Secondary Bounces computed first?

[dlparisi]

As long as we're talking about pre-pass questions (http://www.chaosgroup.com/forum/phpB...ic.php?t=13745) I have a question about the about the secondary bounces. Why does VRay compute the secondary bounces first? Logically it would seem to me that it should compute them after the Primary bounce. Not complaining but this just never made sense to me.

Can someone explain this?

David

[RErender]

Because it works from the camera back to the lights.

[DaForce]

in the case of using QMC or LC for secondary its because its also stored in the IR map when its saved so you would be able to do that if the IR map was calced first.

So the end result would be a saved IR map with the LC or QMC info in it as well.

[tricky]

I am glad somebody else has asked this! I have been using Vray for ages now and have always been too embarassed to ask it!

It is very odd though.

[Da_elf]

ditto

[cpnichols]

A good way to think of it is, the first ray of light from the camera hits the last ray of light on a surface... then it bounces around until it find a light source, which will be the first bounce of light.

[flipside]

The direct light is also calculated after the first bounce

The lightcache actually computes first and secondary bounces, and this first bounce data is used in ir map calculation as a starting point to speed things up (that's how I see it. LC speeds up ir map calculation bigtime so this must be true).