DArnaez

Hi guys! I need you help again. From 2 or 3 days I was trying to render a big image and I don't know what I'm doing wrong... but I leave it rendering all the night and in the morning it going for the "1 or 3 pass". Jesus!!! of course I cancel it. I change some parameters and the same... here I show you some of my parameters. Ok it is really big (2560x1400) but is it logic having 2 Gb Ram??? . I don't know what is the better parameters for exterior scenes like this one.

It has only one direct light. May be te DOF that I use in the render parameter are doing slow the render process but... is too much!
The DOF parameters are Aperture 3 and subdiv 13. (I don't check "sides" because I haven't idea for what is that)
Can anybody help me? If is necesary I can upload the Max file. Thanks!!!

Attached Images

vray_render_parameters01.jpg (243.2 KB, 111 views)

notamondayfan

ur image doesnt work. try using the file upload thing here

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skogskalle

you have way too high settings for your Irradience map. You have the min - max settings at -2, 0 which is great for small renders, but its too much for your 2560x1400 render. try using -4, -2 instead.

i dont know how many subdivs you have for your lightcache, but for a simple exterior like this you could set it to maybe 2000 and it should still calculate fairly fast.

DArnaez

Ohhh.... I always beliaved that for good results, the irradiance map must be up to -1, 1 or up to 0. I was wrong? Wow! It will to keep good definition?

The same is for light cache. I was thinking that for to reduce the time render it must be less to 1000(the default). In this case I put on 400.
Could you explain me about these wrong concepts that I have? THanks Skogskalle!

skogskalle

irradience map settings depend on the size of the render... so if your render looks good with settings -2, 0 at 640x480 you get the exact same quality with -3, -1 if you render at 1280x960, or -4, -2 at 2560x1920.

The time it takes for the lightcache to calculate depends on the scene and not the size of the render (I think). So a complex interior will take lots of time even at low settings, but a simple exterior will be fast even if you use higher settings...

dynaman

wait a sec!
my production renders are usually about 4800 x 3600. so you're saying that if i get a good IM result at 800x600 using -3, -1, i could go as low as -8, -6??

i find that hard to believe, but maybe i should give it a test. how much do you think it would speed up the pre-pass phase?

bayvan

You allways should check the help files becouse not all of them are useless. This is from the vray help that can be found here http://www.spot3d.com/vray/help/150R1/

Sorry for my englih
Best regards'
bayvan

bayvan

You allways should check the help files becouse not all of them are useless. This is from the vray help that can be found here http://www.spot3d.com/vray/help/150R1/

Sorry for my englih
Best regards'
bayvan

dynaman

thanks - i did read that, but it seemed a little vague.
i was running some tests based on this principle, and i'd have to say at this point it seems inconclusive. on a 2400x1800 image, there is a noticeable difference using a max / min of -4 / -2 vs. -5 / -3. the -4 / -2 was slightly better on my test scene, but i do think you could get away with the lower values in a lot of cases.
anyway, glad to have seen this thread as it will save me some render time in any case.

hhoa_kts

I think it can help you something (from vray.info)
irradiance min/max settings vs. image resolution
posted by Wouter Wynen
archived on 19.9.2003

Hi,
from what I gather the irradiance map presets are resolotion dependent and optimized for 640x480......
does that mean that if I wanna double or more the render size (say 1200 or 1600 wide) will I also have to double my irradiance map settings like HSph. subdis and Interp. samples?? what about the min/max rate??

Follow-ups
The irradiance min/max settings are indeed resolution dependant (the presets are just different combinations of the irradiance map settings, min/mac, clr, nrm, dist, etc...). The prepasses are calculations of irradiance map for a lower resolution of the image, and in the following prepass it uses this info to refine the solution on a bit higher resolution image etc.

If the GI solution in a render looks good on let's say 800*600 with irradiance to -3,0 and you then change the res to 1600*1200, you can decrease the irradiance settings to -4,-1. (so -1 if you double resolution). This will give you almost exactly the same irradiance map.

Example: If you calculate irradiance map at -3,-0 for 800*600, this means the following:
prepass1: GI calculated for image with resolution 100*75 (=800/2/2/2 and 600/2/2/2)
prepass2: GI calculated for image with resolution 200*150, with the info it gathered from the first pass (=800/2/2 and 600/2/2)
prepass3: GI calculated for image with resolution 400*300, with the info it gathered from the second pass (=800/2 and 600/2)
prepass4: GI calculated for image with resolution 800*600, with the info it gathered from the third pass
Because each new pass uses the rougher info from it's previous pass, vray knows where the more important (detailed) areas are, and therefore doesn't need to calculate more samples in the less detailed (flat) areas.

So if you want the same irradiance map info for the image @ 1600*1200, use -4,-1:
prepass1: GI calculated for image with resolution 100*75 (=1600/2/2/2/2 and 1200/2/2/2/2)
prepass2: GI calculated for image with resolution 200*150, with the info it gathered from the first pass
prepass3: GI calculated for image with resolution 400*300, with the info it gathered from the second pass
prepass4: GI calculated for image with resolution 800*600, with the info it gathered from the third pass

HSph subdivs is the same as the hemispherical rays of fr, they only need lower values in vray. 50 is good for almost anything, try lower first, and if there are too many artifacts, go higher. Interp samples defines how the GI info at neighbouring samples is merged into each other. Higher values will tend to blur the solution, so the image looks smooth but looses detail (GI detail). Lower values will cause more splotches but better detail. So to get better quality, raise hsph and lower interp (but 50/20 is usually very good!)

Another important one is clr thresh and nrm (leave dist to 0.1 always). Both 0.3 is good, lower values will cause long rendertimes. Higher values speeds up things, but you loose detail again.

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