0% on second GPU investigate and ask for help.

[ghiom3d]

Hello,

I have a Big laptop with 2 GTX 1080 and a I7 8700K for rendering.
And 64go RAM is enought for what i rendering.

My issue is that only 1 GPU seems to rendering, even if Vray is setup to use the 2 GPU.


To try to solve this, i have installed the lastest Nvidia drivers.
I've check that Sli is not checked in nvidia config.

Then i have try with only 1 GPU at time on a selected part of the picture.

GPU 0 alone without CPU : 58% 1 mn 02 sec
GPU 1 alone without CPU : 06% 0 mn 57 sec
CPU 4.3Ghz without GPU : 100% 5 mn 54 sec

GPU 0 is the one with screen on it. that's must be why it's a little slower.
So, ok even it's say 06 % GPU 1 seems to render.

I continu my investigate :
GPU 0 + GPU 1 : 40% / 0% = 0 mn 45 sec . I'm a little disapointed, i was hoping something like 35- 38 sec . But many things can be in game here .. so i will add the CPU maybe i will gain 2 sec more.
All GPUs and CPU = 0 mn 43 sec.

SO .. I really need to render faster, this is only a little part of my rendering.
I try Brute force GI engine instead of lightcache, because my scene is just a perfume bottle, there is near only reflections and refractions.
All GPU + CPU = 0mn 41 sec. the rendered picture is the same as previous. great , 2 sec more saved on this part of the picture.


Now, i can try to change adaptative lights by other options.
Uniform probabilistic : 0mn 36 sec !! damn that's a big difference !
Full Light optimisation : 0 mn 37 sec .ok, so adaptative seems not the better choice for this raytracing scene.

uniform probabilistic 4 instead of 8 : 0mn 39 sec .. bad ..
uniform probabilistic 16 instead of 8 : 0mn 38 sec . bad too.

I know Bucket size can help me to reduce rendertime in my case. but i don't find where to change it in GPU NEXT ..

Any idea how to reduce rendertime with GPU next ?

thanks for your help, i hope this little story will be helpfull for some new user

[matanov]

Hi Guillaume,

For monitoring GPU utilization try using some 3rd party application like MSI AfterBurner or EVGA Precision. If you want to stick to the Task Manager, you should switch the mode from 3D (above the GPU graph in your screenshot) to Compute.

About the render times - for a scene like yours (just a single object and most of the image to be background), the scaling with multiple GPU's won't be great (as you already found out).