Section planes cut improperly
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(A faintly similar problem was reported jan 08 in the general forum)
I see some odd effects when using section cuts in my house model.
a) as the section plane is moved some components get cut and other instances of the component get cut in the same place incorrectly - ie my rafters well behind the section get trimmed as the rafters intersecting the section plane get cut.
b) some components get cut in the wrong place altogether visually BUT when I use the plugin to add cut faces they appear in the right place.... so the geometry used by the plugin must be ok. I guess.
c) some components simply don't get cut at all but do disappear if the section plane passes their bounding box.I can supply images or models if anyone needs them to debug this.
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Hi Tim,
I myself have seen weird things with section cuts/planes, too. Indeed some images but especially the model file (a simple example file where you can reproduce this) would be wonderful.
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OK, here's a cut down house model. The section cut has trimmed the garage trusses but the little white rhomboids on the 'cut - Kitchen section' layer are in the 'correct' place.
Example Section Cut.skp -
Hi Tim,
I didn't see anything very abnormal, except that there was some quite heavy display clipping, and the clipping effect seems to vary when I move the section plane around. I wonder how my antique display card affects what I see. Is it this that is disconcerting you too? Does it effect exported images also?
Anssi
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Here's a short movie of what I see; basically the garage roof uses two different component trusses and all instances of each component get cut the same instead of each one being cut appropriately.
Oh. Right. mov files are not allowed by the uploader. Sigh. Here's a still instead.
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Hi Tim
Do you by any chance have an ati video card. I experienced similar problems, cutting groups and components scaled to a non regular scale/flipped. I´ve been told that it´s ati/apple´s problem. Google has already reported this problem, and all that´s left to do is wait. I no longer use that computer (it was an aluminum iMac, and i remember a big batch of these particular machines had nasty issues with the vidcard overheating, displaying weird triangles, the place i worked at had about 20 of those). I did´t see that problem on my own machine, a white macbook with intel graphics.
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@caronte01 said:
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...
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@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. -
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
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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.
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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).
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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.
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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.
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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
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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.
- don't
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Tim, I'm just curious. If you switch the camera to Perspective do you get the same clipping?
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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.
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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!
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