Render resolution and Iray VRAM usage

r0bertas

Does render resolution impact VRAM usage on Iray ?
I have a scene with a G8F and a very simple environment. It does fit on a GTX970 4GB when rendering at 1080px by 1080px, but if I increase resolution to 2160px by 2160px I'm out of VRAM.
I always thought that resolution only impacts render time ? Have you noticed identical issue ?

OZ-84

Its new to me that resolution has an impact on vram usage. Never observed something like that. 

r0bertas

OZ-84 said:

Its new to me that resolution has an impact on vram usage. Never observed something like that. 

Well this is why I'm asking, not sure if it's really the case :) The whole vram usage seems very unpredictable to me. More than once I couldn't fit a scene into VRAM one day, and then without any modifications it fits the other day, this only happens when it is on the edge of VRAM limit of course, but still 

And yes I always try to restart DAZ and even reboot my machine.

OZ-84

r0bertas said:

OZ-84 said:

Its new to me that resolution has an impact on vram usage. Never observed something like that. 

Well this is why I'm asking, not sure if it's really the case :) The whole vram usage seems very unpredictable to me. More than once I couldn't fit a scene into VRAM one day, and then without any modifications it fits the other day, this only happens when it is on the edge of VRAM limit of course, but still 

And yes I always try to restart DAZ and even reboot my machine.

It always depends how much memory Windows reserves for itself. There are various tools avaiable to check the GFX ram usage. You should take a look :-)

r0bertas

OZ-84 said:

r0bertas said:

OZ-84 said:

Its new to me that resolution has an impact on vram usage. Never observed something like that. 

Well this is why I'm asking, not sure if it's really the case :) The whole vram usage seems very unpredictable to me. More than once I couldn't fit a scene into VRAM one day, and then without any modifications it fits the other day, this only happens when it is on the edge of VRAM limit of course, but still 

And yes I always try to restart DAZ and even reboot my machine.

It always depends how much memory Windows reserves for itself. There are various tools avaiable to check the GFX ram usage. You should take a look :-)

Yeah, should have noted that I render on a separate card, i.e. it is not used by Windows.
And I do use GPU-Z to monitor usage ;)

Would appreciate if more people would share their experiences with regards to resolution and VRAM usage.

Daywalker Designs

r0bertas said:

OZ-84 said:

r0bertas said:

OZ-84 said:

Its new to me that resolution has an impact on vram usage. Never observed something like that. 

Well this is why I'm asking, not sure if it's really the case :) The whole vram usage seems very unpredictable to me. More than once I couldn't fit a scene into VRAM one day, and then without any modifications it fits the other day, this only happens when it is on the edge of VRAM limit of course, but still 

And yes I always try to restart DAZ and even reboot my machine.

It always depends how much memory Windows reserves for itself. There are various tools avaiable to check the GFX ram usage. You should take a look :-)

Yeah, should have noted that I render on a separate card, i.e. it is not used by Windows.
And I do use GPU-Z to monitor usage ;)

Would appreciate if more people would share their experiences with regards to resolution and VRAM usage.

What version of Windows? There is a known issue with Windows 10 reserving VRAM on every card that might possibly have a monitor connected to it at some point, even if you never plan to do so.

r0bertas

daywalker03 said:

r0bertas said:

OZ-84 said:

r0bertas said:

OZ-84 said:

Its new to me that resolution has an impact on vram usage. Never observed something like that. 

Well this is why I'm asking, not sure if it's really the case :) The whole vram usage seems very unpredictable to me. More than once I couldn't fit a scene into VRAM one day, and then without any modifications it fits the other day, this only happens when it is on the edge of VRAM limit of course, but still 

And yes I always try to restart DAZ and even reboot my machine.

It always depends how much memory Windows reserves for itself. There are various tools avaiable to check the GFX ram usage. You should take a look :-)

Yeah, should have noted that I render on a separate card, i.e. it is not used by Windows.
And I do use GPU-Z to monitor usage ;)

Would appreciate if more people would share their experiences with regards to resolution and VRAM usage.

What version of Windows? There is a known issue with Windows 10 reserving VRAM on every card that might possibly have a monitor connected to it at some point, even if you never plan to do so.

Windows 7 Ultimate Service Pack 1,
lookint at GPU-Z - I don't think OS takes any VRAM, If I close and reopen DAZ it shows 0 MB on both dedicated and dynamic usages.

rames44

As I recall, the log file includes lines that reference allocating a “render buffer.” This might be resolution-dependent. Might be worth looking at what it says for a smaller and larger resolution render.

r0bertas

rames44 said:

As I recall, the log file includes lines that reference allocating a “render buffer.” This might be resolution-dependent. Might be worth looking at what it says for a smaller and larger resolution render.

Thanks for the idea, will get log file for renders in both resolutions and will compare.

Padone

Definitely yes. The larger the final image the more vram iray needs. This is because iray allocates a frame buffer for the whole picture. Also the minimum required working space will increase accordingly.

 

EDIT: There are other PBR engines that are tile-based. So they only allocate a frame buffer and working space for a few tiles. And in this case the needed vram is independent from the final resolution. For example Cycles works this way.