We will be drawing this using the curve tool, which uses Bézier curves and straight lines to allow one to define shapes. Originally created to allow for the modeling of French automobiles, Bézier curves allow the drawing of arbitrary shapes with a great deal of control, and without having one change affect another portion of the shape.
Please see http://pomax.github.io/bezierinfo/ for more information.
Each Bézier is composed of 4 points, an on-curve, two off-curve, and an on-curve points. Each off-curve point is associated with an on-curve point — this is represented by a connecting line — and the points should ideally follow some basic rules, both for best rendering, and for simplified drawing and editing:
- on-curve points should appear at extrema — that is the top-most, bottom-most, left-most and right-most points — if drawing a circle, there would be four on-curve points, one each, top, bottom, left, and right
- on-curve points should appear at points of inflection — that is, where a path changes direction — if drawing an “S” curve, then an on-curve point should be place along the mid-point of the form
- off-curve points should follow the “rule of thirds” for maximum smoothness (if desired) and should be approximately one-third of the way towards the non-associated on-curve point — that is, a given curve should have:
- an on-curve point
- an off-curve point about a third of the way towards the other path in terms of general distance, but may appear arrayed in any direction
- a second off-curve point should be about two-thirds of the way towards the remaining point
- an on-curve point
Thus a circle, when approximated (there is a slight degree of error) as Bézier curves and its on and off-curve points would appear thusly:
We will begin each path with snap to grid turned on, so as to ensure that the path will snap closed, and will place by either clicking or clicking and dragging and releasing either on-curve points which define lines (or places where lines begin/end), the on-curve point, or the pair of off-curve points bracketing the just-placed on-curve point. Place as many points as will be needed to create a given shape, trying to follow the above rules — the grid will necessarily distort the curve placement — for this step, position is not as important as number of points and their type.
Zoom into the path which one wishes to draw, click on the Design tab, click on the freeform Curve tool (fourth from the left), and begin drawing. Click and release will place a point for a straight line (or portion thereof. To get a curve, click, drag and release. The click places the on-curve point, the drag determines that there will be an off-curve point, the release determines where it will be.
After placing all the points and on/off-curve points, you should have something like this:
Note that it may help to decrease the grid size, so as to make it easier to position nodes aligned to other nodes.
Click on the “Snap to Grid” button at the top left of the screen, clearing the surrounding rectangle and turning off that feature, then click to enable “Node edit mode” (the middle Edit Mode button), then drag nodes to their desired positions:
Then switch to the “Curve Edit Mode” (the right-most button):
and adjust off-curve points until everything matches up as desired.
There are three editing modes for curve path objects (from left to right):
- Normal Edit Mode — this allows moving the object as a whole
- Node Edit Mode — this allows repositioning a node
- Curve Edit Mode — this allows adjusting off-curve node positions, and clicking on and dragging out of an on-path node will instantiate two off-curve nodes
Note that curve editing has a number of limitations in the current build of Carbide Create which argue for doing all of this drawing in another tool:
- off-node curve placement is limited to equidistant points on opposite sides of an on-curve point — this requires that one add additional points if doing asymmetric elements
- any use of the boolean operations will convert a path into polylines of straight lines which approximate the curves and are essentially impossible to edit
- no facility for non-tangential off-curve nodes — both off-curve nodes on the opposite side of a node must be aligned through the associated on-curve point.
Ideally there would be ways to allow one to:
- move an on-curve point as it is being placed (Freehand allows one to press the Command key to do this)
- add or delete on-curve points
- adjust off-curve nodes so as to not be tangential (the typical key for this is alt/option)
- adjust off-curve nodes so as to not be equidistant to the opposing off-curve node on the other side of the associated on-curve node
- contract an off-curve node into and on-curve node so as to create a point
- a keyboard option allowing one to constrain off-curve nodes to be aligned either vertically, or horizontally or at 45 degrees from the associated on-curve node (the normal key for this is shift)
One would then repeat this operation for each other needed path.