QUESTION: Rendering Large Assemblies in PhotoWorks

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TOP

I know there are a lot of people who render parts or relatively small
assemblies. What about multi-thousand part assemblies? Exploded views
of assemblies with a few hundred parts?
 
We render assemblies of approx. 1000 parts or less. We don't really have
any issues, once in a while we may see a memory problem (we run a gig of
memory in our current systems). If that occurs it can usually be solved by
suppressing components in the assembly that won't be seen in the rendering.
 
What kind of rendering times do you see?

How compact are your assemblies? What I mean is, if you did a UPS
length measurement on the largest and smallest part and divided one
into the other, what range would that ratio be in?

UPS length is the sum of the length, width and height of a package.
 
I'm sure that YMMV. hehe. (Your mileage may vary).

What I mean is, that you shouldn't have much of a problem rendering the
assembly in a rather "basic" mode (limited materials, no shadows,
refractions, reflections, etc.). Of course, you'll see some seriously
increased rendering times whenever you start to "crank up" the level of
detail that you want to see. I'd say that you'll want to get your basic
materials, lighting, scene, etc. set up first, then start to turn up
the "fancy stuff" (reflective environments, refractions, anti-alaising,
etc.).

I can render fairly complex assemblies in a matter of minutes (or
seconds) at a basic level, but to counterpoint that, I have single
parts that took hours to render with what I would consider to be
"photorealistic" results.
 
Let's say brochure quality. At a minimum colors assigned to everything
visible, shadows are not necessary, several directional lights. The
other thing is that the largest part is a roughly a 100ft hemisphere
and the smallest would be on the order of a 1/4-20 bolt.
 
Well our largest parts are probably 20' x 40' and the smallest would also be
a 1/4-20 bolt. Fye is correct, rendering time is a result of a number of
different settings, options and save options as well has the computing
hardware your system has. You talk about brochure quality, this is going to
require the use of some advanced PW features and these will have a great
impact on rendering time. Some materials take longer than others to render
convincingly (transparent and reflective).Without actually setting up some
test renders with your assemblies this is a very hard question to answer. I
can tell you our typical (brochure quality) rendering will take somewhere
between 1 and 2 hours on midgrade DELL workstations. I expect that to
change once we upgrade to dual core chips. I wish I could give you a more
concrete answer.
 
Thanks. We won't need transparency or reflective. I'll give it another
shot.
 
What about NOT using photoworks then? how about just simply using
Realview graphics and lighting the assembly up using SW lighting?
You'd only have to apply materials to the components that were large
enough to justify it anyway... would be a quick method at least.

Can you take a screenshot of the overall assembly and post/e-mail it?
Would be interesting to see what you're up against.
 
You could take out the parts that are going to be small/invisible. Hide
all inconsequential fasteners and use simplified parts for parts of the
assy that will be far away from the user. I have saved assys as part
files with only the external faces saved (this is an option for saving
out of the assembly). That means less polygons to calculate for, but it
means a bit of a wait while Solidworks calculates the removal of inner
faces. The parts are then dumb surfaces that don't rebuild- which is
fine when you are rendering a finished product.

Keep it Simple: If you are using Spotlights, use only 2-3 spotlights.
Set only one of them (referred to as the key light) to cast shadows.
This reduces the complexity of calculations. The second is a fill light
and only used to reduce the dark shadow bring out detail in the dark
areas. This fill light is arranged roughly diametrically opposed to
the key light. The third light is called a rim light and is typically
used to "pop" the rendered object from the background. It is above and
behind the assy (optional really- it might not look believable for
really large objects). Use large cone angles to cover the while model.
Tell us how it goes.

Use the Scene Room to good effect, Align the model with the floor and
use a good material.
 
....snip
Use the Scene Room to good effect, Align the model with the floor and
use a good material.
Click to expand...

I would like to have a grass or gravel effect for the floor. The
background could be sky or a neutral color as it may have to be removed
for the brochure.

The simplifying has been done to some extent, somebody else's model is
being used for now.
 
If your going to remove the background at some point keep it "white" and
save the file as a .png. This will set the background to transparent by
default and make it easier to add a background in a photo editor.
 
That's a good tip. I've been making the background some ridiculous shade
of yellow or green that doesn't show up anywhere else in the rendering
and setting it transparent in Irfan. White w/ png will be much better
as long as highlighted shiny areas don't also become transparent.
 
Just a comment about lighting and rendering times.

Correct me if I'm wrong here, but it seems like the item that has the
largest impact on rendering times is the quality of the shadows and/or
fog for your specific lights.

That's just my latest observations, so I could be wrong about this.
 
I would say your absolutely correct, pertaining to lighting anyway.
 
Rob - I know you're big on PW, so you might be interested in a macro
i'm working on - not just the reporting one for the contest... I'm
modifying it so that you will also know the actual amount of time it
takes to do a rendering.

After a little tinkering, I've already found out that rendering as a
PNG file takes the least amount of time, but not by a huge margin...
more on this as I get more data.
 
Yeah I use that little trick of setting the background to "None" when
rendering transparencies. I save to tiff and in Photoshop I can change
the background color for different dramatic effect.
 
I'd love to see the macro once you get it done.

"- not just the reporting one for the contest" What is this macro you're
working on??
 
TOP said:
I know there are a lot of people who render parts or relatively small
assemblies. What about multi-thousand part assemblies? Exploded views
of assemblies with a few hundred parts?
Click to expand...

We were hired to do some very large (8000x8000 pixels... for trade show
banners) of very large (10,000 part) assemblies. That was the job that
started the 3GB switch discussion a couple fo years back, which you
might remember on the newsgroup.

Yes, it can be done, even with shadows and indirect illumination. The
big obstacle we had was running out of memory.
1. Create a simplified config and hide anything that won't be visible.
2. Watch your depth settings. When raytracing mirrored parts you can
get by with 3-4 levels and it will look OK. For refractive, you need
enough for the light to get through translucent materials (example - on
a hollow box, you need four - one for each surface)
3. Of course you can experiment with settings, but you will be
suprised (I was) at what you can get away with. Middling shadow
quality, midling indirect illumination, decent anti-aliasing, etc, were
all possible
4. Use the memory management. If you don't know how to set that,
please post back and I will look up what we used.
5. If all else fails, the magic trick that saved our tails on the job
was to cut down on the display quality in tools-options-document
settings. On the largest assembly we did, this was the only way to get
the rendering out.
6. If you do a lot of this, get an extra computer and run your
renderings on it. This way you can keep working on other stuff while
the extra computer chunks away at the rendering.
7. Keep a log of settings and rendering times. I always put the start
time of the rendering in the file name - the end time of the rendering
will be in the date/time of the file when it is finally complete. This
way you can optimise your settings to get the best quality with
reasonable/realsitic rendering times
-Ed
 
Thanks Ed.

The display quality setting will be tricky. We have to have it up to
keep lines from bleeding through thin walls. SW has trouble with 100ft
diameter 3/16 thick walls with detail on the backside. Maybe this won't
affect Photoworks.
 
I'm in the middle of a study (of my own) which will show how different
settings affect rendering times. I'm not finished yet, but I've
already learned some very revealing information:

1. I've not found a significant improvement on rendering times for my
computer at work (3.19Ghz, 2G ram Xeon sytem) versus my computer at
home (2.4Ghz, 1G Ram Opteron system, true 64-bit... slightly faster
rendering times). Hopefully there are some settings which will help
this. Overclocking is a possibility.
2. If you have lights in your model, the EDGE QUALITY setting has the
largest impact on rendering times (you wouldn't believe how much).
3. I don't see any reason to use anything more than the "Medium"
setting (default) for anti-aliasing. Using "High" or "Very High"
increaes rendering time dramatically, with very little perceptable
improvement in image quality.


More to come on this matter... stay tuned.
 
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