V-ray questions

thomthom

If you ever need to render really really large.
http://asgvis.com/index.php?option=com_content&task=view&id=16&Itemid=57

solo

My 'Doh!" moment of the day, of course you can, what was I thinking?

Another one, how can I get a texture more crisp, I have a very low value bump 0.5 and low reflections set but the texture still seems ever so slightly blurry (customer did not pick it up but I did)?

solo

Where can I get a VrimgtoExr converter?

thomthom

@solo said:

Where can I get a VrimgtoExr converter?

http://asgvis.com/index.php?option=com_remository&Itemid=0&func=fileinfo&id=277

Main Download page: http://asgvis.com/index.php?option=com_remository

ASGVis' website is a pain to navigate after did had a redesign some months ago. They realise this and have a new version in progress.

http://www.vray.com/vray_for_sketchup/ vray.com is also a good resource.
http://www.vray.com/free_vray_tools/

@solo said:

Another one, how can I get a texture more crisp, I have a very low value bump 0.5 and low reflections set but the texture still seems ever so slightly blurry (customer did not pick it up but I did)?

Hard to tell without seeing. But I assume you used a highres texture?
You could try the image samplers: http://www.spot3d.com/vray/help/150R1/examples_image_sampler.htm#ex5

solo

Thanks for those links mate.

Yeah the website is a mess to navigate.

I overcame the texture issue, I got a clue from Nomeradona on the Podium site about increasing the texture reflection subdivisions and it worked like a charm.

Now I ask yet another one... I need to show reflection on glass and some brushed aluminium, but I do not want to use a background image or hdri atmosphere, I was hoping that I could force reflections only on the reflective surfaces. In Vue one can force a reflection map globally for all reflective surfaces without effecting the lighting, is this possible with Vray?

thomthom

Yes. You can do that on a global level if you go to the Reflection map in the enviroment. Or on a per material level by setting the Reflection map in the Maps section of the material.

dalomar

I just happened to be sticking my head in over here, so I figured I'd answer the Adaptive Amount 0.85 question. There are two main techniques that V-Ray uses to speed up a rendering; Early Termination and Importance sampling. I won't discuss the first one (that's another post), but the second one is basically the idea that values that have more potential to affect the scene should be sampled more accurately. In layman's terms, brighter areas get sampled more than darker areas do. The Adaptive Amount setting controls how much of a fall off happens between sampling the brighter areas and darker areas. We want some sort of fall off as that will make the rendering quicker, but with too much of a fall off darker areas my be undersampled leading to splotchiness and other issues.

The "goldilocks" number for this setting is 0.85. Any higher (>.85) and the sampling can be compromised. Any lower (<.85) and the rendering will likely be slower without much visual difference. Note that this is more of an issue when working with Irradiance Mapping for primary bounces. If you happen to be using DMC, they you can increase this a little higher than .85 (but still not to 1) without as much of a chance for artifacts.

solo

Damien, thank you for taking the time out to explain some of the technicalities of Vray and welcome to SCF.
It's always a good thing when developers are able to consult and advise on open forum, I know you are very active at ASGvis and glad you have also 'broken the seal' here too.

My next question is regarding displacement (I'm sure that this is a well covered subject on the vray site, but for those who are new or in a deciding capacity as far as render engines goes I will ask my questions here)

I have been trying to master displacement on simple objects before using it on any real projects, I have noticed that it totally kills render times which is expected and in line with most other render apps. I have found a few strange behaviors however, below is a simple SU model with a grass displacement on it, it rendered perfectly the first time but when iI decided to add the white band the render was flat without any displacement, I then made the band a group and rendered and it worked again giving me the result below. My question is... does the grouping of two material adjacent to another where one is displaced and the other not have any significance?

[flash=560,340:2rgr8gua]http://www.youtube.com/watch/v/fBDTBV8qNWg[/flash:2rgr8gua]

AcesHigh

this grass worm is really alien!

dalomar

Grouping does play an important role in VfSU knowing which faces to displace. The reason for this is that in order to keep the displaced mesh all continuous, V-Ray needs to know where those edges are and adjust the normal when approaching an edge between two displaced faces. Since the object was grouped correctly before you put the white band in there, adding it most likely muffed up the grouping in some way. One you regroup, then everything gets sorted out and it works.

The option that I was describing above is referred to as Keep Continuity. I don't recommend turning it off, but here's a small example of what it does...from Spot3d.com

http://www.spot3d.com/vray/help/150R1/examples_displacement.htm#example5

gaganraj

damien,

any word on vfsu for mac?

thomthom

Solo. Would you mind sharing your grassy worm?

solo

Sure thing, it's bit heavy as it has a large texture and a SDS form.

I included the displacement map incase Vray does not automatically map to it.

vray displacement.skp

thomthom

Thanks. I haven't tried to displace grass yet. But I liked your sample.
Was curious to how the displacement looked like. That's a PS noise generating filter, right?

solo

That's a map I got online with the grass when I was looking for a displacement example in order to learn.
I have been playing around using PSP making my own noise maps and concluded that the finer the noise the thinner the blades and visa verse.
I also tried squares and dots and they create some really cool effects, especially using a variety of grey shades one can get varying hieghts.

solo

Using the above displacement map I mapped another texture onto a low poly sphere and it turned out pretty good, I did use 'soft focus' in PSP, I believe it's called 'Bloom' in PS.

solo

Last one for the displacement tests, using a single face (no thickness) with a texture and displacement.

I believe displacement is under the belt, now the next thing I need to get a grip of is D.O.F, anyone got any good tips that can help?

thomthom

The rug and fur displacement looks the best. I've yet to see a grass displacement that works up close, But it does work for smaller patches seen further away.

DOF:
You must use Physical Camera.
The "Override Focal Dist." only takes inches as it's unit values. Nomatter what the model settings are.
Once you've set the focal distance, adjust the F-Stop until you get what you want in focus in focus, and adjust Shutter Speed or ISO to compensate for changes in light

Tip: while you dial in your DOF, render small and use "Override Materials" under the General Switches flyout to cut down render times.