Lesson 4: Drawing in 3D

2D multi-view (orthographic) drawings are very useful and easy to produce once you've had some practice, but they only give you part of the picture. If you really want to understand an object, you need 3D. After all, this is how we see the world!

The type of 3D drawing you'll learn in this class is usually called Isometric. Think of this as a drawing where all the vertical lines of a cube remain vertical, but the horizontal lines of a cube are skewed, and horizontal lines are parallel to each other on opposite sides.

This is based on the cartesian coordinate system where all points can be measured in space in absolute terms. Any object, and I mean anyobject, can be drawn in relation to a cube used as a bounding box. You'll learn how to do that in this lesson.

We're not going to get into perspective in this class, but if you're interested in drawing more realistic representations, I would suggest learning this skill from the Design Sketchbook.

## Constructing a 3D View

As with multi-view 2D drawings, the best way draw what you want to see is by using construction lines. Building a kind of cage around the object you intend to draw will make it much easier to realistically represent things like rounded edges and corners, will serve as a tool to measure proportions and locations of features, and will help ensure that the different faces of objects are consistent with each other.

Continuing with our 9V battery example, start by drawing 3 parallel lines in pencil. As before, use your fingers or your pencil to place target tick marks to ensure that they're parallel.

Draw a third parallel line for the back edge of the object. This line should have the same spacing from the line on the right as the other one does from the line to the left.

Next, draw the two bottom face of the cube. The angle of these lines will determine your view. Angles that are more acute to the horizon will show less of the top of the object, emphasizing the sides. Angles that are more oblique to the horizon will show more of the top. This will change the point of view of the object.

The point of view can be whatever you want, but a useful way to think about it is to imagine what it would be like to view the object in real life. If an object is big, the sides will be more prevalent in your view. If an object is small, you're going to see more of the top.

Make another skewed rectangle for the top of the box. These lines should be parallel to the ones on the bottom, and their placement should be roughly based on the proportions of the battery.

## Circles in 3D

To draw the terminals on the top, we'll need construction lines. A center line is drawn on the top surface by using tick marks at the midpoints of the short sides of the box.

Two other crossing centerlines will control the location of the terminals.

A circle in a 3D view is an ellipse. If you think of the circle as something bounded by a square (remember, you can think of any kind of object as though it's bounded by a box), you can see that the ellipse gets its shape because the box is squashed along one of its diagonals.

Just remember these rules of thumb:

1. A circle will hit the construction lines at the same points in 3D as they will in 2D.
2. The curve along the obtuse corners of the box get longer and flatter.
3. The curve along the acute corners of the box shorter and deeper.

With a drawing this small, you can probably just make the ellipses in one stroke with a little practice, but to get very clean ellipses it helps to draw them in segments.

Remember the rules of thumb, and you'll get good results.

The positive terminal has a hexagonal profile. In this distorted view it's basically the same thing, just compressed vertically. There's no point in getting too technical with constructing this feature, a rough approximation will get the point across.

## 3D Form

When you look at the top view of the battery, you'll see it has rounded edges. To draw that in 3D, the sides will be offset from the boundary made by the construction lines. You'll see why in a moment.

The rounded corners have small radii. To draw the boundary edges of the rectangle, small gaps are left at the corners of all the intersections. Remember, it's best to draw arcs and straight lines separately to get the best results.

Small fillets finish off the corners for a realistic look.

The negative terminal is a cylinder, so all it needs is vertical lines to complete the shape.

The outlines of the positive terminal are next. It's important to pay attention to which lines will be seen in a particular view. The edge of the lower hexagon will only be visible on the front, for example.

With the line work mapped out in pencil, it's time to assign line weight with pens.

The line weight rules are the same with 3D views as they are with 2D. In the video I'm only using two line weights, but for a bigger, more precise drawing, this is how you would handle the line weights:

• Extra Light: surface details
• Light: corner edges
• Medium: edges with background surfaces
• Heavy: perimeter outline

## Give It a Try

Keep going with the drawing subject you've chosen and try a 3D isometric drawing. Share what you've got with the rest of the class and we'll give you feedback.
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