[Plugin] SectionCutFace v2.0

sorgesu

Okay, I have 2 models with the Section Cut face in them that are not working correctly. They are both in this folder on Kelly's site:
http://www.sketchucation.com/forums/scf/sas/Ruby/SectionFaceProb

Gaieus

Susan,

I opened the file "treasury2" and the section cut was there as it was supposed to be. See attached image.

sorgesu

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

Gaieus

You're right - it should fill that face, too - unless it is intelligent enough to know that that's the inside room of the building and does not need to fill it with a face. I'll go into it, I think.

TIG

@sorgesu said:

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

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

TIG

@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

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

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

Many thanks for another excellent script TIG.

[digby dart]

chango70

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

brokenstaral

i m a newby at the ruby thing

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

pilou

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

brokenstaral

@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

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...

.

Gaieus

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

@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 ?

.

Gaieus

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

@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...

.

plot-paris

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...