resolution for saving irradiance maps

[heolson]

Hello! I'm working on a project where our final frames are being rendered at 1920 by 800. When I'm rendering the image to save out the irradiance map, do I need to render it at that size or may I render it at say 25% of the size to save on render time? Would this create artifacts or since it's stored in 3D space would it have no effect? Thanks!

[bigbossfr]

Hello! I'm working on a project where our final frames are being rendered at 1920 by 800. When I'm rendering the image to save out the irradiance map, do I need to render it at that size or may I render it at say 25% of the size to save on render time? Would this create artifacts or since it's stored in 3D space would it have no effect? Thanks!

Hi,
IR is resolution dependent. You have to render your IR with the same resolution, or, you can set the min and max or the IR (0 = same resolution).

[heolson]

Thanks!
-Hannah

[Neilg]

Hi,
IR is resolution dependent. You have to render your IR with the same resolution,

I guess it is, but you don't have to render it with the same resolution. I've not rendered an IR map at the same res as my main render for years.

As far as I'm aware, the minimum rate and max rate for your irradiance map is multiples of your resoution. Say your min is 3, and your max is 1 on a 1,000px render. The first pass will be done at 125, with 250 as the second pass & 500 as the last one. max rate 0 uses your full resolution.

I always drop the resolution of the IR pass because using a max rate of 0 on a 1920 wide render is too much, but half that (using a max rate of 1) isn't enough.

For big stills a max rate of 0 and set to 1500 wide is always enough for us, no matter if the final size is 4k or 7k wide.

[bigbossfr]

No it isn't, and you don't.

As far as I'm aware, the minimum rate and max rate for your irradiance map is multiples of your resoution.

So it is resolution dependent...

Say your min is 3, and your max is 1 on a 1,000px render. The first pass will be done at 125, with 250 as the second pass & 500 as the last one. max rate 0 uses your full resolution.

I always drop the resolution of the IR pass because using a max rate of 0 on a 1920 wide render is too much, but half that (using a max rate of 1) isn't enough.

So you have to bake your IR with the same resolution as the "final render" (we talk about the image resolution, not the "IR" resolution).
There is nonsense to bake the IR with, for example, a resolution of 1000px, min -2 and max -1, and render the final image with a resolution of 2000px.
You have to bake directly with the resolution of 2000px, and for this example, set the min to -3 and max to -2...

[Neilg]

I edited to 'I guess it is', but this:

You have to render your IR with the same resolution

Isn't true. You don't have to render the IR map at whatever your final resolution will be - it doesn't become useless when you scale up the final render size.

[heolson]

Thank you for your discussion. To further it, I actually was able to speak with a representative from chaosgroup in person today and he verified that the resolution can be a bit variable depending on how precise you want the final rendered GI to be. For something where the GI can be a bit vague, even going down to as low as 50% of the size can work, but of course you lose detail. So for something more precise, the 1500 wide can be significantly more accurate. Thank you for all your help!
Hannah

[bigbossfr]

I edited to 'I guess it is', but this:



Isn't true. You don't have to render the IR map at whatever your final resolution will be - it doesn't become useless when you scale up the final render size.

You talk about the IR resolution and i talk about the image resolution.
Like i said : render IR with an image resolution of 500px with min -2, max -1; is the same as render the IR with the final resolution 1000px with min -3, max -2.

So there is nosense to render the IR with an image resolution of 500px (min -2 and max -1). You have to render directly your IR with the final image resolution 1000px, and choose what you want for the IR resolution (-5,-4,-3.....).
The min/max set your IR resolution, not the image resolution (yes, you can set your IR resolution with the image resolution, but why to create an override ? min/max is here for this).

[Neilg]

(yes, you can set your IR resolution with the image resolution, but why to create an override ? min/max is here for this).

I'll quote myself here:

"because using a max rate of 0 on a 1920 wide render is too much, but half that (using a max rate of 1) isn't enough."

I could be rendering multiple stills from the same scene, some at 3k wide, some at 7k wide. It's easier to do a pass of IRmaps at 1500 all with a max rate of 0 than it is to start adding special max rate settings to each of the cameras. 1500 with a max rate of 0 is good enough for anything up to 7k. Saves on frame buffer memory too.

[Zdravko]

Whether you decide to use half resolution wilt the same Min/Max values or decrease those values with 1 point and preserve the original resolution, its a matter of choice.
How much the Irradiance map is optimized is totally up to the artist and the scene details.

[MoonDoggie]

Great quote, you didn't give yourself credit though.

This is really interesting advice. I'll try it out. Resolution set to 1500w, max rate of irradmap 0? Save that and go to town rendering a 7k image?

[Neilg]

Great quote, you didn't give yourself credit though.

This is really interesting advice. I'll try it out. Resolution set to 1500w, max rate of irradmap 0? Save that and go to town rendering a 7k image?

Yeah. drop reflection depth to 1 and switch off glossies too. Sometimes i'll use the VMC script to switch off reflections altogether (keep refraction on though!) and you wont believe how fast an irradiance map set to 'high' can be done. (this may make your render slightly brighter, depending on makeup of materials & how the scene is lit - not by very much, but just incase you see it happen it's to be expected)

[MoonDoggie]

Excellent, thanks Cubicle