Batch Render progressively slows down

[ignuf]

Hi,
ok I have PC 8 core (win7) and a macbookPro (quad core hyper-threaded - so 8 core) acting as a slave, I'm rendering a very simple maya scene which in VFB takes bout 30 sec to render, its a simple product moving around the screen, the product doesn't leave the shot and no more geometry is added to the shot through the animation.

indirect illumination I'm using Irradiance map for primary (set to med animation setting) and light cache for secondary (set on single frame with use light cache for glossy rays)

I set off a batch render and the scene takes about 30 sec per frame initially but after 300 or so frames the render progress slows down to 1 frame every 3 mins... if I cancel the batch render and then start it again at the last frame that was rendered the batch starts rendering 30 sec per frame and then slows down again over time.

Any suggestions as to why this would be happening ?


thanks for any help

[vlado]

If you look at the V-Ray log, which part of the rendering increases the render time?

Best regards,
Vlado

[ignuf]

Hi Vlado,
thanks for your reply,

it looks like the pause between the prepass and the actual rendering initially its about 20sec then as time goes on it grows to roughly 2 to 2.5 mins. (thats after about 700 frames)

thanks
Guy

[vlado]

Ok then; what's the mode for the irradiance map (incremental add, single frame etc)?

Best regards,
Vlado

[ignuf]

its on multi-frame incremental

best regards
Guy

[vlado]

Ok, then this is probably why it's slowing down; as new information is added to the irradiance map, it takes longer to prepare the map for rendering. It might be worth trying to pre-render the irradiance map e.g. every 10th frame, and then render with the saved map.

Best regards,
Vlado

[ignuf]

ok i'll try that .

thanks for your time Vlado !

best regards
Guy