Purpose: To further understand more of the advanced model editing tools and techniques.

Objective: Review the Extrusion Along Curve, and Draw Cubic by CV’s Tools.

Extrusion Along Curve

Using the Extrusion Along Curve function we can create a surface or polygon mesh by extruding a profile curve along a guide or rail curve. The following example will require 2 primitive circles. One Circle will become our final Polymesh; the second Circle will act as a “profile” in which we shape the first circle into our finished product – a torus prefabricated to a shape of our own design.

  • Get > Primitive > Curve > Circle
  • Rotate the curve 90 degrees (hold shift while rotating to snap)
  • Set the Radius to about 2
  • Get > Primitive > Curve > Circle (do not rotate this one)
  • Set the subdivisions to 8
  • Set the Radius to about 0.25
  • Enable Point Selection and in the Front window select the top and bottom 3 points (hold shift to select multiple points)

  • Press X to enable scaling and drag them down like so:
  • Press T to return to Point selection mode and select the top and bottom points to scale them down like so:

  • Return to Point selection mode, and finally, select the left and right side points and scale them inwards like so:

Now that we have our regular circle and our “profile” circle created. We can extrude along the curve of our profile circle to create a torus of our own design.

  • Press spacebar to return to object select mode, and make sure the profile circle is selected
  • From the very top Menu bar under Models/Create, select Poly. Mesh > Extrusion Along Curve

  • Your mouse icon will now display the word PICK underneath the mouse pointer. PICK the first circle we created. This will extrude the circle to match the second Profile circle that we created.

The Extrusion Along Curve is a very simple but highly effective tool to remember in modeling. We will return to this later in the course. For now, spend a few more minutes on a new scene to see what other interesting shapes you can create from a profile Circle using Extrusion Along Curve.

TIP: If we wish to edit the Polymesh we create from a profile extrusion, select the profile circle and try scaling it to affect the Polymesh. The profile retains a relationship with the final Polymesh even after the extrusion has taken place – allowing us to continue the modification of our Polymesh via the profile circle.

Draw Cubic By CV

Say we wanted to utilize the Extrusion Along Curve technique on an object that is not based on a primitive circle, but is rather based entirely on a 2D line drawing of our design.

Draw Cubic by CVs allows you to place (or draw) control points (also known as control vertices or CVs).

The curve does not pass through the locations you click but is a weighted interpolation between the control points. As you add more points, the existing knot positions may change but the point positions do not.

  • Create a New Scene and select Create > Curve > Draw Cubic By CV’s
  • In the Front View, draw a shape by clicking several times while moving your mouse:

Note: Observe the interpolation effect of the line between any 2 points as you move along.
Tip: At any time you can edit the CV’s (or their handles) by pressing (M)

Now that we have created a curved line profile that is appealing, let’s use it to create a model mesh:

  • Get > Primitive > Curve > Circle and set the Radius to 0.25.
  • Rotate the Circle to -90 degrees on the Y axis (remember to use hold shift while dragging the Y rotator handle – which is green)

Note: Keep in mind, if we wanted to, we could modify the points of this profile Circle as we did before, but for now we will stick with a simple circle.

Again, let’s extrude along the curve of the circle to match our profile shape.

With the circle still selected (return to Object selection mode if preferred):

  • From the very top Menu bar under Models/Create, select Poly. Mesh > Extrusion Along Curve and PICK the profile shape you created with the Draw Cubic by CV’s tool.

Presto! Our very own custom pipe or wire has been created with very little effort required.

However, what if we find that the profile radius of our newly created pipe is too large? Simply select the circle profile object, press (T) to enter point selection mode, select all the points and press (X) to drag the inner yellow scale box (origin point for uniform scaling) inwards. You will notice this has an immediate effect on our 3d model.

The same editing technique can be applied to our line 3D shape. But at the moment, the line is inside our 3d object so it will be hard to select. Open the Explorer window (8) and select crvlist. The line will be highlighted white in your Orthographic views. Locate the line in the Front view, and press (M) to edit the line shape. You will again observe that any change made to the line will have an immediate effect on the 3D object.

There are many, many, many advanced features available for Extruding Along Curves – so we couldn’t possibly cover them all here. The best way to learn them is to explore the program and experiment on your own.

For example, with our line still selected in edit mode (M):

  • Right click any CV along the line, and select open/close. This completes or closes the line by joining the start and end CV’s.

Exercise 1

Spend at least 20-30 minutes reviewing these principles: creating profile shapes with either primitive curved circles or custom Cubic CV’s, extruding along curves, and modifying the 3D objects afterwards utilizing the original profiles.

What interesting shapes can you make? Does this technique work on any other Curve primitive shapes? (yes, try a spiral/square combination).

Exercise 2

Write your name in 3D using the Draw Cubic by CV’s Tool. Either use a circle (modified or unmodified) or a square Curve to serve as your “profile.” Remember to create a new profile shape for each new letter you create, and to utilize the open/close option to complete each letter.

  • Feel free to save your work in the Scenes Directory under Haus of Mapping Curriculum Project Path.

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