qmc and LC

[Janosik]

hi
got this problem : pc has 12 gb of ram scene after hit render eating cca 4,5 gb of ram but LC calculations doing some presampling ? and cpu usage is too low about 8 % from 16 cores , so why vray cant use all ram and all cpus now after hit render button ?

PS : ram usage rising after hit render very slowly but after hour reach all physicall ram and pc start swapping ....

so why vray dont say on start: you will need more than 12 gb of ram if not, pc will be swap.... hmm ?

[Morbid Angel]

from what i understand you are rendering with displacement, and that is what is being presampled. If its the case then presampling of the displacement is not multithreaded.
To use all available ram you need to allow for it in dynamic memory limit.

[Janosik]

yes you right
but now i rose my amount of phys. ram up to 20 gb and by my opinion simply scene wont render in time , still is problem in slowly memory usage rise and when is LC finally done cpus still dont go at 100 % it s unbelievable for me because is only 2400*1200 resolution , in try res 800*600 was all fine and max ram usage was around 7 gb and now looong looong time of nothing ....

[Morbid Angel]

well this is simply the case of running out of memory. I mean if you render an image at 800x600 with 7gb of ram in use...then the image at 2400*1200 will be about 4-6 times requirement of memory etc. 7*6 = 42 gb of ram you would need in theory to get this one through. I would suggest tweaking your displacement so that it is not so demanding on the poly count.
Perhaps at the higher res you don't need the settings to be as high res as you had on lower resolution, if you are using per pixel displacement.

[Janosik]

it might be like you said but problem is i have 15 cameras in scene BUT problematic are only 3 of them, so other 12 i can render without any problem at 2400*1600 res and never go higher then 9 gb , i am afraid problem is in geometry of some objects ...... in scene is 6 family houses 3 on one and 3 on other side , one street and litlle more 3d trees ( 50 ) and bushes ( 30 ,but all of them , instanced ) and some flowers , displacement got on roof and on bricked fasades. grass is only screen mapped background image ....

so saved file has around 525 mb ...

[Morbid Angel]

i would suggest to use vray proxies as much as possible. With instances they cannot be dynamic so they cannot be flushed from ram, and if you have a lot of objects unique they will garbage up the ram.

[pengo]

A question Morbid Angel my english is not very good so if you could reply more simply as possible.
I'd like to know if u mean that is better to use vrayproxies not copyed or cloned with instance option
Is it better to clone with istance option or not to get dynamic memory works better?
thanks in advance

[3DMK]

If you are using displacement with 'View Dependent' then this is the likely cause of your problems.
View Dependent works off a certain pixel size [default 4 px] so if your renders have doubled in size then your displacement is subdividing 4 times as much.

If you render at say 800x600 and your displacement works fine at 4px subdivisions size and you suddenly render at 1400x1200 you can change your subdivisions size to 16px and will get the same result.

The only way to have your displacement use the same ram no matter what size your render is , is to change the sampling size to world scale, although this is not a good idea for large areas as it will kill your ram pretty quick.

Hope this helps

[Morbid Angel]

for instances this is how it works:

if you create an object that is then instanced, that single object is loaded into ram. If you create 10 objects which are unique and instance those 10 objects, 10 objects will be loaded into ram. Once loaded into ram they will not be flushed.

if you create a single proxy and instance that proxy, that single proxy will be loaded into ram.
if you create 10 proxies which are unique and instance those 10, all of them will be loaded into ram. The difference is that proxies can be flushed during rendering and instances cannot be.

[pengo]

Thanks Morbid Angel

[werticus]

you could also render stripes through back burner to save ram.

[Janosik]

hello

well i try all of your opinions but no change

today i was debug a scene and found nice discovering , on two family houses was roof displace really bad and that caused this weirdness with LC and ram usage so i rid off vray displace modifier and did it like from old school , subdivided plane and aply max displace modifier and all is good now , dont know why vray displace modifier failed ( to be sure i isolate only planes with vray 2d displace and hit render thats why i found this bug )

so for now i happy , i ll see what s will happen next time to me in CG court