QUESTION: Rendering Large Assemblies in PhotoWorks

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.

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

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.

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??

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.