Terragen 2 crash on negative displacement again...

[jritchie777]

It's not that they don't render correctly - it speeds up the render time.

[Oshyan]

By how much? And have you tried intermediate, safer values, like 1600MB?

- Oshyan

[neuspadrin]

Personally I've never tried over 800 and that was when I tell it to use 8 cores on my i7.  And I run 64bit with 8 gigs ram.

I'll have to make a decently memory intensive scene and try out various memory values when I get home to see if it really plays much of a role. But as Oshyan and I mentioned earlier, even if it does improve speed, you need to find your limits which 2600 is out of the picture, try 800, then 1200, then 1400, 1600, etc to see what is a good balance for speed to not crashing your render.

And as Oshyan mentioned, relying on virtual memory will not help your speeds for sure, virtual memory uses your harddrive.  Thats the worst storage speeds available on the computer.

Which is why I was wondering your computer specs, as if you are relying on virtual memory a lot, then it could be you see speed differences depending on how much actual physical memory terragen was given vs virtual during said renders and not as much of how much you set to be allocated.

[Henry Blewer]

I tend not to change the sub divide cache. Lately, I have been rendering while I am at work. Then I use the clip render to finish the render and combine the images in Corel Paint. For some reason my computer uses the swap memory a lot using Terragen 2. I have not looked into why.
Using a P4 HT, which is now a slow computer, the render time does not matter (much). 1920 x 1080 still can take days to finish a single image.
I also watch TV and movies while rendering, net surf, etc.. So it is probably to my advantage the swap is used. Someday, I'll be getting a new computer just for rendering. This one will be the entertainment and game machine.

[jritchie777]

I've been running subdiv cache at 2048, have been busy with a project once that is done I'll do some actual timings.  To me so far, it has only been judging by eye - which is only my perception of it of course.
Specs:
2.70 gigahertz AMD Athlon II X2 215
256 kilobyte primary memory cache
1024 kilobyte secondary memory cache
Bus Clock: 200 megahertz
BIOS: Phoenix Technologies, LTD 5.49 08/06/2009
3072 Megabytes Installed Memory

Nothing fancy.

Thanks for all the input, soon as I get a chance I'll do a benchmark - I just hope it doesn't ruin the illusion...

JR

[neuspadrin]

So far my test renderings have been showing the reverse.  Dumped a ton of object populations and put it on decent settings, then tried 400, 800, and 1200 settings.  I've seen the higher subdivs take longer in general actually.

Could be my scene I'm testing on just isn't intensive enough but it's A LOT of objects going on.  I think reality is changing the subdiv cache isn't going to make some miracle change in render speed... only a very small fraction if that even.

Still further test probably needed with a variety of scene types. 

[jritchie777]

When ever I deal with water is when I tend to jump up the subdiv cache.

[Oshyan]

It will also depend on how much physical memory you have.

Here are my results with the displacement plane scene in this thread (note that it is a somewhat unusual scene setup so it may be showing a bigger impact than a "normal" scene):

400mb cache: 2 hours 58 minutes 55 seconds
800mb cache: 2 hours 4 minutes 20 seconds
1600mb cache: 1 hour 28 minutes 24 seconds
2400mb cache: crash (out of memory, presumably)

Very interesting results in this case. I shall have to do more tests with other scenes.

- Oshyan

[jritchie777]

Great results.  Better than I came up with.  At least I'm not imagining the render times. 
JR

[jritchie777]

So far this is the type of scenes that seem to benefit by the subdiv cache being higher than 400K.

• Scenes with water, also when I use the water shader as a glass effect on objects.
  
• Darker scenes with high definition of clouds.

I am averaging about 24% to 36% reduction in render times with higher cache values: 1024 thru 2048K.

I haven't seen the code behind the render engine, but obviously in some scenes the higher cache value does indeed help decrease the render time.  I can find no downside to using a higher subdiv cache value (within limits of course and max 2048 for 32-bit Terragen).  Anyone else think of any downside...?

JR

[Oshyan]

The only likely downside is, as you said, running into memory limits. There is unfortunately an inverse relationship between scene complexity and the possible size of the render buffer. My assumption is that more "complex" scenes probably benefit more from larger buffers, but in those cases it is also harder to have large buffers...

- Oshyan

[neuspadrin]

So far this is the type of scenes that seem to benefit by the subdiv cache being higher than 400K.

• Scenes with water, also when I use the water shader as a glass effect on objects.
  
• Darker scenes with high definition of clouds.

I am averaging about 24% to 36% reduction in render times with higher cache values: 1024 thru 2048K.

I haven't seen the code behind the render engine, but obviously in some scenes the higher cache value does indeed help decrease the render time.  I can find no downside to using a higher subdiv cache value (within limits of course and max 2048 for 32-bit Terragen).  Anyone else think of any downside...?

JR

Yep I've been trying water and darker/lower sun settings + heavy cloud use and have noticed some improvements. I think the best choice for this settings is playing it more on the safe side and guessing a slightly lower value -- but to still increase it by a bit.  As if the render crashes its only going to increase the time required .

[jritchie777]

True, but it is easy to figure out.  My desktop is only 3GB memory, after boot up I have about 2.5 GB.  So if I'm only running T2, I can crank it up to the limit of 2048 without fear of a crash.  Task manager/Processes gives a good value of memory being used and what is free.  Stay within the "free memory" limits and no more than 2048 Kb for 32 bit T2.

Question:  Does the 64-bit version of T2 have such limits or has it been optimized for 64-bit OS?

JR

p.s.  Shortcut for Task Mgr (Windows only) Ctrl+Shift+Esc

[Oshyan]

There is no 64 bit version of TG2 yet. And assuming only 500MB of memory needed for everything besides the render cache is not really safe to do in many cases. I reckon you've been rather lucky, or haven't been preallocating that large a cache in every case.

- Oshyan

[jritchie777]

500Mb left for what is not safe?  If T2 is the only thing I'm running...

Or is everyone just intent on discouraging me to shorten my render times???  It's a 'caveat' situation anyway.