samples are going to blur the LC solution quite a bit. To a certain point its needed (without it you would get harsh edges from the LC samples), but like IR once you start bumping it up allot you've got a situation where the details of the solution are being lost. The other thing about LC samples is that the smaller they are (and typically I use from .01 to even .0025 in Screen scale) the noisier the solution will be, thus needing more interpolation samples to smooth itself out.

What you've got in the case of the reflections on the door is a few (maybe 1, but probably more like 3 or 4) very bright LC samples that are showing up in those reflections. They are probably bright from some odd sampling of the hdri because when you rendered with your adjusted hdri they seem to have disappeared.

As far as reflection/refraction interpolation in vfMax, I don't know too much about how it works (and it doesn't look to be explained in Spot3d), but if I remember correctly its basically a way of calculating reflections/refractions with a higher max rate when using IR. So basically you can have your main image calculated with an max rate of -1 and the reflections/refractions in that image calculated with a max rate of 0 or 1. I personally don't think that it would make too much of a difference in your situation because I think it has more to do with the sampling of the hdri as opposed to the IR solution. I also haven't really heard too many people sing its praises. Its not that its bad, I just haven't heard too many people exclaim about how lost they would be with out it (but i could be wrong). Also, is that the right link that you wanted me to look at for interpolation...its just the one for the hdri forum again and I didn't find anything specifically that mentioned interpolation

[Micha_cg]

Re: Silver

:-[ Sorry, wrong link should be this link:

http://www.spot3d.com/vray/help/150R...ial_params.htm