DR & prepass

[timmatron]

So why is it that when you use DR it only does 1 prepass and and when DR is off it goes through the regular amount of prepasses? It seems to be computing just as much either way, because the single pass on DR goes slower than the 1st pass without DR.

Not that I mind. In fact it would be nice to always have only 1 pass for everything, even when not using DR.

[tom schuelke]

i think

this is because it would be difficult to transfer the result of each prepass a bucket on a slave would render to the next computer that would go on at that point.

it just reduces network transfer and now one computer does all prepasses for on bucket in one step.

sounds logical to me.

Tom

[timmatron]

Yeah that makes sense to me too. I wonder if it takes more time for Vray to do multi-passes too, for the same reason. Wouldn't just one pass for everything save a little more time?

[egz]

If you look closely you'll see that each bucket actually does more than one pass. It's just divided into buckets instead of single frames. This is a lot faster than distributing the first pass, syncing the result, distributing the result, doing the second pass, syncing the result, distributing the result, doing the third pass etc. Now it just does all the passes inside a bucket, then it syncs it all in the end.

[vlado]

Re: DR & prepass

In fact it would be nice to always have only 1 pass for everything, even when not using DR.

Uncheck the "Multipass" option in the irradiance map settings.

Doing things in passes has the advantage that each pass uses the result from previous passes and the samples are better distributed. When things are done in a single pass, there is less information available and some samples may end up being aligned on the boundaries of the buckets. Both methods seem to take about the same amount of time anyways.

Best regards,
Vlado

[timmatron]

Awesome! Thanks so much for the helpful info!