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View Full Version : Help understanding hou the LW 9 Render engine 'thinks'.



ssutherland
09-04-2006, 08:49 PM
Okay, so I know it does not really think, but this render engine seems very different in the way it assesses a scene and renders it. I have used Imagine extensively and TrueSpace for a while, and they typically render from the top down, line by line (except with a dual processor, where TS has each processor render segments of horizontal lines). LW appears to render individual objects, or segments of objects, ALMOST like it is rendering from the back of the scene to the front, or something similar.

This process appears to add a signficant amount of render time. With my dual core Athlon, 2.2 GHz per core (if I recall correctly), and 2 Gb of RAM, I expect many renders to be practically real time. I used to run Tornado 3D on my Amiga with a simple PPC processor and I could practically render complex animations 2-5 frames per second at 768x480 resolution.

A particular example is the Microwave scene that comes with LW 9, under the folder Lighting. Now, I don't know exactly how this scene is set up (haven't figured out how to manipulate my way around scenes yet), but I rendered this on my system at the default 640x480 and it took 31 minutes!! I have not seen rendering times that slow since my Amiga 3000 days. I assume that it is something in the setup for that scene (high antialiasing, area lights, or something) that makes it so slow.

And what is the deal with 'passes'? I see some scenes with 1 pass, others, like the classic microphones one (don't recall the name exactly) have 17 passes. What is LW doing on these passes? I rendered a speaker scene and the little preview shows what each pass is doing and it LOOKS like it is redoing the scene the exact same way each time. Now, I don't see motion blur on this image, which would be a possible explanation for 9 passes.
Can someone take a crack at explaining what passes are and why I need them?

So far the renders look very nice. Unfortunately, I have yet to find out how to change the render resolution. I thought I had found it in a drop down selector, but then when I hit render frame, it defaulted to the scene default, in this case 640x480.

Still feeling my way around the UI. Sorry if all of this has been asked before. I REALLY want to like this program, but I have gotten so used to fast renders that I am not totally on board..yet.

Scott
Haverhill, MA

SP00
09-04-2006, 08:58 PM
There really is a lot to explain here and it is best to go thru some of the tutorials on the NT website. There are many ways to cut down render times without sacrificing too much image quality. The type of Radiosity is one of them. You might want to look that up in the reference book to give you some ideas. Also there are 2 places to change resolution, global settings and the camera properties. If you want to change it directly in camera properties, make sure globals are not checked, otherwise, it will use the global values. The passes are probably antialiasing settings, so you can turn that down if needs be. Like I said, there is a lot to cover, so go thru a tutorial on NT website on rendering to help you out. Have fun :)

manholoz
09-04-2006, 10:53 PM
Also a newbie here, but as a newbie I can tell you that some things that look very similar imply radically different render times. For example, I am building a fog effect creeping down a pyramid, using hypervoxels.
If I used true volumetrics, it would probably finish rendering in time for the christmas turkey. So I opted for sprites, which granted, are not so super-real, but quite adequate for what I am doing in my scene.

If you think 30 minutes for a render is a lot, you probably have never used montecarlo radiosity (in any render engine) or stuff like that. Just google around for render times with Maxwell renderer (which can be linked to lightwave via a plugin). They can take days on a single frame.

I think 30 minutes for a reasonably detailed scene is in fact quite fast. The scene I am rendering at 1280x1024, with 7 passes, in 2 segments, will take 5 hours in total (according to Lightwave's render screen). And I don't find that too slow. I rendered a house in Maxwell in the weekend, and it took 23 hours to get the amount of detail I needed.

Anyway, regarding rendering in old computers, I rendered a classical Mandelbrot set in the Commodore64 and it took 13 hours. And THAT was 2D! I think now most Mandelbrot sets like those render in near-realtime.

*Pete*
09-05-2006, 02:17 AM
The passes you mentioned are doing anti-aliasing, it means that it re-renders every pixel with every new pass it does.

ill try to explain it more in detail now, but im not an expert.

a polygon is infinetely thin, thinner than a pixel. so a pixel can for example end up having 1/4 of it covered by a white polygon and 3/4 covered by a black polygon.

without passes, or AA, Lightwave would render that pixel as 100% black, instead of 75 % (3/4) black, as it should be.

now, if you use 2 passes on that pixel, Lightwave will notice the white polygon in it also, now rendering the same pixel but this time at 50 % black (or medium grey), but this is also slightly wrong.

with 4 passes, you should end up with the pixel end up at 75% black (or dark grey), it would look more correct and you would have a harder time to see any jagged edges.

now, it doesnt only deal with black and white, you could have any color mixing the same way, as for example red and blue, ending up with a pixel with 75% red and 25% blue.

it, it a way gives you better looking images, there is naturally a point where it doesnt improve your picture any more visually, so use with care.

the reason, as i understand it, why passes were used in that scene, was to make a clearer, better image without jagged edges...all 3d software does the same to my understanding.

Snosrap
09-05-2006, 08:33 AM
I have used Imagine extensively and TrueSpace for a while, and they typically render from the top down

Boy that brings back memories! I do remember the first time I saw LW (Inspire) render and thought wow that's different. However, that very first render with Inspire was 30 fold better than anything I could do with Imagine or Caligari24 (remember that one, TrueSpaces’ little brother) LW9 has a new camera like neverko mentions, that renders from top to bottom. You should probably look at the FPrime plugin for LW if rendering speed is an issue. I hardly ever use LW’s renderer anymore.

Cheers
Snos

manholoz
09-05-2006, 09:01 AM
Pity FPrime does not recognize nodes, node setup for materials is absolutely fantastic

ssutherland
09-06-2006, 05:52 PM
Okay, I'll bite. How do I change the camera used for rendering to this exclusive raytracing camera that will 'boost my render speeds' for heavily raytraced scenes and will render the 'normal' :) :) way?

Thanks for the advice. BTW, is FPrime shareware, freeware, or a commercial program?

Scott
Haverhill, MA

BTW, my replacement dongle is on the way, so goodbye to RNBO[30]=1 error messages (and [31] and [32]), or so they tell me at 'NewTech' support. Time will tell.

Bog
09-06-2006, 05:56 PM
Select your Camera, hit "p" for properties and in the dropdown in the top right of the panel, switch from "Classic Camera" to "Perspective Camera"

Snosrap
09-06-2006, 07:49 PM
BTW, is FPrime shareware, freeware, or a commercial program?




Commercial. $399. With the recent price reduction on Lightwave from $1495 to $795, it makes FPrime seem rather pricey. I bought it when it first came out @ $279 which was way worth it. Actually, if you would ever start to make any money with LW, FPrime would be one of the first plugins one should buy. However after training 4 new users over the last year I can attest to the fact that it speeds up learning LW layout and rendering considerably.

Cheers
Snos

toby
09-06-2006, 11:25 PM
Read the manual dude!

If you really want to know how to use this software you've got to spend a couple hours reading - especially if you want to learn how LW 'thinks' - that's exactly what the reading the manual will help you with. I know it's not nearly as exciting as playing with LW, but if you're excited about 3D it is an exciting read. And you'll learn things in a few hours that you would never even think to ask here. I'd never even heard of a clip map until I read the manual.

And don't worry about the "normal" way of rendering, sometimes it's slower. Worry about the result instead of the method! I just checked that microwave scene, it had some settings that were much too high. After correcting it, it rendered in one minute.

loki74
09-07-2006, 12:31 AM
Well, I've never actually sat down and read the manual. But if something stumps me, I'll go in and look it up. If I cant find it, then I bring it here...

As toby pointed out, the "normal" way is not always better--the classic camera does have its place!

The classic camera works well in scenes where you have minimal polygon count, and there is no need for DOF through transparent objects or in reflections. In these cases, the classic camera may perform better than the new one. This is because the optimizations the new one makes take up time--if the time saved from the optimization is a lot (that is, in the case of a high complexity scene), then the render can be extremely fast by comparison. But if not, the optimization is wasted effort, and the render is slower. Therfore, classic camera will be faster in that situation.

The way I see it, both cameras are tools, each with its own purpose. I wouldn't like LW9 to ditch the old renderer any more that I would like it to ditch SubPatches, keeping options open is good (and I think most here would agree). You shouldn't immediately reject something because it is unfamiliar... and either way, its the final image that counts.

Good luck with LW!

ssutherland
09-07-2006, 07:51 PM
Read the manual dude!

I read manuals cover to cover. I am anal that way. Unfortunately, I work for a living (don't we all) and my living is designing field-portable narcotics, explosives, and chemical analyzers, not 3D animation (a hobby), so I get to read them at lunch and on bio breaks:beerchug: . This manual is, in all its glory almost 1500 pages in total. That is a lot of bio breaks!! And I thought the TS 7 manual, which weighs in at just under 1000 pages, was thick. Then I have to try the stuff on the computer... I'll get through the manuals, but when someone waves a dog biscuit in front of me (like faster raytrace renders), I jump and bite.

My new dongle arrives tomorrow, so I hope I can actually run Modeller after I get it. Then watch out...:)

Scott
Haverhill, MA

toby
09-07-2006, 08:19 PM
I read manuals cover to cover. Then I have to try the stuff on the computer... I'll get through the manuals, but when someone waves a dog biscuit in front of me (like faster raytrace renders), I jump and bite.

Excellent! Pop quiz in two days, be ready :) You'll be ahead of the curve very soon. And by all means take breaks when you get a biscuit, you can't memorize it all anyway - but it does give you a very good sense of how LW works, so you'll be able to figure things out with a minimum of frustration.

And before I forget again, welcome to the cult!

:bowdown:
:lwicon: :bowdown:
:bowdown:

nthused
09-07-2006, 08:33 PM
If you want to pick up the pace in learning the LW9 - pick up Dan Ablan's video series. (I think Larry Shultz has some DVDs out too.)

Well worth the money in the frustration they'll save. And of course learning the right way the first time is so much easier than having to unlearn before learning...if you know what I mean.

lede
09-08-2006, 09:03 AM
There are a lot of people around here just like you in the way it is only a hobby and a dream. Just take the time to read adn you'll be answering these questions for new users in a few short years.

There is a lot to learn about LightWave so take your time and don't get to impatient. There is a lot you need to learn so take your time and take it in small doses. I've been using LW for way to long to count anymore and even to this day I am still learning how to use the software.

Oh and welcome to the group hope to see you in the WIP section soon.

-Lee

ssutherland
09-08-2006, 07:59 PM
[b] I just checked that microwave scene, it had some settings that were much too high. After correcting it, it rendered in one minute.

For my edification and learning, can you enlighten me as to what settings were too high, why, and what you changed them to? It would help me to ID some of the settings in LW that consume lots of render cycles.

Thanks,

Scott
Haverhill, MA

Go Gators!

toby
09-08-2006, 09:11 PM
Of course!
There were two things: there's an area light in the scene with it's quality set to 4, which is the default, and 3 is usually enough. Lower quality is grainy compared to higher quality, but anti-aliasing reduces graininess, so the more AA you have the lower your setting can be, saving you time with no loss in quality. Funny thing is, the light was only set to 4% intensity, it could be turned off with very little change in the image.

The second and biggest time saver was reducing the ray recursion, in the Render Options panel. This is how many bounces (or passes through transparency) a ray makes before it stops calculating. Default, and this scene, is 16, but I've never seen a scene that actually needed 16, I always end up somewhere between 2 and 11. If it's too low, what you'll see is reflective or transparent surfaces turning black or a loss of detail, refractive sufraces getting cloudy, or shadows not going through transparency. The key is to do test renders to find the minumum that you need.