[Plugin] SectionCutFace v2.0

TIG · 20 Nov 2007, 18:35

I took a look see and I have a couple of problems with the script.
The colours list stops at the bottom of the page ending with the "L" colours and there is no way to scroll down to choose anything else. If I wanted a "White" face colour I could type "W" in the face colour field but then I would have to settle for "Wheat" because that is the first "W" and I can't get at the rest. The Cut face colour actually allows for the "Default" colour but the cut edge colour does not.

Press W to drop to Wheat then use the down arrow key to get to White...

sorgesu · 20 Nov 2007, 18:35

ahh thanks, down arrow within window, not in drop down list. Go it.
Now about the faces??

TIG · 20 Nov 2007, 18:36

@sorgesu said:

but there is space all around the doorway. Why is there no face in that space?
I thought the script fills in a face everywhere

The script attempts to work out what is solid and what is void, so it doesn't (usually) fill in every available gap. To see this draw a rectangle and offset it and pushpull it into a 'wall', reface the top and pushpull to make a quick floor and a roof; then draw a rectangle onto a wall face and pushpull it through the wall to make an opening. Now make a section cut across the wall passing through the window 'hole'. Use SectionCutFace on it and you'll get a filled-in section as you expect. But if you put a face or faces into the window as a 'pane' it can get confused as to which is solid and which is void in the cut. Usually if fills them all and you can then edit the section face group and select and delete unwanted faces, or redraw edges to (re)face something that's missed... Overlapping solids can confuse it as there's no simple rules to work out what's desired to be solid - typically the outer areas get filled, then any inner islands are emptied, then any nested islands filled etc (like CAD hatching ?)...

It's not foolproof...you should be able to make quick manual fixes to complex sections that get confused.

sorgesu · 20 Nov 2007, 18:37

I see. I have never really worked with AutoCAD but I'm teaching people who do and I didn't really understand what it is that they needed to have a face. I thought that they wanted a face even on a cavernous interior section cut. So I couldn't figure out why there was no face at all in an interior. Now I understand. Thank you.

stuartb · 20 Nov 2007, 18:37

I cant live without the sectioncutface ruby! Another thing I do now and then is to make the section faces 'not receive shadows'. This means you can cut further up and (when in plano view mode) still get the impression the cut face is moving with you. As the great man says . . . just ideas.

digby dart · 20 Nov 2007, 18:39

Many thanks for another excellent script TIG.

[digby dart]

chango70 · 16 Jul 2008, 12:11

That is just about one of the most useful rubys I've come across! thanks alot!

brokenstaral · 4 Sept 2008, 10:43

i m a newby at the ruby thing

is there anyway to render a section-cut after creating the section-cut face???

pilou · 4 Sept 2008, 12:04

Seems erase manually that don't you want (it's not a big deal) make the trick

brokenstaral · 4 Sept 2008, 21:19

@unknownuser said:

Seems erase manually that don't you want (it's not a big deal) make the trick

thanks man

that render is exactly what i wanted to do

i have also asked around a bit
other people say i need to use the intersect tool
so in that sectioned motor bike
did u intersect the section-cut layer with the model then delete what u dont needed??

or u used sum other method??

TIG · 8 Sept 2008, 18:22

It makes a group containing a large plane [face], intersects it with the model and then tries to work out what's solid and what's void. It doesn't always get it right...

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Gaieus · 9 Sept 2008, 13:20

TIG, I guess front faces and back faces are also considered during the "guessing phase" in your script, don't they? (Love the script BTW )

TIG · 9 Sept 2008, 19:41

@gaieus said:

TIG, I guess front faces and back faces are also considered during the "guessing phase" in your script, don't they? (Love the script BTW )

It should make the initial face looking in the right direction to start with... after that it deletes parts, so the remainder should 'always' face the expected way ?

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Gaieus · 10 Sept 2008, 09:00

I guess you are not asking this (with the question mark at the end).

OK, I see (and understand) that the face created tries to orient itself to "close" the section cut with the back face inside (or at least that's what I understand from what you wrote).

I actually meant that if in the model, the faces are oriented consistently, it helps the script with "guessing" what to keep and what to delete.

TIG · 10 Sept 2008, 14:45

@gaieus said:

I guess you are not asking this (with the question mark at the end).

OK, I see (and understand) that the face created tries to orient itself to "close" the section cut with the back face inside (or at least that's what I understand from what you wrote).

I actually meant that if in the model, the faces are oriented consistently, it helps the script with "guessing" what to keep and what to delete.

The orientation does not rely on the models's faces - it uses the plane direction of the section cut entity.
What is to be kept and what is to be erased is based on a faces' 'loop' look-up alogorithm. Working from the outside-most faces inwards (the outermost faces will not have adjacent faces on their outer edges so we know who they are), these are deleted and the next innermost faces are kept as they're the start of the cut faces. Then the next neighbour face is erased and its inner face neighbours kept and so on until it's all done. Obviously it's quite possible to devise certain shapes that produce collections of potential section-cut faces that aren't correct - if so, you can manullay erase or remake such faces to suit...

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plot-paris · 11 Sept 2008, 10:47

very interesting facts are discussed here. your method of approaching the faces from the outside bountaries is quite clever, TIG.

however, I see the great potential behind Csaba's idea as well. most of us, I asume, are modelling with a tidy face orientation. and it is likely to encounter huge and complicated models among our designs - models, where the current method has difficulties finding the right faces.

I think, the "start from the outline" approach has one big flaw: if it is wrong at one point, it bases all future decisions on this assumption, right? so when it does a wrong calculation, the only thing to put it on the right track again is another wrong calculation.

I believe with the "face orientation" approach this danger is not as great, because decisions are made individually, based on every closed shape seperately.
this method however can't just rely on the created intersection geometry, but has to refer to existing objects in the model as well. I guess this is quite a tricky piece of code to write.

it would be great (and I am dreaming here of course) to have both approaches and to test them against each other - to test their percentage of right calculations...

Gaieus · 11 Sept 2008, 10:57

It actually works pretty well - only faulting sometimes with deeply nested geometry.
What could be even better (well, say this is just dreaming because I understand it cannot be done unless with lots of individual faces) to animate this section cut like the "native" (but hollow) one in SU.

TIG · 11 Sept 2008, 17:53

@gaieus said:

It actually works pretty well - only faulting sometimes with deeply nested geometry.
What could be even better (well, say this is just dreaming because I understand it cannot be done unless with lots of individual faces) to animate this section cut like the "native" (but hollow) one in SU.

Section-plane methods are notoriously scant. However, it is theoretically possible to link the cut-face's group and its related section-plane using stuff like paired attributes and observers that watch what's changing. That way when the section-plane's location changes the matching cut-face group would be informed and it'd automatically "re-invent" itself based on this related section-plane's new location, direction, what it cuts etc...

Unfortunately I've tried this and I get Bugsplats aplenty ! I haven't found a work-rond so far... Perhaps SUp7 will have better methods for section-planes...

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roadkill · 11 Sept 2008, 19:46

thank you... so far i have been doing this in a complex and time consuming manner...

Gaieus · 12 Sept 2008, 07:28

When I use the script, I generally paint ever face within the group with the same material it cuts. So an animated script wouldn't add too much to my workflow if these faces couldn't retain the new material I gave them

Anyway, some different (enhanced?) method for section planes/cuts could be interesting if they were able to be exported (say in rendering engines and such). AFAIK it is not possible now.