Light Cache subdivisions

[Mats_O]

I am doing some hi-res stills. How many subdivs in the Light Cache do you use for different render resolutions? For a 1000x1000 and a 4000x4000 image?

[^Lele^]

for a 1k x 1k image, using 1k subdivs will lead to a shading rate of 1 for the lightcache (ie. as many samples as there are pixels, regardless of sample size).
For a 4k x 4k, the same amount of samples per pixel (shading rate) can be had with 4k subdivs.
My old script pack has a thing called LC calculator, which helps understanding just how many samples the LC should be casting, and changes the settings for you, if you so wish.

[zeronove]

Hi Lele

I've finally found some time to play with your LC script; here is what I get as an example

img res 640x480 - SS 0.02 - subds 1000
img res 1280x960 - SS 0.01 - subds 2000
img res 2560x1920 - SS 0.005 - subds 4000

So, my very rough conclusion is that:
every double resolution leads to half SS and double subds, is it correct?

What is still a bit unclear is why Vlado says to leave SS as is

http://www.chaosgroup.com/forums/vbu...ad.php?t=46787

Does it mean that, talking about the above example, for a 2560x1920 and forcing it with 0.02 SS then I should need 16000 subds! (theoretically speaking)

I'm pretty sure I misunderstood something, any suggestion?

[^Lele^]

Ale, i am NOT sure the idea of Shading rate is actually correct.
All i know is that it's something that by being kept consinstent gives me consistent results.
As for sample size, since the number in the VRay LC panel is expressed as normalised (ie. it goes from 0 to 1), leaving it at 0.02 means you have a sample size which is 2% of your total sqrt(MPx).
So changing that isn't needed when changing resolution (ie. it will always stay proportional to the image size, leading to identical GI quality for different image sizes, given an identical number of samples per pixel).

I am replying to the post i read in mail, which you likely edited in the while

EDIT: nah, it's the reebs :P i replied to the wrong link in the email, lol :P
EDIT #2: sample size has NO effect on the shading rate. So for a 2560*1920px image, which is a net total of 4.915.200 pixels, to have a shading rate of 1, REGARDLESS of sample sizes, you'd need the square root of the MPx, or in other words, 2217 subdivs.