I was unable to find, by searching this forum, much about arcs, specifically as it relates to the following questions.

1. Is it possible to constrain arc drawing, to a particular 3d plane in the 3d view port?

2. Is it possible to rotate an arc, onces its drawn, about an axis?

3. How do I draw the RED arc when its not constrained by one of the Orthographic projections, as illustrated in the attached pic.?

p.s. the cube in this pic is basically a skeletal reference for positioning the existing arcs, similar to what you refer to in the Moi command reference, under the topic, Construction lines.

1 Seems you must use the "Helpers lines" so your arcs by 3 pts can be anywhere ;)

call arc and don't release but click & move the mouse for draw any "helpers line" (even between the 3 clicks)
so your 3 points can be anywhere in the 3D space!



2 yes :) Select arc / Transform / Rotate as you want normal or by axe

3 yes : same 1 :)

PS "Helpers line" can be used with any functions!

Thanks! Am I correct that "Helper lines", do not work with the Center Arc?

No you are wrong ;)
"Helpers line" can be use before the first click of a function, after the first click of the function and before a last click of a function!

So you can use it for place the center of the arc, and after for place the first point and also for the second point ;)

Just click and move without release then release
When you want draw your point just click and release ;)
Just make some trainning! It's the more powerful tools of Moi for put with infinite precision something!

Say you must have a center arc at the middle of middle of the 2 lines top from the 2 volumes ;)
Helps line can help you ;)

Hi tomot,

> 1. Is it possible to constrain arc drawing, to a particular
> 3d plane in the 3d view port?

Not in v1, but there are a couple of different ways in v2 - in v2 there is a new CPlane function that lets you relocate the main drawing plane to be relative to some existing surface, but also in v2 you can just directly draw on planes in the model, like this:



For some more information and demo videos, check out here:
http://kyticka.webzdarma.cz/3d/moi/doc/V2releasenotes.html

look for the section labeled "Drawing / snapping on to surfaces".


> 2. Is it possible to rotate an arc, onces its drawn, about an axis?

Yeah, one way is to use the Transform > Rotate command, which will do a 2D type rotate in any of the ortho views, use a particular view to do a particular axis direction.

Or you can use the Transform > Rotate > Rotate axis variant which lets you pick the rotation axis by picking 2 points to define the rotation axis, that one lets you rotate around any arbitrary axis.

Additionally in v2 there is a new rotate widget that you can click on to get a multi-axis rotation widget, like this:




> 3. How do I draw the RED arc when its not constrained by
> one of the Orthographic projections, as illustrated in the
> attached pic.?

In v2 you could do it by setting the construction plane to be perpendicular to those 2 lines.

The arc will take its orientation from either the construction plane used in the viewport it was drawn in, or by the orientation of the surface that the center point was clicked onto.

Here's an example where I set the CPlane, draw the arc you want, then reset the cplane back to world:




Or an alternate way to get what you want that would also work in v1 would be to draw an arc flat on the plane snapped on to that short line, which creates an arc of the correct proportions, like this:



Then select it and use Transform > Rotate > Rotate axis to rotate it by 90 degrees upwards. Pick the ends of the arc as the rotation axis.


But again much of what you are asking about is greatly improved in MoI v2. V2 has a lot more stuff in it that lets you create geometry that is directly oriented in 3D how you want it, in v1 you are more limited to drawing things aligned to the world x/y/z axes only and then transforming it.

In v2 you would probably especially like the ability to just draw directly on surfaces because that is similar to SketchUp, just that in MoI you draw separate curve objects and they don't automatically embed themselves as part of the surface.

- Michael

Hi tomot,

> Thanks! Am I correct that "Helper lines", do not work with
> the Center Arc?

They do work for locating the center point arc's position, but they don't affect the orientation of the arc.

For the arc from center point command, the orientation of the arc will be determined by the construction plane in the view that you picked the center point in (actually it is the first 2 points, you can do stuff like click the first point at an elevation in the Front view, and then switch to the Top view and pick the start point of the arc, which will orient it towards the Top view in that case), or if you snapped on to a surface (in v2) it will take the orientation from the surface.

- Michael

As you see Michael uses any helpers above ! :)
So some methods are possibe for your problems ;)

And you can mix the 2 methods! CPlane + helpers!

Micheal:

That's precisely why I highlighted the 2 lines in yellow in the attached pic. A triangle is the absolute basic container to describe a plane in 3d space.

I was expecting an "intuitive arc command" to recognize the 2 yellow sets of co-ordinate points, so the arc command would use that data to draw the arc in the correct plane. Any arc in 3d space needs some reference, otherwise its just guessing.

How does the Cplane deal with this attached pic?
Using my "intuitive arc command" analogy above, this is one way I could use to draw arc's
on planes of an inscribed tetrahedron?

So the bottom line is: I need v2?

This beta should be available for input from users, like me, that remember AutoCad v2.5 which came on
5 X 5 1/4 inch floppies, and the agony of trying to draw in 3d :)

thanks! Frenchy, your becoming my shadow! we have to stop meeting like this and elsewhere :)

there is no CPlane in V1
So helpers lines and rotate axis will be your rescuers :)

Hi tomot,

> I was expecting an "intuitive arc command" to recognize the
> 2 yellow sets of co-ordinate points, so the arc command would
> use that data to draw the arc in the correct plane.

The arc command is expecting to use a plane to orient itself, not just a couple of line segments.

In v2 you can either draw a plane snapped on to those line segments and draw on that plane, or set a cplane there and then draw the arc.


> How does the Cplane deal with this attached pic?

It's not quite clear to me what you've got there in the model - do you have some actual planar surfaces there making the tetrahedron? If so then in v2 you can just draw the arc on those planes without even setting the construction plane.

It would help if you could post the 3DM model file with your stuff in it instead of only a screenshot, that will then let you show you with your specific example rather than trying to figure it out and reconstruct it (and possibly misunderstanding exactly what you have).


> So the bottom line is: I need v2?

Well, yeah - if you want to use the new stuff that has been added for v2 then you need v2.

Once v2 is released then there will be a trial version out for it.


> This beta should be available for input from users, like me, that
> remember AutoCad v2.5 which came on
> 5 X 5 1/4 inch floppies, and the agony of trying to draw in 3d :)

Well, it is available to users like you! :) Just purchase v1 and use your v1 license key to get access to the v2 beta. The v2 beta is available to all v1 customers.

- Michael

Here's one approach in V2 beta without using CPlane.

Hey good job Dan. Managed to get the old Commodore 64 out and load up MoI on it??? :o

Thanks Burr, actually it's a screen cap of my Timex Sinclair running an XP emulator. :P
(really compressed gif to 16 colors for the bandwidth challenged), in this case content
was more important than appearance. ;)

In that case, very impressive!! :o

Commodore 64.....thanks for dating yourself :-)


mshideler



ps: I owned one after my Vic-20.

I started out with a Commodore 64 as well, I learned how to do assembly language programming on it, which came in handy later on!

I drifted away from computing for a while and then got into computer graphics with Amiga computers a while later.

- Michael

>then got into computer graphics with Amiga computers a while later.

Hah, that takes me back - the Juggler!

I started out with a Commodore PET at school in about 1980, drifted away from computers then from 1989 I had an Amiga (a 500 with, eventually, a whopping 20mb HDD!). They were great little machines for the time, pity CBM never really invested in the platform. I learned a lot about DOS and shell scripts (I think I had some kind of bsh clone installed) as well as ARexx and basic C... That was when I was money poor and time rich. Happy days. The concepts I learned back then are still standing me in good stead today.

Dan