glass rendering slower [ SOLVED ]

[zarti]

hi everyone ,

im in a situation where i have prepared to export buffers of a glass material separately to later have maximum control in compositing process .. i did this also in order to spare as much time as possible in rendering . ( Micropoly , H11, b.1.229, WIN7_x64 )

what i cant explain is the fact that the first frame starts and render in very acceptable times for me , while any other frame but the first one renders many .. but Many times slower . indeed it starts so slow that i accidentally discovered it was rendering( had a phone call =) ) . when i came back i noticed the first completed buckets ( ! ) .

i believe there is nothing changing between frames in shading context and im simply rotating the object just to see its appearance under different POVs .

based on your experience( if you had one like this ), what could be causing this ??

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any help or hint wd be greatly appreciated .

!thanks

EDIT ::

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the original name of this topic was "render slower on frames different from 1 ( ?? )" .

i updated it in order to make more sense , more 'visible' and maybe help quickly someone in future ..

sorry .. and hope this editing isnt breaking any rule =)

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Edited May 11, 2012 by zarti

[michael]

can you provide an example file?

[zarti]

i just found what was it .. > Many overlaping primitives . not so many .. =)

shame on me , but i can justify my self a bit by saying that the geometry was modeled and exported from a NURBS modelling app .

also , its polycount was high , so i didnt suspected at that .

also the orientation of faces towards the camera where rays were bouncing was minimal on the first frame . hence the fast rendering of it .

to be fair toward the First Frame and thank it =) that helped rising my doubts a lot and posting this topic .

the comparison wdnt be possible without you , first Frame , and electricity bill will be lighter this month .. =)

,

anyway im trying to make this topic( maybe )useful for someone else in the days to come :

if you suspect sometimes that Glass is rendering ' more than what you wd expect ' .. throw a Clean SOP and see what it cleans .

also be careful with Foreach SOPs( when you arent creating extra geometry within those )by comparing the quantity of geometry coming in and out from those .

in my case i didnt investigated up the nodal flow on Foreach SOPs i used to elaborate that model , but just a warning ..

thank you Michael for your reply !

Edited May 11, 2012 by zarti