Irradiance Map

[glorybound]

My understanding is you can reuse an irradiance map that was rendered at 1/2 resolution. Am I correct? Since you have to render twice, is this really a time saver? Do you do this as a last resort to render something that is typically to large for your system? What's the benefits, if any?

[andybot_cg]

it can save time if you only render GI, then load the map for the high res final raytrace.

[glorybound]

do you specifically save your Irr map at half resolution, to use it later for a high resolution final?

[glorybound]

mind you, I'm talking for single stills. I have done this for animation.

[super gnu]

ive seen a lot of people who swear by this in the past, but for the life of me ive never been able to work out where the idea came from, or what the advantage could be.

as far as ive always understood it, rendering your imap at half res is just the same as rendering with your min and max imap rates halved.


id love to know if there is any more to it than that, because i hear it again and again in different companies and ever since the very early days of vray.

[andybot_cg]

The only advantage I've ever found is with the LC pass. Setting the min/max on the irrmap (as super gnu metnions) gets the same effect. Sometimes with complex materials the GI calcs can take a long time at high res, but I haven't run into this for still images in a long time.

Also - I've not had any issues with different resolutions - doesn't have to be exactly 1/2.

[zeronove]

these are my beliefs about IM:
IM is resolution dependent
IM preset are based on 640x480 res
every time you double the resolution you can go 1 step down with IM min/max values
ex. you are fine with 640x480 and medium preset (-3/-1) then if your final render is 1280x960 you can change these values to -4/-2; if your final render is 2560x1920 you can change these values to -5/-3 and so on.
Obviously these are only a starting point; it's up to you fine-tuning on scene basis

Ps
for stills I've never find so useful saving IM to reuse it later because in the meantime I've for sure changed something crucial