View Full Version : Lightwave thinking hard post render: Why?

05-23-2007, 01:03 PM
I have a fairly heavy scene. Lots of polys, images. No animation. LW 9.2 Mac. (also does this on my PC at home with LW9.0)

After I hit F9 render, it takes about 20 seconds to render an image of about 1024x768. The image viewer shows the image and it looks good. As soon as i hit 'Continue' LW suddenly has to think about something pretty hard. I get a color wheel or hourglass for the pc. and it sits there thinking for about 30 seconds. Some scenes its more some its less. But that lag is always there. This makes texturing sllooowww.... Even if hide and uncheck render on all the objects but the one i'm texturing..

I realize this is probably just the nature of the beast but.. it bugs me sooo much i just decided to see if i could find out why, then when its happening i can say to myself, well Ben if you wouldn't use textures that big you wouldn't have to wait so long, or maybe.. Ben don't use so damn much geometry on those bolts next time and keep your poly count lower... etc.

Thanks for any information!


05-23-2007, 01:44 PM
I always thought it was releasing / reallocating memory and rebuilding the opengl view.

I may be wrong.

05-23-2007, 02:03 PM
Ya I guess that's what i was thinking too, but really.. I think the stat window says it's using 80mb out of 3GB, why freeze the program to shuffle 80mb. As for refreshing openGL, well it may be but it doesn't seem dependant on what actually is displayed in opengl, i can render with everything hidden and the time delay is still the same.

I took everything out of my scene except the part i was working on and it improved that lag by quite a bit. The program only held up for about 5 seconds which is ok, but to have to edit my scene down to each object i'm currently texturing to get fast feedback stinks. I guess i'm going to have to start using the viper..(the bane of my existance).

05-23-2007, 02:05 PM
You haven't left any post-processing effects on, have you? I forgot I had one enabled, and was wondering the same thing myself for a while...

05-23-2007, 09:27 PM
If your scene requires complex textures, you'll probably want to texture each model in an individual separate scene (under lighting conditions as similar as possible to the final scene) and then merge them together for the final render.

Most professional 3Ders try to avoid processor-cloggingly large scenes whenever possible--one can save a huge amount of time by breaking the job up into the smallest possible pieces.

05-24-2007, 09:34 AM
Tribbles- Nope, not using any effects, i actually tried to load objects from scene into a new scene and the time was the same.

Giacomo99- I probably have 15 images in my scene, some 4096, some 2048, and most 1024 a couple really small. The funny thing is when everything is hidden LW runs great, hell it even runs fine with most stuff visible, i can animate great and move keys, morph stuff, just after i hit render does the waiting happen..

Anyway i guess i was just curious to see if anyone know what exactly it was doing, not a big deal. I'll just break the scene down for render tests.

Thanks for the comments.


05-24-2007, 06:36 PM
I've noticed the same thing on one of my "larger" scenes. Only about 300k polys, and 3 low rez images. I was assuming that it was a problem with my video drivers but I haven't taken the time to investigate.

05-24-2007, 06:58 PM
It does not mean anything that it's showing 80 MB memory used in Render Stats. It's just memory for polygons and points, without any additional memory required during rendering like frame buffer. Press ctrl+alt+del to open Task Manager, switch to Process tab, and in menu Select Columns to show- there are three to turn on: maximum memory used, memory used and virtual memory used (or their equivalents in English WinXP version). Then press F9 and watch especially virtual memory used. Cleaning up virtual memory is especially very heavy task, because usually it must be transfered back to phisical memory (loaded from hard disk), to read pointers to memory and data from it and/or converting floating point image to 32 bit format.

05-24-2007, 09:00 PM
If you look at render window when hitting F9, you'll see LW is setting geometry (first thing that shows up), which usually takes awhile depending on amount of polys and how many are Sub'Dd.

05-25-2007, 10:09 AM
Extent, ya my scene is around 500,000 polys.

Sensei, I see what you mean. Although i'm on a Mac but i found a widget that watches RAM and CPU and stuff and it says
Wired: 255MB
Active: 1.29GB
Inactive: 786MB
Free: 200MB

I looked at my system specs and i should have 2.5GB so that sounds about right. I don't know if inactive means its being used by a program but not accessed but as for the free ram, well when I render it goes down to like 20mb or so. I guess the scene itself is using a ton of RAM even those most things are hidden.

Prospector, the lag that was causing me to pull what hair i have left out was after i hit the continue button after the render is finished. I have accepted all the time it takes before LW even starts to render hehe. I know it has lots to do like subdivide and move geometry and stuff. BTW i love your avatar, i keep watching it to my horror and satisfaction lol.


05-25-2007, 01:47 PM
If you have Subpatch levels set differently for Display and for Render, LW will pause for a long time both before and after rendering. This is the most common cause for lag after hitting 'continue' that I know of. The renderer actually takes the subdivision from OpenGL when the levels are the same, but if they're different, it has to calculate all those subd's at rendertime and dump it afterwards.

Particles can also cause delays like this, especially with wind applied to them.