Hello again! Welcome back to your digital art journey.
In our last lesson, we focused on constructing the fundamental 3D forms—spheres, cubes, cylinders, and cones. You learned how to build these "wireframe" skeletons from simple 2D shapes. Today, we're going to learn how to wrap a "skin" around those skeletons to make them look truly solid and three-dimensional.
Our learning outcome for this lesson is to apply cross-contour lines to describe the surface and volume of a 3D form. These lines are a powerful tool for understanding and communicating volume, and they are essential for moving from drawing flat shapes to creating convincing illusions of depth.
Given your background in computer science, you can think of cross-contour lines as being very similar to the wireframe on a 3D model. They are a visual representation of the object's surface topology, revealing every curve, bump, and plane. Mastering this will be invaluable as we move toward the complexities of human anatomy.
1. What Are Cross-Contour Lines?
A cross-contour line is a line that moves across the surface of a form, describing its shape and volume. Instead of just outlining an object, these lines wrap around it, giving our brains the information needed to perceive it as a 3D object in space.
To start, let's get a clear visual definition of what cross-contour lines are and the effect they have. This short, focused video from the Drawsh Studio channel demonstrates the concept perfectly.
Watch the first 1 minute and 23 seconds. Notice how a simple, flat 2D ellipse is instantly transformed into a convincing 3D form just by adding a few carefully placed lines.
As you can see, the lines aren't random; they follow the "rules" of the form's surface. Let's explore that "wireframe" analogy a bit further.
Understanding Cross Contours - Thinking Like a 3D Modeler
The video 'Understanding Cross Contours - Thinking Like a 3D Modeler' by artist Alex Huneycutt makes this connection to 3D software explicit. It's a great way to frame the concept.
First, watch the introduction from 00:00 to 01:00. Then, jump ahead and watch the core demonstration from 04:42 to 05:48. Pay attention to how he calls it 'working as a 3D wireframe' and applies the concept to the basic forms you learned last lesson.
This image shows the idea applied to the forms we constructed in our previous lesson. The lines give immediate information about the curvature and orientation of each object.
2. The Principles of Cross-Contour
To draw effective cross-contour lines, you need to understand three key principles: Curvature, Spacing, and Degree.
Principle 1: Curvature
The curve of the line describes the curve of the surface.
- On a flat plane (like the face of a cube), the cross-contour line is straight.
- On a curved surface (like a sphere or cylinder), the cross-contour line is curved. The more pronounced the curve of the line, the rounder the form will appear.
Principle 2: Spacing (Perspective)
Just like train tracks appearing to converge in the distance, cross-contour lines appear closer together as the surface of the form curves away from the viewer. This effect, a result of perspective, dramatically enhances the illusion of depth.
Let's revisit the Drawsh Studio video for a clear explanation of this perspective rule.
Watch the segment from 03:08 to 04:35. Note the 'train tracks' analogy and how the artist draws the lines closer together near the edge of the cylinder to show the surface turning away.
Principle 3: Degree (Ellipses)
On cylindrical and spherical forms, the cross-contour lines are ellipses. As you learned when constructing cylinders, the degree (or "width") of an ellipse tells us how it's oriented in space.
- A wide ellipse (closer to a circle) looks like it's facing us.
- A narrow ellipse (thin and flat) looks like it's turned away from us.
When drawing cross-contours on a form like a cylinder or a sausage, the degree of the ellipses will change as they move along the form's length, giving us crucial information about how it's bending in 3D space.
Lesson 2: Contour Lines, Texture and Construction - Drawabox.com
The concept of changing ellipse degree is fundamental. The Drawabox.com lesson on contour lines explains this rule very clearly. We will use this resource for a major exercise later, but let's read the theory section first.
Please read the sections titled 'Our contour lines' degrees' and 'The effects of bending'. Focus on understanding the core rule: ellipses generally get wider as they are further away from the viewer, and the form's bending also affects their orientation.
3. Practice Exercises
Time to put these principles into practice in Procreate. We'll start with the simple forms and then move to a more complex organic shape.
Exercise 1: Contouring the Basic Forms (15 minutes)
Let's begin by applying cross-contours to the cubes, spheres, and cylinders you already know how to build.
Cross Contour Drawing - The Definitive Guide (2024)
The article 'Cross Contour Drawing - The Definitive Guide (2024)' provides a perfect first exercise for this.
Read just the section titled 'Cross Contour Line Drawing Exercise 1: Simple Forms'. This will set up our first practical task.
Your Task:
- Open Procreate and create a new canvas.
- Using the construction methods from our last lesson, draw several cubes, spheres, and cylinders.
- Create a new layer on top of your forms.
- Now, draw cross-contour lines over each form:
- Cube: Draw a grid of straight lines on each visible face. Make sure these lines follow the perspective of the cube's edges.
- Sphere: Draw lines of "longitude" (from top to bottom) and "latitude" (wrapping around).
- Cylinder: Draw ellipses wrapping around the form's body. Remember to vary their degree and spacing! Also, draw straight lines running down the length of the cylinder.
Exercise 2: The "Sausage" Drill (20 minutes)
Now let's tackle a form that can bend and twist in space. The "sausage" exercise from Drawabox is a classic drill for developing an intuitive feel for volume. This is a direct precursor to drawing arms and legs.
Lesson 2: Contour Lines, Texture and Construction - Drawabox.com
This next exercise is more intensive but incredibly valuable. We'll use the Drawabox article from before as a detailed guide.
Read the article carefully from the beginning down to (but not including) the 'Mistake' sections. The key steps are: draw the sausage form, draw the central 'spine', and then add the contour ellipses or curves, paying close attention to their degree, spacing, and alignment with the spine.
Your Task:
- On a new page in Procreate, fill it with sausage forms of various shapes and orientations.
- For roughly half of them, draw the full contour ellipses, as if you have X-ray vision. This helps you understand the whole structure.
- For the other half, draw only the visible contour curves. Try the 'overshooting' technique mentioned in the article to help maintain the sense of curvature as the line reaches the edge.
- Focus on the process and the feeling of describing a 3D volume with your lines. Repetition is key here.
Conclusion
Great work today. You've learned how to take a simple 3D structure and make it feel solid and tangible by describing its surface with cross-contour lines. This skill forces you to think three-dimensionally at all times and is a massive step forward in your artistic development.
Key Takeaways:
- Cross-contour lines wrap around a form to describe its volume, much like a wireframe on a 3D model.
- The curvature of the line communicates the curvature of the surface.
- The spacing between lines creates depth through perspective; lines get closer as the surface turns away.
- The degree of elliptical contour lines tells us about the form's orientation in 3D space.
In our next lesson, we'll learn to break down complex reference objects into a combination of simple geometric forms. Now that you can build simple forms and describe their surfaces, you're ready to start identifying these forms in the world around you. This is the final step before we can start assembling them into the complex structure of the human figure.