Can't find this article...

[Marshall_Craft]

Hi, I know there's a link floating around in the forum pertaining to image resolution and GI settings (specifically LC and IRmap.) I tried hunting it down, but to no avail. Can anyone help me out?

I need to render a pretty high resolution image (around 8400pi x 6000pi) and I'd like to know how much of my GI I can scale back without losing my image quality. Thanks for any help.

- Alex

[Clifton Santiago]

|'m not sure what article you are referring to, but I've found that I can normally render the IR map at half the resolution of the final without noticeable problems.

In your case I would start even lower, maybe 1/8th resolution. Render the IR map, save it, set it from file, and then do a small region render to test the quality. Go up until it looks good.

As for LC map, if you save the IR map, you don't need to save the LC. Just reuse the IR map and set secondary bounces (LC) to none.

[Marshall_Craft]

Thanks; will do. One question though, to set the IRmap to 1/8th the resolution of my final image, does that mean I set the min samples to -8?

Again, thanks.


- Alex

[Tom B]

I think each time you decrease by 1 you halve the number of samples, e.g -1 to -2 is a halving, -3 would be a quarter and -4 an eighth. So if you render at 512*512 at -2 you can render 1024*1024 at -3. I know someone will correct me if I'm wrong.

[Clifton Santiago]

I've been told similar things by Vray experts. However basic math confuses me, and by trial and error I've not found such a direct correlation.

What I mean is that I think you get different (and better) results by calculating the IR map at say a Min/Max of -3,-1 at say 2000x1000 pixels and then reuse that IR map to render it at 4000x2000, than you would if calculate the IR map at -6,-2 at 4000x2000 px.

Does that make sense? Probably not...

[Marshall_Craft]

hmmm....looks like I'll start with the advice you two have given, and take it from there. Luckily I don't have an immediate deadline so I can tinker with the settings. Thanks.


- Alex

[RErender]

The general rule is that for every time the image size doubles the min/max values can be lowered by one with the same resulting detail so if the image looks good a -1/-3 at 840x600 then the detail will be the same with -2/-4 at 1680x1200 and so on.

[flipside]

I've been told similar things by Vray experts. However basic math confuses me, and by trial and error I've not found such a direct correlation.

What I mean is that I think you get different (and better) results by calculating the IR map at say a Min/Max of -3,-1 at say 2000x1000 pixels and then reuse that IR map to render it at 4000x2000, than you would if calculate the IR map at -6,-2 at 4000x2000 px.

Does that make sense? Probably not...

Yes the math confuses you

Ir map for -3/-1 at 2000*1000 is EXACTLY the same as ir map -4/-2 at 4000*2000 or exactly the same as ir map -5/-3 at 8000*4000 and so on. So no need to save ir maps and load them again. (in this case)

[RErender]

hmmm, guess i needed to put in the quote to be clear? :P

[flipside]

Yes you should

Sorry dude, hit the quote button without reading the rest of the posts first hehe.