drawing arcs

 From:  Michael Gibson
3437.5 In reply to 3437.1 
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:

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