Another blotchy rendering question...

[mcramblet]

I posted this in the rendering settings discussion group, but then I thought this might be a better discussion group for it:

I've been playing around with my sons education version of Keyshot 3. I use a different rendering application at work, but I like the simpler interface, the ease of use, and the speed that Keyshot can have in rendering. I'd be very tempted to push for a change to Keyshot, but there is one problem that keeps me from making the recommendation, and that is the blotchy shadow issues. I work for a packaging company and I frequently need to show clear plastic sealed or trapped between paperboard cards. This seems to be something that Keyshot struggles with. I'm aware of the fact that there needs to be a little bit of space between the plastic and the cards when a package is modeled, so I add a space, but still have issues. In the attached examples, I'm showing thermoformed cavities that are to be sealed to cards. In this model, I've placed a space of .01" between the cavities and the cards. If I render a close-up, it's not too bad, but a shot that shows the whole package looks really awful. I've done some looking on the forum and one piece of advice I see is to use the max. time rendering. I've tried that and I'm not happy with the results that gives or the time it takes. The simple interface and ease of use is a big plus, but the fast renderings is the most important. The speed of the rendering is the biggest selling point of a proposed ROI, if I were to request that my company makes a switch. If I need to set up every render to a max time of an hour or two to get good results, all the speed is lost and there isn't much of a point in making a switch. I'd really like to see if I can find a solution that cleans up this issue, while maintain a relatively fast rendering time.

[Chad Holton]

Have you tried KeyShot 4? If not, here's a link: http://www.keyshot.com/try/
Also, I played with a model I have that looks similar to your scene but can't seem to get the same result. Could you share a simple scene that is giving you this issue?

[mcramblet]

I have tried a demo version of Keyshot 4. I did another test this morning (with ver 4) using this same scene, with the same results. I'll attach the scene to this posting.

[Chad Holton]

Thanks for sharing the scene. Doesn't seem that this is a blotchy shadow issue but more about slow rendering times?  ... some materials just take longer to render and you just have to play around with the scene to see what you can getaway with. I'm checking it out now and noticed a few things that may help speed things up without having to add faster hardware.  You can probably getaway with less raybounces and even a less shadow quality. Not sure if you need ground shadows or reflections turned on either? If not, this will help with rendering times as well. As for the whole scene not looking good, you may want to play around with different environments to help make the clear plastic pop a little.

[mcramblet]

Even with the current settings of the file, the rendering time isn't too bad. It really is the blotchy/dirty look under and around the plastic (the 2nd image in the first posting). Some of the settings, like ray bounces and shadow settings are me playing around, trying to see what might help in cleaning up the issue.

[guest84672]

You would need to crank up GI quality. We will run some tests here.

[KeyShot]

There are two issues in the scene not related to global illumination. First the scene contains tiny lines in the plastic geometry. To samples those properly it would be good to increase the samples from 16 to 64. Secondly, 'sharp shadows' is turned off. It should be turned on to capture the small shadow features on the face - otherwise it will be blurry as you are observing. You can reduce the shadow quality as I don't think it has to be that high.

[mcramblet]

I tried using the suggested settings, but the issue is still there. Did the settings eliminate it for you? Can you post an image showing the results of your rendering?

[mcramblet]

Would it be possible for you to post a screen shot of the rendering settings and the rendering that you get from it? I'd like to see it and compare it to my results.

[mcramblet]

Here is another example from a different CAD model test. This model is similar, the thermoformed clear plastic would be sealed to the paperboard. I this one, too, I've added a small space between the plastic and the board. It looks like the package has a severe mold infestation.

[Chad Holton]

Here's what I ended up with after about 30-35 minutes on an eight core machine. I turned off ground shadows and reflection to speed it up a little. Could have baked a little longer but not getting any mold. If you want a resolution higher than what you can get with a screenshot, you'll want to use max-time and set it for a couple hours or so, depending on what all you turn on and your equipment.. but if it looks good in 30 minutes, you can stop it and save. That's the beauty of using max-time. 

[mcramblet]

Hmm. So it appears that I might be stuck using the max time rendering. I was really hoping that there might be some settings that would allow the use of the Advanced control rendering which was so nice and fast. This sort of kills the ROI that I was going to propose. Cranking out the renderings the in the 15 minute range was what I was getting while testing Keyshot using the advanced rendering, which totally blew the doors off what we are currently using. Planning on an hour or so using the max. time rendering is on par with what we are using. Bummer. 

[Chad Holton]

Depending on your machine and settings, you might be able to pull it off quicker... that's what I was getting at with my first post and helping you speed it up. Anytime you bump up a setting you bump up the time. Are these rendering for presentations, catalogs or what exactly?

[mcramblet]

They are renderings for customer presentations. We provide pre-production renderings of packaging concepts to customers so they can visualize what we are proposing. Quick turn around is often needed.

[DriesV]

Hmm. So it appears that I might be stuck using the max time rendering. I was really hoping that there might be some settings that would allow the use of the Advanced control rendering which was so nice and fast. This sort of kills the ROI that I was going to propose. Cranking out the renderings the in the 15 minute range was what I was getting while testing Keyshot using the advanced rendering, which totally blew the doors off what we are currently using. Planning on an hour or so using the max. time rendering is on par with what we are using. Bummer. 

I too find 'advanced rendering' mode unpredictable when there is global illumination behind transparant materials involved.  Too many GI artifacts even when GI quality is maxed out. I think I'm missing some setting or 'best practice' rule too.
Still, scene setup times should be lower than your old rendering solution, no? Do you have KS Pro? If so, why not let it run through the night using the rendering queue?

Dries