One Render Fast Next One Slow

Rev3D

Hello, 

I am rendering a sequence of images and in the scene one render will take 30 minutes to complete then the next could take 30 minutes to do 5% even if I don't change anything and render from the same camera. Running Daz 4.22.0.16, I have CUDA 0 selected in advanced, my system in a 4090 with 64gb's of ram and a Ryzen 9 7900. 

TimberWolf

VRAM. You've run out of it. Studio or Iray (not sure which) doesn't release the VRAM on the GPU completely between renders and it caches materials.. If you render one complex scene after another without restarting Studio you will eventually (or, in your case, the second render!)  excede the available VRAM, even on a 4090 and the render will run entirely on your CPU. This is why your render times increase massively. We've had this happen with a pair of 48GB A6000s...

You can check this easily enough in Windows Task Manager - have a look at your GPU's temperature; it will have dropped back to roughly idle values. Your CPU cores will be running at 100%. GPU-Z will tell you *exactly* what's going on with the GPU, but the task manager is enough to figure out that this is happening.

Restart Studio between renders, especially if they're nudging up against your VRAM limit in the first place. A mild annoyance, but it will cure the problem.

If you are rendering a series of images for a game/visual novel et.al then you could try something like ManFriday's Render Queue which has the option to restart automatically inbetween each scene in the queue. We use it all the time for animations and final scene rendering - worth every cent in my opinion.

https://www.daz3d.com/render-queue

 

Rev3D

TimberWolf said:

VRAM. You've run out of it. Studio or Iray (not sure which) doesn't release the VRAM on the GPU completely between renders and it caches materials.. If you render one complex scene after another without restarting Studio you will eventually (or, in your case, the second render!)  excede the available VRAM, even on a 4090 and the render will run entirely on your CPU. This is why your render times increase massively. We've had this happen with a pair of 48GB A6000s...

You can check this easily enough in Windows Task Manager - have a look at your GPU's temperature; it will have dropped back to roughly idle values. Your CPU cores will be running at 100%. GPU-Z will tell you *exactly* what's going on with the GPU, but the task manager is enough to figure out that this is happening.

Restart Studio between renders, especially if they're nudging up against your VRAM limit in the first place. A mild annoyance, but it will cure the problem.

If you are rendering a series of images for a game/visual novel et.al then you could try something like ManFriday's Render Queue which has the option to restart automatically inbetween each scene in the queue. We use it all the time for animations and final scene rendering - worth every cent in my opinion.

https://www.daz3d.com/render-queue

 

That is very interesting to know thank you, is the amount of items I have in the scene causing this to happen? This is the first time this has happened to me from one render to another. Is it the amount of lights I have in the scene? Or an accumulation of everything. 

I shall certainly look into getting this product you recommended.  

Weird.AL.Einstein

TimberWolf said:

VRAM. You've run out of it. Studio or Iray (not sure which) doesn't release the VRAM on the GPU completely between renders and it caches materials.. If you render one complex scene after another without restarting Studio you will eventually (or, in your case, the second render!)  excede the available VRAM, even on a 4090 and the render will run entirely on your CPU. This is why your render times increase massively. We've had this happen with a pair of 48GB A6000s...

You can check this easily enough in Windows Task Manager - have a look at your GPU's temperature; it will have dropped back to roughly idle values. Your CPU cores will be running at 100%. GPU-Z will tell you *exactly* what's going on with the GPU, but the task manager is enough to figure out that this is happening.

Restart Studio between renders, especially if they're nudging up against your VRAM limit in the first place. A mild annoyance, but it will cure the problem.

If you are rendering a series of images for a game/visual novel et.al then you could try something like ManFriday's Render Queue which has the option to restart automatically inbetween each scene in the queue. We use it all the time for animations and final scene rendering - worth every cent in my opinion.

https://www.daz3d.com/render-queue

 

All true, but...I've seen the second or third render slow down considerably even when it's using the GPU according to Task Manager. Also, the last time I tried Renderque it was unable to render the hair properly, even when I checked "force tesselated hair"...