Balcony view + caustics question

[PIXELBOX_SRO]

Hi all,
quick project for a client, did not have much time for further detailing.
C&Cs much welcome....

i woudl like to raise a question regarding caustics.
what should i do if i want vray sun to cast caustics through the wine glass?
i tried all sorts but nothing is hapenning when using vray sun... any hints possibly?
Thanks!



Best Regards

[Da_elf]

does the photon emitter radius encompass the wine?

[simmsimaging]

P-mapped caustics are a bit hard to setup IMO. You might want to try the directly visible hack. I also use this quote from Vlado as a guide:

The answer to that would depend on how you are lighting the scene. But in general, I myself would use just the normal caustics (not the directly visible ones), max. photons set to 0, and max. density locked to 1/3rd to 1/4th of the search distance. Then I would play with the Search distance to reach the amount of blurriness that can be tolerated, and then its just a matter of shooting more photons until they become relatively noise-free. Also, I would try to use relatively small light sources or point light sources (large area lights might take a very long time to clear up the caustics in this way). "


direct: enter this in the Maxscript listerner

renderers.current.caustics_showCalcPhase=true

One other tip is to try a very small search distance. For real-world scale glass objects I often use values of less than 1cm, often .05 or smaller before I really see much happening.

/b

[PIXELBOX_SRO]

Thanks for your replies guys!

Da_elf:
i have used vray sun to do this so i suppose yes ? ))

Brett:
at 1st i tried NON photon mapped caustics....unchecking "affect shadows" in both glass and wine.....no joy...the result was glass casting black shadow

Secondly, i ve enabled photon mapped caustics, but i basically hot the same result.


So this means that if i follow Bretts guide, I will have to setup another directional light with small emit radius shooting photons at the wine.
Do i have to setup this light not to cast shadows and only include the glass and the wine????

Vray is quite advanced renderer......why is it so much hassle to compute nice caustics just using vray sun and checking a box????? why faking it with another light????
Vlado?

[simmsimaging]

If you had GI caustics on I am not sure why you got black shadows from the glass. You shouldn't *have* to setup a separate light, not sure why you would think that based on Vlado's direction there, but you might find it easier to control.

I do agree though: getting good caustics is frustrating, and it's probably the only thing that has kept my eye wandering back to Maxwell

If you want to send a simplified scene I can see if I can get something going for you.

/b

[PIXELBOX_SRO]

will send the scene once i get to office Brett, thanks!

[simmsimaging]

So I have the caustics working fine, but the render is super slow. I know you mentioned that that material sub-d's are high etc, but I'm noticing it's only rendering on 4 of 8 cores on my workstation. Is there a setting in the file somewhere that might cause that? I haven't run into that with Vray before.

edit: not the light cache calc - the actual render process after all the pre-passes etc. That is still only using 50% of the CPU and there is no obvious reason for it

b

[simmsimaging]

I had to cut the render off with just a small crop, but here is the area of interest. I also attached the caustics render element so you can see what they are doing more precisely.

The caustics could be tuned up to get them sharper by lowering the search distance and increasing the caustic sub-d's etc, but I'm not sure it would be worth the render time hit for this small of a component in the shot. Up to you though.

I think the first problem you had was the one Da Elf pegged: I moved the sun and increased the photon emit radius to encompass the wine and table area. Beyond that there were other issues but I suspect they came from your playing trying to get things to work. The stuff I caught was:

- the caustic settings were a bit off: search distance was a bit high, max density was too.

- the glass and wine materials were set to "affect shadows" which would have negated the caustics too.

- The caustic multiplier for the wine material was set high (in the material wrapper) and the VraySun were set very high in the Vray Properites so those were turned back to default after positioning the sun and setting the caustic parameters a bit tighter.

- I also turned off caustics for the other two lights as they would have only slowed it down without adding much.

Last thing I can see: I think the reason you got black shadows when trying to get GI caustics is that you are not using Brute Force GI. I am pretty sure you have to use that to get GI caustics.

I am uploading the revised file for you and will email the link in a sec.

b

[PIXELBOX_SRO]

Hi, Brett
Thanks a lot!

CAUSTICS:
yep youre right, in the end i had all settings for caustics scrumbled
I think vray has problems merging certain objects from older scenes...it happened with vray FUR...now as you can see its hapenning with vray SUN. I have merged the sun with linked dome light from a different scene (where i have just sun and dome light linked-i use these to save time when lighting)....and voila...some of the light functionality is gone!

LOW BUCKET USAGE:
ive discussed this in other thread but it goes like this:
for some reason, Vlado said its due to specific maxscript command, the scene is using only 1/2 buckets when its ran on the workstation machine....when you run it over BB, it renders with full power.
Ive never ever set anything in maxscript though !!!
if you run the maxscript listener and add this line

renderers.current.system_numThreads=0

it will render with all the buckets

the weirdness of the merged VRAY objects is still here a lot of SPs back!!!


on another line....how woudl you setup the scene differently in order to get rid of the noise but render fast? do you find my settings whack?
the thing is..i coulh have set the subdivs lower, but i was fighting the noise in the different layers....the RGB pass looked right but the several separate layers looked weird.
sometimes i think i still dont understand the vray settings. )))

Thanks again for all your help!!!

Best Regards

[simmsimaging]

Ah, now I remember hearing about that bucket problem before, just the first time I have run into it myself. It must be a really odd one to find or Vlado would have crushed it by now

Regarding your settings - I am not well qualified to answer that, as I pretty much always use a variant of the Universal method and rarely venture into LC/IM world. When I do I tend to use Subburbs SolidRocks plugin to control the settings. Sometimes it works better/faster than the UM, and sometimes not. Rather than figure out why for any one scene I just test each early on and stick with whatever seems to work better for that scene.

Specific to your question though: I can't help much because with the problem with passes being noisier than the RGB I just let them be noisy rather than impact the primary render time that much, so I never bother trying to fix it. Easy for me, but I don't use as many passes as you seem to so it affects me less.

Anyway, glad to be of some help.
b