2 Light Cache Questions - Glossy Reflections only, and Store Direct Light

[dangerweenie]

Hi,

I had a question regarding using the LC in V-Ray for Maya -

I understand that if I save an irradiance map sequence (animation prepass) while using LC as "secondary" GI, that once I switch to animation rendering and render my scene, I can use irradiance map for primary bounces and set secondary bounces to "none", because the secondary GI info was saved into the Irradiance Map during the prepass.

So when rendering with primary: IM and secondary: none, it looks the same as primary: IM and secondary: Light Cache, except you save the time you would otherwise spend calculating the Light Cache.

My question is in regards to "use Light Cache for glossy reflections". Is it possible to save the secondary GI info into your Irradiance Map, but also use LC just for glossy? Or does it do the same computation either way? I'm not sure what's more efficient - saving in the secondary GI info to the primary GI prepass, then tracing glossy reflections without LC interpolation, or just rendering the light cache anew every frame. I'm thinking the primary is quicker, though as with all things CG and rendering, I know it's a case by case situation.

Regardless, I'd like to hear the opinion of you guys.

Also, if I save my LC into my Irradiance Map, and "use direct light" is on, then I render with just IM and no secondary GI, does the direct light not get computed? Or does that only happen when LC is set to secondary?

On that topic, are there any attributes specific to the light cache that don't get saved into the Irradiance Map, or that don't come into play when LC is set to primary or secondary? I feel like the behavior of it changes substanially based on how it's used.

Sorry for the long post - thanks in advance for your thoughts!

[Svetlozar Draganov]

Hello dangerweenie

Is it possible to save the secondary GI info into your Irradiance Map, but also use LC just for glossy?

When Light Cache is saved into Irradiance Map , and secondary bounce engine (LC) is turned off - Vray doesn't use LC to calculate glossy rays.
According our tests - rendering with both engines ON (IM+LC) and enabled "use LC for glossy rays" - produce better rendering times than rendering with just first bounce engine (IM).

If I save my LC into my Irradiance Map, and "use direct light" is on, then I render with just IM and no secondary GI, does the direct light not get computed?

The situation here is similar as the previous one - Vray won't use LC to "store direct light" when LC is off - in order to use this options LC must be ON.

In general for faster rendering times you should use IM and LC from file with both engines ON - and with turned "use light cache for glossy rays" and "store direct light" ON.

Are there any attributes specific to the light cache that don't get saved into the Irradiance Map?

LC reconstruction parameters are not saved neither in LC nor in IM - you can use this parameters even when LC is loaded from file.