Topic: Matrix3d and TransformBy help

[It's Alive!]

I couldn’t find how to get the normal from the face (through the API).

What’s interesting is that Bricscad seems to somehow store the orientation of the solid. I’m NOT sure whats going on yet but it sure is acting different than AutoCAD

[MickD]

I've only looked at the lib briefly but using an edge traverser, graba vector from each of the first 2 edges, do a cross product on them and you have the normal of the face.

Basically, the cross product of any 2 vectors gives you a vector perpendicular to the plane created by the 2 vec's. This may vary on the 'winding' of the face edges though, as I'm assuming the traverser follows the winding of the edges it should be giving you a normal pointing away from the face (to the outside of the solid).

Just had a quick peek at the doc's, you're right, no normal!? Even if you get the face's surface.
I noticed that there are point on face etc methods so it must be there somewhere, just not exposed.
I's easy enough to get though using 2 edges of the face you want.
hth

[mohnston]

Checking the properties of a "box" type solid3d there is a width, height and depth.
However when that box is modified in any way (union, subtract etc.) those values do not appear.

Another thing I noticed is that there is some solid3d dxf information that is proprietary.

3dsolid group codes
 
Group code Description
100            Subclass marker (AcDbModelerGeometry)
70              Modeler format version number (currently = 1)
1                Proprietary data (multiple lines < 255 characters each)
3                Additional lines of proprietary data (if previous group 1 string is greater than 255 characters) (optional)
100            Subclass marker (AcDb3dSolid)
350            Soft-owner ID/handle to history object

I wonder what's in the proprietary data.

[MickD]

note the history group codes, this is new to the 2007/8/9 modelers, you may be able to get to the root object (it would be the first node in the CSG tree) if it's available?? When you extrude an object you then have the arrow on the extension face that you can grip edit the solid with making it's length longer.

Just a side note, with my C# code, I get a eWasOpenForWrite error on new solids created when I try and modify them with code, turning off SOLIDHIST and using the BREP command fixes the problem which I'll have to fix (probably an upgrade open or similar).

[It's Alive!]

I've only looked at the lib briefly but using an edge traverser, graba vector from each of the first 2 edges, do a cross product on them and you have the normal of the face.

Basically, the cross product of any 2 vectors gives you a vector perpendicular to the plane created by the 2 vec's. This may vary on the 'winding' of the face edges though, as I'm assuming the traverser follows the winding of the edges it should be giving you a normal pointing away from the face (to the outside of the solid).

Just had a quick peek at the doc's, you're right, no normal!? Even if you get the face's surface.
I noticed that there are point on face etc methods so it must be there somewhere, just not exposed.
I's easy enough to get though using 2 edges of the face you want.
hth

What is the best face to use, the face with the largest area?

[Spike Wilbury]

I noticed that there are point on face etc methods

yep... there are some methods avail... but for example the containment ones, do not work...... at least for me...

I tried to move the extreme (2+) points I found aligned to the solid into a face and no luck, I will try to use the mpolygon combination.

With that I can find the face I need and calculate the direction....

A lot to play for this weekend....

[mohnston]

Thought this was relevant.

http://through-the-interface.typepad.com/through_the_interface/2008/09/traversing-a-3d.html

[Spike Wilbury]

Thought this was relevant.

http://through-the-interface.typepad.com/through_the_interface/2008/09/traversing-a-3d.html

Thanks, that's the easy part.....

[Spike Wilbury]

After more than 120 days.... here is something.-

Base on the work of Gill Barequet

Here.-
http://www.cs.technion.ac.il/~barequet/

I was able to use it inside of my ObjectARX project.

Attached it is the arx, and a drawing (a2007) - for testing.

Note:
This is a beta - debug and not full tested, so expect ERRORS.

How to use the command OBB:
Loaded in the attached drawing, call the command OBB, select a solid and the command will draw four points around the oriented bounding box, if nothing goes wrong

Looks, to me that have future, give it a try.


Luis.

[SEANT]

Definitely looks good on all the slab-sided solids in the drawing.

As a point of interest though; it causes a fatal crash (AutoCAD 2009) if a cylindrical object is selected.

[Spike Wilbury]

Definitely looks good on all the slab-sided solids in the drawing.

As a point of interest though; it causes a fatal crash (AutoCAD 2009) if a cylindrical object is selected.

Yes, because when it does the traversing on the faces, it returns two points and they are colinear, that's why

I will continue playing with this project, and as soon became more stable, will post it in the was C++ forum - the VS SLN.

LE!

[It's Alive!]

Nice work Luis.. 

[Spike Wilbury]

Appears that this new algorithm it is working - a total new approach.   

So in case someone wants to run some tests, please do it and let me know if works as expected.

For now, it will just draw two points that are the min and max at the oriented bounding box found and a line between both points.

Again, please remember that this is a debug version and might have or generate some errors.


Load the arx file and call the below command name:
Command: OBB


Note: I have not implemented the function to work with spheres, pyramids, cones.... I'm working on that, at this moment...
Thanks!

[MickD]

OBB doesn't work for me, sure it's the right command?
thanks

[Spike Wilbury]

OBB doesn't work for me, sure it's the right command?
thanks

Hi Mick,

Let me upload the file, one more time...