Dynamic Memory Limit (again)

[zeronove]

I'm dealing with an extra large image (18k wide) every is running fine but rendertimes are a bit high

...trying to optimize it I'm looking into the Dynamic Memory Limit but after a long posts reading I'm still confused:

- which are the main guidelines to set up this value?
- the amount of ram to set has to be understood for each thread, core, cpu, pc or whatever? I mean, the default is 400mb (that sounds low), does it mean that on an i7 with 4Gb pc it stays for 3.2 gb? (400x or does it mean 400Mb in total so it's better to raise it up towards 3Gb?

thanks in advance

[Morbid Angel]

I am not sure if its per thread, probably not. But usually I would allocate as much ram to the render as the machine has, more ram faster rendering of dynamic geometries.

[zeronove]

I see, so it means more or less 4k on a 4Gb pc
as far as you know does it help even if I've only static geometry?

This time my scene is quite simple and my problem is only with hi res; from my previous tests with normal res (2500 wide) I had 1 hour render time so for an image that is 20000 wide I was expecting a 16x rendertime but the actual estimate is now 36 h!!!
The strange thing is that with lower res, let's say 15000 wide, the rendertime were as expected!! ...so, maybe something happend going from 15000 to 20000, that's why I'm looking into the memory thing

[Morbid Angel]

static geometry has no effect on this setting. It will always be loaded into memory.
Are you rendering to .vrimage? maybe changing bitmap pager settings will improve your render time.
As far as the math goes I'm not the best at it, but I think every time you double the res of an image its quadruple the render time. So lets say you have 2500 at 1 hour, 20000/2500 is 8 times the size, so 8 x 4 is 32 hours...your estimator is pretty close.

I also just spoke with a friend and he added that it will also depend on the filter of the image. For example if you have larger area of similar color it will be filtered and sampled faster then an area with small details like grass for example.

[vlado]

- which are the main guidelines to set up this value?

If you use lots of displacements or proxies, it makes sense to increase this value. If it is too low, V-Ray will also print a warning about this. You will have to experiment to find the right value, but generally set this as high as possible.

- the amount of ram to set has to be understood for each thread, core, cpu, pc or whatever?

The value is for the entire rendering, regardless of how many threads/cores/cpus take part in it.

Best regards,
Vlado

[zeronove]

thanks for your answers

but generally set this as high as possible.

as possible depends from the amount of ram installed? so for 4Gb could make sense raising it to 3200mb?

Are you rendering to .vrimage?

absolutely yes, as Vlado usually says "it always works"

maybe changing bitmap pager settings will improve your render time.

that's one of the changing from my test file, first was on now it is switched off

As far as the math goes I'm not the best at it, but I think every time you double the res of an image its quadruple the render time. So lets say you have 2500 at 1 hour, 20000/2500 is 8 times the size, so 8 x 4 is 32 hours...your estimator is pretty close.

I probably figured out what's going on...
I usually evaluate rendertimes the same way but this time I've made some stupid mistakes: 2500 pix wide takes 1 hour then 20000 pix wide has to take 8 hour but that result has to be multiplied for the other direction 8 times as well so 64 hours as rendertime have to be expected!!! hopefully, following some last minutes optimization, they drop down to 36 hours

I also just spoke with a friend and he added that it will also depend on the filter of the image. For example if you have larger area of similar color it will be filtered and sampled faster then an area with small details like grass for example.

if you are talking about aa filter in my case they are off

Said that I'm now hoping the 36 hours estime is correct because I just realized that I forgot the BB timeout to 40 hours

crossing my fingers