exploded view

December 23, 2024

AxoTools’ improved inverted extrude modes

Sometimes we need to extrude a shape as negative space, that is, space cut out of some other material. This was recently added to AxoTools, but with the latest free update, it’s now improved with three modes or variations on how to do this.

Extrude modes Recessed appears as a depression in a surface, similar to the “debossed” effect in Photoshop. AxoTools draws side walls and a back plane.

Cutout appears to cut the shape out of some thin material and move it backward.

Open appears as a hole in some material by drawing side walls, but leaving the back open.

All three modes add a mask to fit the size and shape of the opening.

If the inverted art needs to simulate an opening in a colored shape, you can check the option to “Add white background behind art.” This adds a white fill to the mask; otherwise, any colored art behind the extruded art will show through in Cutout or Open modes.

See the AxoTools online documentation for more information.

You can download AxoTools plugin for Adobe Illustrator, with 1,000 trial uses before purchasing.

November 9, 2022

Multiple line weights in technical illustration

Rick Johnson

You may have seen a recent video summarizing methods to use multiple line weights in your illustrations.

It’s probably helpful to go into a bit more detail and show more examples.

Using a single line weight (or “stroke width” as it applies to Illustrator’s path art property) is a simple and efficient way to work.

upper-left shaded line weight

By using more than one line weight, however, your illustrations can have more interest and suggest form.

One method assumes a light source in the upper left. Here edges facing away from the light are given a heavier weight. This was the standard where I worked at Kalmbach Publishing Co. in the 1970s. My mentors there told me it was adopted from a standard for US Patent Office drawings. It was easy to apply using pen and ink, but when they switched from Rapidograph pen to Adobe Illustrator in the 1990s, they switched to a single line weight. Adobe Illustrator, unfortunately, doesn’t lend itself well to multiple line weights, especially if the path is filled.

GP30 hood line example Here’s an example of an illustration I did using the “Kalmbach” method, drawn in ink at 1.5 times reproduction size. Detail lines were drawn with a 4×0 Rapidograph pen, and the heavy lines were probably a no. 0 or 1 pen. In those days, we typically cut an Amberlith overlay to add a flat tint to the background, which helped separate the subject from the background.

dual line weight A more common method called “line contrast shading” used in exploded-view parts drawings uses heavier lines on all outside edges of objects. In this example, the bottom of the cube and cylinder are thin lines because they represent the joint between two surfaces. A heavy line would suggest the objects float above the other art. In the case of the round hole, a varied line width makes a smooth transition between the front- and rear-facing edges. Complex illustrations can use three or four line weights. Standards are more like guidelines, actually, that vary between people and between businesses, often based largely on the personal preference of someone with experience and/or influence.

filter drawing

Greg Maxson drew these filter illustrations with pen-and-ink on Mylar for Hyster Co. back in the late 80’s. He explained, “You could really get lost in the detail with pen-and-ink. Lines within an object are thin, exterior object lines are heavier, and exterior object lines that are down and away from the light source are heavier and darker still. The heavying up of the lines down and away from the light source was typically used when illustrating larger equipment, machinery, etc. to give those objects more visual weight. Appropriate for rendering a bulldozer, but less appropriate for rendering the exploded illustration of an ink pen, for example. Of course, super thin interior object lines were/are common when used to represent less than 90 degree radii, and thin broken lines to represent a highlight along an edge, knurling, screening, etc.”

suspension drawing Greg used a three weight treatment on this Raptor suspension illustrations for Car and Driver magazine.

One more piece by Greg Maxson shows his skill at technical illustration using a variety of software, often including SketchUp, Illustrator, and others. Here he adds clarity to the subject with varied line weights, line colors, sometimes sketchy line treatments, and meaningful shading and textures in filled areas.

When AxoTools adds add multiple line weights, it places stroked paths above non-stroked filled paths so weights can change as needed anywhere along the object without affecting the fill. With a simple click of the Axo Line tool, you can toggle weights between thick and thin as necessary. In the coming months, users can expect to see more refinements in AxoTools handling of stroke properties. Please contact me if you have ideas that can make your work faster or easier.

November 7, 2020

Using oblique projections with AxoTools

Rick Johnson

Update: now with AxoTools 16.2, there’s an easier way!

Ron Kempke, who wrote the math behind AxoTools, has provided a follow-up to this post on using an auxiliary view in AxoTools, with these steps on taking it a step farther. Even with the oblique plane rotated at all three axes, we can still construct an auxiliary view and establish an axis for extruded art on that plane.

In this example, we have a simple cube with one corner removed. With the three sides projected, the triangle shape practically draws itself, but a problem arises when other objects need to be added that match this orientation.

Here, Ron walks us through this process using the AxoTools Projection panel along with Illustrator’s built-in Scale and Rotate tools.

To start, we need to do some construction drawing in the orthographic top view. You’ll probably want to work on copies of these views. Select the long side (hypotenuse) of the triangular shape in the top view. Copy and paste it, then rotate it 90°. Position this line to divide the shaded triangle at its right-angle corner at the corner of the cube. Use this as a guide to draw the red guide triangle.

Align the right angle of this triangle with the upper left corner of the right side view. Rotate the top view to match the guide triangle, as shown in the blue square below, then project this to the axonometric top view.

Use Illustrator’s Measure tool to measure the angles of this projected shape. Enter these values into the Axis fields of the Projection panel, which will then become a new (but temporary) axonometric view. The top face of the preview proxy cube in the Projection panel should resemble the rotated cube in your art. Note that these values are for this example only; your angles will certainly be different. If you now project the left and right ortho views, it should resemble the blue cube shown above.

Select the right orthographic view and scale it so that the shaded triangle matches the width of the red guide triangle.

Now on this foreshortened right side view, rotate a copy of the angled line -90° as shown. Here it’s colored green to distinguish it from red guide lines. Remember that having entered new values into the Projection panel axis fields, your projection now matches the blue cube shown below. Project the new guides into your axo view.

Measure the angle of the green guide line that represents the perpendicular, and save that value for later. Rotate the oblique surface and red guide lines so that the perpendicular is perfectly vertical.

If you’ve entered the new X and Z axis angles correctly, the top surface of the preview cube will be oriented at the same angles as your red guide lines.

You now have an orthographic (top-left) view of your oblique surface! Add your additional details. It’s worth noting that the red guide line at the top corresponds to the upper edge of the surface on the top view.

Now extrude any objects on this surface, along the vertical axis. You can do so visually with the Extrude tool, or numerically with the Extrude panel (be sure to check the Foreshorten option). If you have a left or right view showing the depth of the objects on this view and you’ve placed reference points for these views, you can drag by reference in the side view and the depth will be measured and foreshortened for you. (If you extrude a shape on this surface numerically from the Extrude panel, you should be aware that normally objects at this angle recede, so you’ll have to rotate it 180°.)

If you’re using reference points here, remember to redefine them in your standard ortho views when you’re finished with these details.

Finally, set your projection back to isometric or whatever projection your overall illustration used.

In review, the basic steps are:

Find the plane’s perpendicular from the top view.
Define a projection along the top perpendicular to find the plane’s side perpendicular, which is also its extrusion axis, from a side view.
Spin the oblique surface so that its extrusion axis becomes vertical.
Define another projection based on the rotated guides and un-project the oblique surface.
You now have an ortho view of your oblique surface that you can add details to, and save for future reference.
Project a top-left axo view and extrude any objects on that surface.
Spin the oblique surface back to its original orientation.

Many thanks to Ron Kempke for this useful and fascinating exercise!