topic How best to find the intersection points of two GDL objects in Modeling

How best to find the intersection points of two GDL objects

Anonymous — Tue, 23 May 2023 14:50:08 GMT

The image uploaded represents 2 framing members, modeled using Objective, viewed in 2D plan-view.

If I want to split/trim the ends off each one, so they bi-sect neatly with each other, how can I get the cursor to snap to the exact intersection of the outside lines of each object? (Without tracing the object with temporary lines, from corner hotspot to corner hotspot)

This apparent inability (AFAIK) to get guidelines and cursor snaps with GDL objects is a serious disability. Is it an AC shortfall, or some switch that add-on/GDL programmers need to turn on when they create their objects?

I wonder, because it's kind of inconsistent - a CadImage's Profiler object has one side of its object's profile, in 2D, as a "hot line" (where the cursor changes to a mercedes and intersections can be found). Unfortuately, the line on the other side of the profile (for a rectangular profile, for example) is completely dead, so it's not a useable alternative for me.

I'd use Objective for a significant amount of modeling if the guidelines and snapping were available. As it is now, I only use it when I absolutely can't use any of the inbuilt tools that do have these modeling aids.

Re: How best to find the intersection points of two GDL obje

Ralph Wessel — Sun, 25 Apr 2010 09:22:07 GMT

peter_h wrote:
Is it an AC shortfall, or some switch that add-on/GDL programmers need to turn on when they create their objects?

It is possible to create snappable edges on a GDL object. The trick is deciding where to put them. It's quite simple for the simplest shapes, e.g. rectilinear blocks, but the number of edges in a 3D body becomes enormous when curves are introduced, and particularly if the shapes is cut/rotated/bent.

If every edge is snappable, the object could easily become a nuisance. We're working on an algorithm to calculate useful edge snaps, but this is a challenging problem when you are given so much freedom in 3D. Note that this problem doesn't occur in section/elevation views because the object appears as a group of (snappable) lines in those windows.

Re: How best to find the intersection points of two GDL obje

Anonymous — Sun, 25 Apr 2010 23:25:18 GMT

Ralph wrote:
the object could easily become a nuisance

Ralph: Just out of interest...do you mean that it could bog down the CPU, or be a problem with isolating the point you want to select when surrounded by too many snap-points? I assume you mean the latter, as the CPU has no problem with all lines being "hot" in section/elevation.

Thanks for pointing out that it's different - and works as I'd expect - in section/elevation. Not just Objective, but all GDL objects, as I've just discovered! I hadn't realised this before now . But it begs the question... Why on earth is this super-productive ability crippled in plan-view - the most oft-used and useful view of all?

As for my 2cents with your future Objective improvements, relating to this issue...

How about a dropdown option in the Settings dialog:

a) No hot-lines
b) Hot-lines on long edges only {profile edges, not cuts}
c) Hot-lines on all edges {profile edges and cuts}

If this was user-selectable on a per-object basis, then we could customise the level of snapping, depending on the complexity of the object we are creating. So the decision as to what to make "hot" doesn't necessarily have to be automatic (and maybe not require as much coding of a sophisticated algorithm?).

This solution would suit me perfectly. If I had this option, I'd use Objective for ALL my framing and structural members, bar wall framing (which I'd like to be handled by the Cadimage addon, but I haven't gotten around to using it yet). So most of my uses of Objective would be timber rectilinear framing. So I'd mostly use option b, I'd imagine. Currently I'm barely using Objective for any of my framing , prefering, for horizontal framing anyway, to use plain wall elements (square cut ends only) or polygonal wall elements (for angle cut ends) - all because of the drafting aids that are available in plan view with these elements.

Re: How best to find the intersection points of two GDL obje

Ralph Wessel — Mon, 26 Apr 2010 13:33:00 GMT

peter_h wrote:
Just out of interest...do you mean that it could bog down the CPU, or be a problem with isolating the point you want to select when surrounded by too many snap-points?

Primarily the latter. A dense cloud of snap points can be a real pain to work around, especially when dimensioning. The former is also potentially an issue, but at the point where the object view is generated (refer to the next comment).

peter_h wrote:
Why on earth is this super-productive ability crippled in plan-view - the most oft-used and useful view of all?

Section views can take quite a while to generate (depending on size) because ArchiCAD has to generate a 3D body and then produce a hidden line view from it. If it did the same in plan, there could be a significant performance penalty. I believe this is why SEOs are not shown correctly in the plan view.

peter_h wrote:
As for my 2cents with your future Objective improvements, relating to this issue...

Thanks! Your feedback is much appreciated.

Re: How best to find the intersection points of two GDL obje

Anonymous — Mon, 26 Apr 2010 13:49:20 GMT

Section views can take quite a while to generate (depending on size) because ArchiCAD has to generate a 3D body and then produce a hidden line view from it. If it did the same in plan, there could be a significant performance penalty. I believe this is why SEOs are not shown correctly in the plan view.

hmm...so im curious...how GS team can make SEO working in plan ? Do you Ralph have any idea cos you are familiar with these limitations of archicad and programing...i m wondering cos this is very needed option in archicad ?

Re: How best to find the intersection points of two GDL obje

Ralph Wessel — Mon, 26 Apr 2010 14:10:48 GMT

NeckoFromSarajevo wrote:
how GS team can make SEO working in plan ?

I'm sure they've already done it for testing purposes and decided the performance penalty was too great. SEOs in ArchiCAD are not like the static boolean operations provided by many other 3D modellers. In those instances, the geometry created by the operation is persistent, so the overhead in displaying it in any view is quite light. ArchiCAD dynamically generates the geometry on demand, which can be very slow for some SEOs. We generally accept the delay in building a section/elevation or 3D view, but I'm not sure anyone would be pleased if the plan view took the same hit.

Re: How best to find the intersection points of two GDL obje

Anonymous — Mon, 26 Apr 2010 22:04:40 GMT

I run into this situation regularly.

Usually, I'm working in architectural designs, and restrain my slopes and angles to those a framing contractor can measure in the field (i.e. with sloped beams meeting up with skewed rafters.

If you view a drawing in plan view, and elevation view perpendicular to each member in question, you should be able to zero in on the point in question in all (3) dimensions. That's the technology I leverage via ArchCAD.

In the AutoCAD days when I worked in other offices, I had to copy-paste the (4) elevation drawings into a plan worksheet and position them just so – so I could draw rays connecting specific points. I tore my hair out.

Now, I can toggle between differen 3D views.

Not sure if it helped for what you're doing. Let me know if you have questions.

B.S.

Re: How best to find the intersection points of two GDL obje

Anonymous — Tue, 27 Apr 2010 01:52:42 GMT

bswain1 wrote:
"If you view a drawing in plan view, and elevation view perpendicular to each member in question, you should be able to zero in on the point in question in all (3) dimensions. That's the technology I leverage via ArchCAD."
Very interesting bswain1.
However, I'm not getting the concept in my head.
Any chance you could post simple example of what what your doing?

Thanks
lec

Re: How best to find the intersection points of two GDL obje

Barry Kelly — Tue, 27 Apr 2010 03:42:53 GMT

I know what you mean and it would be nice if any object's lines represented in a plan view at least would automatically be snappable to edges and intersections, etc. without having to script them into the object.
But as Ralph said this could become messy and annoying.

peter_h wrote:
(Without tracing the object with temporary lines, from corner hotspot to corner hotspot)

Have you tried using guide lines instead of actual lines.
They will automatically disappear when done (which can be good or bad depending if you need them again).
Very easy to place especially with the guide segment button.

Barry.

Re: How best to find the intersection points of two GDL obje

Anonymous — Tue, 27 Apr 2010 13:40:39 GMT

By toggling between two trace references of the two elevations, e.g. South and West, using a diagonal to locate points between the two, you can locate any point in x,y and z coordinates.

See attached image showing the West elevation trace references placed. They are placed so the reference elevations (e.g. ground level) intersect at the 45º diagonal as shown. The South elevation (turned off at the moment) is placed to the South.

You can see my guidelines representing the ground level and the point in question at the peak.

Usually, the 3D nature of BIM handles such issues without this procedure, except for little details like the one you're working with.

B.S.

Re: How best to find the intersection points of two GDL obje

Anonymous — Tue, 27 Apr 2010 14:38:09 GMT

Thank you for putting up the image bswain1.
Sorry to be such a pest, but the image you posted is too small to read or understand.
Any chance of re posting image a bit larger?
Even when I click on it, the preview is smaller not larger.
Could this be limit on size by GS?
lec