Author Topic: 3D Parametric Cross Sections (paper space suggestions)  (Read 6536 times)

Lar

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3D Parametric Cross Sections (paper space suggestions)
« on: May 12, 2012, 02:25:20 PM »
This is not so much a feature request but a heads up on issues the developers would have to address if they ever decide to implement the parametric cross section feature. Also, others can respond with their suggestions.

Note that this pertains to 3d cross sections and how they would work in paper space view frames, not parametric boolean operations. Here's the difference: A boolean would not change from view frame to view frame. A cross section could be on in one view and off in others.

To explain: A cross section involves normal entities in the drawing that would be all visible in most p-space views. However, in the view showing the cross section some of these entities would be visible, some partly visible and others invisible. Question is: how do we tell a particular p-space view that it must show the cross section only.

I don't know how or if this is addressed in TurboCAD but here's my proposed solution for dcad:

What shows in the cross section whould be defined by a 'cross-section entity' (let's shorten that to 'cse'). This entity would originally be created as a solid, then defined as a cross-section entity. Whatever is within the cse is shown but cut off if they cross the side of the cse. The cse could be irregularly shaped, not just a 3d box. The entities that get cut off should be 'healed', ie, their cut edges be closed up the way it works with a solid boolean operation.

The advantage of the cse, as opposed to a cutting line, is that you can define a small area of the drawing for 3d construction details. The color of the cse's could optionally be the color of the 'healed' faces of the entities that cross the cse. The user would be able to create hatches to place on the edges of the cut faces (to display the type of material). It may not be too far fetched to suggest that if a bitmap texture is applied to the cse then the cut faces will display the relevant portions of the bitmap.

The cse would have its own layer properties, like a paper space view frame, but you work it in model space. Maybe it should have an active/inactive toggle so you can edit it's shape or edit entities that cross its sides (while inactive). When active, whichever of the cse's layers are on (internally) will be be displayed and the cse itself would be invisible. The layers of the cse would automatically be switched off (externally) when the cse is active . The user can then add notes, dimensions or whatever else necessary on other layers that are not internal to the cse, so they can be displayed. This same principle would work in paper space where in a view frame the layer that the cse is on would be visible and the cse's internal layers off (automatically), but on within the cse. The other layers pertaining to the cse (the ones with notes and dimensions, etc) would have to manually be made visible for the view frame (by the user). A cse would automatically be activated in a paper space view frame if the layer it resides on is visible in the view frame. This way, more than one cross section or detail can be displayed in the same view frame. Also, you won't have to worry about activating the cse's before entering paper space.

To clarify: the cse could be activated in model space for viewing or printing.

The cse would cut solids as well as 2d entities, the same way it works for boolean operations (well, like 'section delete/cutoff' that work on many entities as opposed to just 2 solids). The points and edges of the cuts of entities that cross the cse would be able to be snapped to (when active). If a block or symbol crosses the cse sides maybe they should be internally exploded in order to be sliced. If so, the cse would need a refrest button and would be automatically refreshed when entering paper space.

The cse can be thought of as a dcad block entity with layer properties and performs a solid intersection on it's internal entities, so it shouldn't require a restructuring of dcad programming.

Lar
« Last Edit: May 12, 2012, 02:39:21 PM by Lar »

Rob S

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #1 on: May 12, 2012, 05:06:09 PM »
So tell me if i'm wrong, this would be a virtual contained surface slice of the model, thus displaying only what is inside the container, without actually damaging the model itself?

I would be able to edit my model, and go back to view "X" to see how it has affected that view?

I was originally only envisioning surface slice, with options to show what lies beyond that surface or not.

What you are describing seems much more useable, and not that much more difficult to develop.

A "cross section" or ":floor-plan" would them be created by a full-sized zero thicknes "CSE", is that the idea?

I think it would be important to have the ability to annotate such views in paper-space.
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MarkX

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #2 on: May 12, 2012, 05:59:30 PM »
You might look at how sketchup  does it. They allow you to place a plane anywhere across the model. Anything on the camera side becomes invisible, while anything on the other side is visible. The cut is virtual and the model stays intact.

Mark

Lar

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #3 on: May 12, 2012, 06:43:58 PM »
So tell me if i'm wrong, this would be a virtual contained surface slice of the model, thus displaying only what is inside the container, without actually damaging the model itself?
Yes. It would be as if you created a block from what is within the container with the 'retain' option, except what crosses the container's skin gets internally sliced. The original objects remain unaffected.

I would be able to edit my model, and go back to view "X" to see how it has affected that view?
You won't have to go to paper space to view the cross section. In model space you can edit the model with the container being inactive. If the layer the container resides on is visible you can edit the container as well (it is essentially a normal solid when inactive, except it has it's own layer dialog control) To see/print the cross section (in model space) you activate the container.

In paper space the container is activated automatically but the cross section is only seen in view frames that have the container's layer visible (the layer the container resides on in model space).

A "cross section" or ":floor-plan" would them be created by a full-sized zero thicknes "CSE", is that the idea?
Not sure what you mean by "full-sized zero thicknes" but the CSE (the container) is a solid. Only what is within the volume of this solid is displayed when the container is active, but only if it's layer is visible within the container.

You might look at how sketchup  does it. They allow you to place a plane anywhere across the model.
Actually, Mark, this is intentionally not the way Sketchup does it. As you say, sketchup uses a plane that cuts across everything so it can only do cross sections. This uses a volume with top(s), bottom(s), front(s), back(s) and sides, so the cut can be a bite out of the model, to isolate a beam detail, for example. Also, when I tried sketchup during its first release, the cut edges were not healed so you saw inside solids that crossed the cut line. I don't know if it's still that way (they asked for feedback then and I mentioned this and they politely responded with 'thank you, we'll look into it' and of course they did nothing about it when I checked the next release). Another thing is that sketchup produces a series of views that is good for a power-point type presentation (last time I checked). I don't know if it can produce a sheet the way paper space would.

You are right, though, in that the model remains intact.

Lar

MarkX

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #4 on: May 12, 2012, 07:59:23 PM »
Actually, Mark, this is intentionally not the way Sketchup does it. As you say, sketchup uses a plane that cuts across everything so it can only do cross sections. This uses a volume with top(s), bottom(s), front(s), back(s) and sides, so the cut can be a bite out of the model, to isolate a beam detail, for example. Also, when I tried sketchup during its first release, the cut edges were not healed so you saw inside solids that crossed the cut line. I don't know if it's still that way (they asked for feedback then and I mentioned this and they politely responded with 'thank you, we'll look into it' and of course they did nothing about it when I checked the next release). Another thing is that sketchup produces a series of views that is good for a power-point type presentation (last time I checked). I don't know if it can produce a sheet the way paper space would.
I take your point about being able to take a bite out of the model. That would be useful.

What SU does is more than a cross-section -- a cross section is what DC attempts to do currently though it seems to be bug-ridden.

SU needs LayOut (aka SU Pro) to do the equivalent of paperspace.

Mark

Dr PR

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #5 on: May 12, 2012, 10:04:45 PM »
Lar,

Your idea is interesting. I have thought about how to impelment cut away views, and I have always come up with the inverse of what you suggest. What is common between the drawing elements and the cross section solid would be invisible.

This idea came from looking at cutaway aircraft engines - the real thing. The pieces are machined to cut away parts of the case and other internal parts, usually leaving the rotating parts intact. Some of these things actually operate with moving pistons, crankshafts, or turbines. The edges of the machined parts are typically painted red.

Your idea will accomplish this same thing, but I am not sure I like it better - I haven't thought about it enough.

One problem with cutaways is that often you need more than one cutaway element. You may want to cut one piece at angle X and another at angle Y. Here is an example where I wanted to peel back layers in the warhead to different extents:

http://www.okieboat.com/Copyright%20images/Mk%2046%20CR%20warhead%201024%20C.jpg

I created the full 3D model first and then subtracted (Solid Subtract) a sequence of solids with increasing angles from each successive layer of the warhead. I used DesignCAD's unique feature of making the cut edges the color of the subtracted solid to make some edges red. I use this a lot for illustrations.

Here is another example:

http://www.okieboat.com/Copyright%20images/XSAM-N-6%20booster%20cutaway%204%201024%20C.jpg

You can see that the cutaway solid for the case was very different from the cutaway solid for the rocket grain (propellant).

The virtue of having the cutaway solid determine what is not visible is that the solid can be much less complex. Imagine creating the solid for the case or propellant grain that would show only what was enclosed - it would be much more complex than the relatively simple wedges that were used to subtract from the model.

Here is another example of a fairly complex cutaway:

http://www.okieboat.com/Copyright%20images/RIM-8%20burner%201024%20C.jpg

On the other hand, if you want to display only a thin slice through a drawing, like a horizontal cross section through walls of a building, your idea of showing only what is enclosed within the cutaway solid makes a lot of sense. So maybe the best solution is to have a switch to show what is enclosed within the cutaway solid, or show what is outside the solid. That's easy for me to say - DT and company have to figure out how to implement it.

However it is done, I agree that the sliced solids must have a visible edge, and we must be able to control the appearance. Solid colors like the Solid Subtract function produces are the minimum requirement. Hatches would really be nice!

Phil
« Last Edit: May 12, 2012, 10:11:14 PM by Dr PR »
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JJG

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #6 on: May 13, 2012, 12:07:13 AM »
Dr PR,

to do such results as on your links, why not use a "selected only" option in the feature asked by Lar ?
This way, it would be the classical way how Designcad works.
 ;)

Lar

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #7 on: May 13, 2012, 12:10:44 AM »
Phil,

I agree that some cases would be simpler for the solid to be subtracted and I like your idea about the switch. This would be equivalent to the 'section trim' command (D) that has the option to trim inside the box or trim outside the box.

All of these cuts were always possible in dcad. The only problem is you have to duplicate the model and cut that if you still needed the whole model. If changes were made to the model you had to repeat the process. To create a paper space sheet with the present method is no problem because you can simply put the cut on it's own layer. With the parametric method printing a single cross section alone, from model space, is no problem either but how do you do a paper space sheet where in one view you see the whole model, in another you see a half of the model cut away and in another you see nothing but an internal rectangular portion of the model. This is what my suggestions try to address.

Does anybody know if this concept is possible in TurboCAD, Solid Works or Revit and if so, how it is done in those programs? I've seen it done in Chief Architect where a view can be defines as a plan, an elevation or a regular flat cross section but I have never seen 3d cross sections or 3d details.

Having the cut edges take on the color of the cutting solid is not unique to dcad, though. Cinema 4D also does it at a whole other level in that what ever material properties the cutting solid has is given to the edges. So they can be transparent, bumpy, reflective, etc. You can even use a saved animation as a material and the animation will play across the cut edges.



Lar

prl

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #8 on: May 13, 2012, 12:24:19 AM »
Lar and Phil, interesting concept(s).  I believe Lar once posted a picture of a house that used the "subtractor" or "take a bite" out of the total model approach. Both approaches are in essences the same thing. One keeps everything within the "bite" solid, the other everything outside the "bite" solid.   Keeping in mind the "take a bite solid" can have any shape not just a cube or rectangular solid.  In theory DesignCAD has always been able to do this though it is destructive so everything is done with a duplicate total model.  In DesignCAD for the self-healing, everything needs to be a solid(s).

I've done variations of both within the limits of what DesignCAD can accurately subtract.  My approach is to take a "bite" snapshot where you decide if you keep the interior contents or the outside, copying the results to the clipboard and with undos a few times to return to the original. The clipboard contents are then pasted into the drawing somewhere off to the side.  To be safe, this is always done on a copy of the model too.  Of course, none of this is dynamic, it is a static "bite" shot.


Edit:  While I was typing looks like Lar posted too.  What are you doing up?

Lar, your approach is one for a complex set of viewing planes or rules, basically a "viewing" solid.  You want DC to make visible everything within or outside a complex shape that also has skinning features which is then viewed through a 2d viewport in paperspace.  The paperspace viewport would have various toggles for the "bite" viewing solid: show interior, hide interior, or off .

Once I take this Revit class, I'll let you know how this is tackled.  Presumably they have made it dynamic.  



I've attached a few quick example pictures using the subtractor solid "bite" method.

Pic s1 is the subtractor solid.  Pic s3 has all the individual barn members "define solid" to create a super solid, then a subtraction with the blue subtraction solid.

Pic 5 is the inverse.  There is a large "world" cube solid around everything and the blue subtractor solid is subtracted from the "world" solid.  Now the "world" will be subtracted from the barn super solid.

Simple huh!  (Your mileage will vary in each and every DesignCAD release.  This was done with the version 22.x beta).



 
« Last Edit: May 13, 2012, 05:09:19 AM by prl »

Rob S

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #9 on: May 13, 2012, 07:14:33 AM »


I think however it is achieved, the key point needs to be that the views can be all active at the same time, and nothing is ever actually subtracted or sliced from the model.

It should be possible to combine different sections and chunks displayed on one single paperspace view, in different viewports.

Mini-BIM coming right up!
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Dr PR

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #10 on: May 13, 2012, 11:10:10 AM »
JJG,

I agree that a "selected only" feature will be needed, whether it is for visible objects included within the cross section entity (inclusive CSE) as Lar described or visible objects outside as I described (exclusive CSE). I think we have shown examples for both approaches.

Also, simple cutting planes are not adequate for complex cutaways. Multiple cross section surfaces are required. Since we are talking about 3D drawings it is appropriate that CSEs are thought of as volumes of space that control visibility. Only objects inside or outside the volume will be displayed. Maybe they should be called "visibility control volumes" or something like that to distinguish them from ordinaty solids. They could be created in exactly the same way as current solids. In fact, maybe that is the way to create them, as ordinary solids, and then transform them into CSEs. This way any solid could become a CSE.

One thing to keep in mind is that some jobs may require many CSEs, as my cutaway warhead illustration shows. In some cases each object in a multi-part drawing will require its own CSE.

A given CSE may be used for several objects and another CSE for just a single object. For this we need to be able to select a CSE and then select the objects it is associated with. Conversely, we need to be able to select an object, highlight the associated CSE, and remove that (and only that) object from association with the CSE.

The appearance of the cutaway surface of solids is another matter. In some cases you may want it to look like just another surface of the solid, with the same material properties. In other cases you may want the surface to have a different appearance than the parent solid material. What happens if you want to use a single CSE with multiple solids, and want each solid cutaway surface to have an appearence different from the parent solid, and a different appearance for each individual solid? For example, imagine a bunch of layers in the cross section and each cross section with a different hatch pattern, all created with a single CSE.

You may want to use multiple CSEs on a single solid to generate two separate cutaways with different characteristics.

How do you deal with overlapping CSEs? What if you have two CSEs intersecting a single solid, and overlapping? If you assign the single solid to both CSEs and they do not agree as to what should be visible/invisible, what gets shown? What if you had one inclusive CSE and one exclusive CSE ovelapping in a single solid. One CSE would try to make the common volume visible and the other would try to make it invisible.

You can see that this could become quite complex.

Phil

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prl

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #11 on: May 13, 2012, 11:40:09 AM »
In fact, maybe that is the way to create them, as ordinary solids, and then transform them into CSEs. This way any solid could become a CSE.

Exactly.  You add together a bunch of solids to get the shape you want and then change it with the infobox from a normal solid to a viewing solid via check/toggle.  In model space, the viewing solid would show itself as a dashed outline. How it lives on layers and how it works through the 2d viewport would be an interesting discussion.  I haven't looked yet but in ACAD each viewport can have its own layer states (on/off) separate from model space.

John R

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #12 on: May 13, 2012, 01:31:41 PM »
…Does anybody know if this concept is possible in TurboCAD, Solid Works or Revit and if so, how it is done in those programs?
Lar

I think XClip in TurboCAD may be what you want.
John R.

JJG

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #13 on: May 13, 2012, 10:53:48 PM »
Thanks John R !

OK, when it's already exists in a IMSI-product, then why not transpose it in Designcad ?
unless it is a function related to the acis graphics engine ?

Lar

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Re: 3D Parametric Cross Sections (paper space suggestions)
« Reply #14 on: May 14, 2012, 06:40:44 AM »
…Does anybody know if this concept is possible in TurboCAD, Solid Works or Revit and if so, how it is done in those programs?
Lar

I think XClip in TurboCAD may be what you want.

John, I was referring to a paper space type layout that can show the entire model in one view and the cross sections in another. I'm also curious whether the cross sections can be in perspective and not just flat views (front, side, etc).

For you guys unfamiliar with paper space I've attached a dcad file example. The file will open in paper space looking like the attached jpg. Turn on 'automatic rendering' (in the view menu in paper space). Select a view frame (best to have point select mode on to be able to see which frame gets selected) then click the sun in the paper space toolbar to see which layers the view frame is displaying. You can examine the actual model and layers by exiting paper space (file menu>paper space mode). The sections and detail in the drawing were created by duplicating the complete model and performing a boolean operation on it, which results in a bigger file size and are not parametric.

JJG,

I agree that a "selected only" feature will be needed, ...

I don't think 'selected only' would be practical here. I'm proposing that the containers have layers associated with them rather than actual entities.  If entities are associated this would be similar to blocks and we might as well stick with what we have now because the file size will grow. To understand what I mean create a new file and populate it with a few entities.  Save the file, close it then reopen it (to get rid of any undo memory) then 'save as' with a new name. Now select everything and define as a block, but with the 'retain' option activated. The 'retain' option will cause the selected entities to remain non-blocks but a copy of the block will reside in memory. This internal copy will increase the memory of the file. Now select everything again and delete it all. The only thing the file should be left with is the block in memory. Save and close this file then compare your 2 files sizes. The first file with the entities and no block will only be slightly larger than the 2nd file with no entities and a block in memory. If the container has layers associated with it it will just display what ever's on the layers and not have to duplicate anything internally.

After examining the view frame layers of the attached file you should understand what I mean by associated layers.

Lar