Creating cone or pyramide

Drafting questions
nananaj
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Joined: Sat Jan 24, 2015 11:19 am

Creating cone or pyramide

Postby nananaj » Sat Jan 24, 2015 11:26 am

I'm trying to build a simple 3d model with pyramide and do not find a ways to do that.


Seems that slab generator allows to create only the parallel surfaces, the same with face generator.

How you create objects that have inclination in several dimentions, not just one?

May be I missed some step in documentation, too :)

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MikeCauser
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Location: Cambridge, UK

Re: Creating cone or pyramide

Postby MikeCauser » Sun Jan 25, 2015 2:10 pm

Look in the 3D manual for "Ruled Surface". If you want the top of the pyramid to be a true point you would have to be very precise with the definition -- it will be easier to have a very small flat face on the top.

Mike

nananaj
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Joined: Sat Jan 24, 2015 11:19 am

Re: Creating cone or pyramide

Postby nananaj » Sun Jan 25, 2015 5:36 pm

Thank you a lot.

This seems to be working except that

"The resulting model is built by the two parallel profile faces with tiles joining these faces at whatever angle a straight line can be ruled between them."


So for a little bit complex figure - I cannot use this method. May be you have a hint how ti model this kind of figure in 3d (I'm not sure I drawn ZY view correctly:) ?
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MikeCauser
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Re: Creating cone or pyramide

Postby MikeCauser » Mon Jan 26, 2015 1:22 am

nananaj wrote:"The resulting model is built by the two parallel profile faces with tiles joining these faces at whatever angle a straight line can be ruled between them."


Riiiight. I am sure there is a quick way to do this, but cannot remember quite how to do it -- it is 25 years since I last used Medusa 3D in any serious way :?

May be you have a hint how ti model this kind of figure in 3d (I'm not sure I drawn ZY view correctly:) ?


OK, here is a way to make the model, not as a solid but as a shell, which is the way you need it to be to use sheet-metal unfolding for example.

xxx.jpg
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This uses the Face Polygon Generator, and I've changed the viewboxes because your doubt about ZY view was correct, you were looking from the wrong direction.

This object has a number of Profile Lines that lie on top of each other, so the Modeller will get very confused about which Link Line connects which Profile Lines, unless we add a bit more structure to the data. To show the structure -- and to help edit it -- I have added the Structure Tree window (click the garden fork at the bottom right of the main window). Each pair of Profiles and their Link are in one "Group" of type CPL. Note this is not the "group" used to temporarily bring things together in 2D. This is permanent, stored with the sheet, and is actually called "Clump" internally and in some parts of the documentation. One of the CPL clumps is selected so you can see the Profile and Link lines in red.

The documentation shows an alternative way to clarify the relationship of the Lines, by having a pair of view boxes for each face. This saves the messing around getting the clump structure right, but makes it much more difficult to make changes later.

Send me a message if you want a copy of the .she

I'll keep thinking about a better way to do this and make it a real solid.


Mike

nananaj
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Joined: Sat Jan 24, 2015 11:19 am

Re: Creating cone or pyramide

Postby nananaj » Mon Jan 26, 2015 6:27 am

Thanks you so much for such a detailed instruction.

I'm fine with having 'shell', as I will unfold it later, that was the whole purpose. I tried to follow steps in a documentation to create a tetrahedral, as they suggest, but without much success )

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MikeCauser
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Re: Creating cone or pyramide

Postby MikeCauser » Mon Jan 26, 2015 8:05 pm

I have created a valid solid model of this, but before showing how I would like to explain why this is not a click, click click function on the menus.

The "pyramid" is only symetrical about one axis, and in orthogonal view only one of the six faces is seen as a true view (the bottom). So at least one of the other five faces has to be created in a non-orthogonal way. This is actually an improvement over the previous method because all five tilted faces had to be separately defined.

This model is created using "Meshed Surfaces", which are sometimes called "Lobster pot" in the documentation. To create this I made two closed surfaces, the top and the bottom, called "LATITUDES", and four wires to join them, called "LONGITUDES". But first I need to create a true view of the top face.

36.jpg
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In the bottom right View Box is an "Oblique View Primary" with the label "A". in the top left View Box I have deleted the old Iso prim and added an "Oblique View". The direction of the second one doesn't look quite right because it is free to rotate around the axis, but I've set it so the view is correct in 3rd Angle. Then with one Sweep that is a square in plan and a cutter that is at the same angle as the oblique view I can now create the "true view" of the top surface. I have added dimensions to show that it is not quite square. This model view is now copied as a Profile Line for use at the next stage.

Nearly reached 2000 character limit, so look for next post.

Mike

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MikeCauser
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Re: Creating cone or pyramide

Postby MikeCauser » Mon Jan 26, 2015 8:15 pm

OK, on we go....

22.jpg
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The top Profile has a Line Generator line with point function 10 on one corner and a point function 12 to show the depth of that point in the ZX view. Point function 12 (as specified in manual) is Centre Line in the linepoint popup menu. Then a text TMG is placed on the line with "LAT P", meaning this is a Latitude of object P. The bottom Profile also has Line Generator line, but a depth arrow in ZX.

In the plan view (YX) each Longitude line is drawn, but in ZX just two Profiles are needed. The Line Generator lines need a point function 10 in YX and a function 12 in ZX. Now build the model.

This is all harder to describe than to do -- once the words used in the manual have been translated into what the menus display ;)


Now some bad news for Medusa Personal users. I can only find a really crummy interactive model viewer. The full control of perspective and light sources for shaded pictures is denied to us :geek:


Mike


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