Faces/planes

soco · 12 Jan 2009, 11:13

Hey,
I'm trying to create a simple model from an imported Autocad floorplan. I have been trying to trace walls from the imported plan and extrude the resulting faces, but I find that often a face isn't generated by the lines I draw. To get around this I draw a rectangle and move its corners to resize the face to match the imported plan lines. Often, though, the corner won't 'snap' to points on the imported plan. Does this mean that the face I have created is not in the same plane as the imported plan? How can I ensure lines are drawn on a particular plane? Is my approach wrong altogether?

Sorry if this is a bit garbled - I haven't grasped the skp lingo yet!
Thanks,
Soco

I have had trouble extruding faces, particularly with one irregularly curved wall.

Gaieus · 12 Jan 2009, 11:30

Hi Soco and welcome.

It is often a problem with (ehm... "sloppy" CAD files) that they are either not coplanar or the lines do not form a closed loop so as to act like edges of faces in SU. Also, CAD imports come in as groups and you can only create faces by retracing certain edges in the same editing context they are so you will need to double click on the group to edit it.

You can make a quick check whether your file is coplanar by clicking on different endpoints with the Text tool which - by default - displays the xyz coordinates where the z coordinate should be 0 everywhere.

soco · 12 Jan 2009, 12:11

Thanks for the swift reply. Great tip re the text tool... very enlightening!
I also have trouble 'snapping' rectangle corners to endpoints of skp lines. Would this be because the rectangle face and the point to which I want to snap are not coplanar? (I suppose a face can only be manipulated in the plane on which it is originally drawn, otherwise the face would have to split).
I am struggling to place a pitched roof on skewed/curved walls: is there a quick way of trimming one face (eg.a wall) with another, intersecting face?(eg.roof)? at the moment I am extruding the wall from ground level to just below the roof and then trying to bring the wall to meet the plane of the roof, segment by segment - it is very laborious and it's not always possible to snap a point on the top edge of a wall to the roof face.

Gaieus · 12 Jan 2009, 12:24

Well, the rectangle tool - by default - will try to draw the rectangles on any of the 3 major planes defined by the axes. If you have problems with coplanarity, there is another trick that might help: go to Window > Styles > In model (the small house icon) > Edit tab > Edge settings and at the very bottom, turn display edges by axis.

This will colour all your linework that is on any of the major axis into red/green/blue and whatever is off-axis, will remain black.

BTW it's about time to post at least an image or the model itself.

soco · 12 Jan 2009, 12:34

Great, I'll try that too... Thanks.
Re posting of model (though I'm not sure you could call it that!) we have a pretty strict IT department here, as well as a raft of security regs, so I'll have to run it past a few(dozen) people before I can do that. I'm public sector, not secret service, in case you're getting worried!

Gaieus · 12 Jan 2009, 12:39

No worries - there are a lot of professionals here who (for whatever reason) may not share their work in public.

Yet some close-up images where the "overall design" cannot be seen may be of no harm. Sometimes unhiding hidden geometry (View menu) also helps understanding what's going on with curved surfaces.

soco · 13 Jan 2009, 14:39

The Axes highlighting tool helps too... I realise I'm not drawing what I mean to draw much of the time! I've got the go-ahead to post a model, can I attach it to a post? If so, what's the best format?

Gaieus · 13 Jan 2009, 14:47

I'd go for skp.
Under the text area you are posting, there's the attachment tab.

soco · 13 Jan 2009, 15:08

Thanks, I see it now, cunningly concealed:)
Here is my masterpiece/mess so far then...

SU_model_130109.skp

Gaieus · 13 Jan 2009, 15:25

Wow, this is a realmess (if you don't mind me saying that).

raw geometry scattered all over on different layers
non-planar geometry intersecting each other all over the place
groups with illogical (or at least un-understandably misaligned) axes
lots of Z fighting (showing faces on top of each other)
have you seen hidden geometry on? (View menu)

Did you inherit the whole layer system from the CAD drawing? (Do you really need them?)

To really tell the truth,I'd definitely start over. I am really sorry to tell this but I'm pretty sure that with a better approach,you could get it quite right much sooner than cleaning this model up.

soco · 13 Jan 2009, 15:50

Don't worry, that's exactly what I was expecting. I'm very methodical usually, believe it or not, but since it was a first attempt I thought I'd throw caution to the wind (and hopefully learn from my mistakes!) Probably not the best building to start on, what with the irregularities. I will start afresh tho. Thanks for you help!

PS Can I remove the attachment now that I've embarrassed myself?

Gaieus · 13 Jan 2009, 16:00

IMO the best would be to bring in the siteplan but

make sure to "flatten" it in cad before.
Then try to get rid of the layers (delete them moving everything onto the default layer).
Then explode everything down to raw geometry.
Then erase every unwanted bits (the arc symbols for door openings and such...)
and now with a relatively clean model, start over but make sure you have all the floor plan of the double walls and all that are supposed to be connected pare connected etc.)
and only psuh/pull it up when you are already done with this.
those fancy roofs should be the last things to model.

soco · 13 Jan 2009, 16:26

Okay, thanks for the pointers... onwards and upwards!

soco · 14 Jan 2009, 12:10

Good morning!
Having further cleaned up my CAD floorplan and started my model again things are going much better. Mostly I can generate faces by tracing one side of a shape in the imported, exploded floorplan, which is a revelation! However it happens quite frequently that I cannot generate a face and this seems to be because one or more of the points involved has a Z co-ordinate of approximately(indicated by squiggley line)0 instead of 0. Is this another messy CAD issue? I draw in 2D only in CAD so assumed all lines in a plan would have the same 'Z' co-ordinate (ie. none at all). Is there some way of establishing a groundplane in SU with a fixed Z co-ordinate and 'gluing' the imported floorplan to it?

Gaieus · 14 Jan 2009, 12:23

Hi and good morning (it's already afternoon here )

There are several ways to "flatten" a sloppy CAD import (although flattening it still in CAD seems to be the safest way prior to import).

Anywy, there is a $ 10 plugin "Flatten.rb " at Smustard which can do that. If you are planning to use many CAD imports, it's well worth (just think about the time you have alreadyinvested in this particular problem). There are also other scripts there that help with sloppy CAD files.

Then you can always draw a big face under the imported linework and using the Drape tool of the Sandbox, simply "project and intersect" your lines onto that - obviously co-planar - face.

A third, quick,manual method (onlyif you have few faulty endpoints) is to move the vertices to 0 Z height. Deselect everything and hover over the culprit endpoint with the move tool. When you get the "Endpoint" inference, click on it, press the Up or Down key (to lock the move on the Z axis) and move it down to zero by inferencing to a known, good point.

With this latter method, you can often quickly fix some minor problems of lines/vertices out of alignment in other cases, too.

soco · 14 Jan 2009, 13:04

I just used the Drape method (discovering Sandbow tools in the process)and it's worked perfectly.
Thanks a million!

Gaieus · 14 Jan 2009, 13:23

Great!
Please, come back when you get to the next phases.

soco · 14 Jan 2009, 14:10

Well just when you thought it was safe to come out, I'm back! It looks as if I spoke too soon...
About 30% of my groundplan endpoints ended up with a Z-coord of 0.05, while the rest are at 0.00. I have doublechecked my groundplane mesh, which has all corners at Z-coord 0, and re-Draped, but the renegade endpoints won't shift. I completely exploded the CAD groundplan before export. In order to Drape it on the groundplane mesh I had to make it into a SU group (as I can only select one entity to drape) - could this be the problem (ie. will elements within a group drape properly)?

Gaieus · 14 Jan 2009, 14:40

Yes, groups should drape properly. Try to move your plan a bit above the face you are draping on. The drape tool should "project" all the lines smoothly.

soco · 14 Jan 2009, 15:40

I did that and re-Draped... I lost a few lines but those that did reappear were all on the correct plane. Redrawing a few lines is a tiny price to pay for having nice clean plan to extrude from!
Thanks, again.