Section planes cut improperly

tim · 30 Jul 2009, 05:15

Hi Tim

Do you by any chance have an ati video card.

I do indeed - my iMac has an ATI 4850. I suppose it could be an opengl bug of some sort...

Gaieus · 30 Jul 2009, 06:58

@tim said:

...Oh. Right. mov files are not allowed by the uploader. Sigh. Here's a still instead.

Hm. I've checked in the admin panel and they were allowed. Now I changed the extension group to "downloadable" instead of "QT Media", please, try again. I'd like to see the movie, too (especially if not clipping is involved).
Make sure the file is not too big for the upload. If so, you can email it to me at gaieusatsketchucation.com and I'll try to upload it.

caronte01 · 30 Jul 2009, 14:51

In that case, it´s certainly a video card issue. I had an aluminium imac, similar to yours (the one with that same problem). It also happens on exported images (exported images also use hw acceleration) A workaround is to use layout to export images.

Please try the attached model
section test.skp
S

tim · 30 Jul 2009, 16:51

OK, loading the .mov file seems to work now - thanks!
This shows the cut plane moving back and forth. Note how the roof trusses (split into two slightly different designs) are cut in the same place rather than each one cut individually as needed. Note also that the intersection rhomboids on the cut plane appear to be correct.

iShowU-Capture2.mov

Gaieus · 30 Jul 2009, 21:46

I'd say it's definitely clipping. Check if any of the description and/or the solutions suggested here apply/help.

Otherwise there must be something with your video driver (try the whole thing without hardware acceleration in your Preferences panel > OpenGL settings - that's in the SketchUp menu on the Mac I believe).

caronte01 · 31 Jul 2009, 00:43

Hi tim, just saw your movie, and it looks a lot like the bug I was describing before. Try exploding everything and then doing the section again. I bet it will go away.

tim · 1 Aug 2009, 05:37

Well if I make each garage roof truss unique then each one display correctly trimmed. I'm not sure I can see a logical way that that effect can be blamed on a video driver but since I'm not expert in openGL details I'll have to hold my tongue.

I'm sure somebody somewhere will soon fix it. Hopefully before my bug-ninjas get to the guilty party and force-feed him/her/them mega-Jolt ultra-caff cola until the spleen quivers itself into hyperspace.

caronte01 · 1 Aug 2009, 16:42

Hi Tim

Please try this:

Turn off hw acceleration in skp´s preferences.
Quit sketchup (you have to quit and relaunch sketchup so hw acc is turned off completely)
Open sketchup again and try to do the section again.

s

tim · 2 Aug 2009, 05:11

Yeah, you're right; with h/w accel. turned off it draws correctly. That suggests to me that someone got a bit over aggressive in 'optimising' some code and assumed that all instances of a component would be clipped identically since, after all, all instances are simply instances of the one component, right?

There are two important rules relating to optimising code

don't
2)( for experts only) don't yet.

Dave R · 2 Aug 2009, 11:30

Tim, I'm just curious. If you switch the camera to Perspective do you get the same clipping?

tim · 3 Aug 2009, 01:54

Yup. Perspective or parallel projection makes no difference on my machine.

It's another case where I'd love to have access to the code involved so I could try to find the bug and suggest a fix to the relevant developer.

tim · 28 Oct 2009, 18:36

Good news; I just realised that SU 7.1 fixed this problem. You get so used to seeing something that occasionally it takes a nudge to notice it has changed....

It makes for a nice improvement in my house plans, so thanks SketchUpGuys!