Spline and NURBS Modeling
Spline and NURBS (Non-Uniform Rational B-Splines) are essential tools in 3D modeling, particularly useful for creating smooth and organic shapes like car bodies, architecture, and industrial designs. Unlike polygon-based modeling, spline and NURBS modeling uses curves to define shapes, which are mathematically smooth.
Introduction to Splines and NURBS
A spline is a smooth curve defined by control points. In Blender, splines can be either 2D or 3D. Common spline types include Bézier curves, which are widely used for animations and complex smooth shapes.
NURBS are a special type of spline that offers more control over curvature. They allow for creating both smooth and sharp edges in a continuous form. NURBS can handle complex surfaces with precision, especially useful for mechanical and architectural modeling.
Types of Splines in Blender
Blender supports several types of splines for curve modeling:
Bézier Curve: Offers manual control over handles for sharp or smooth curvature adjustments.
NURBS Curve: A smooth curve where control points define the curve's shape.
Poly Curve: A curve made of straight segments, often used for path animations.
Working with Bézier Curves
Step-by-Step Guide:
Adding a Bézier Curve:
Open Blender, and in Object Mode, press Shift + A → Curve → Bézier Curve.
Adjusting the Curve:
In Edit Mode (Tab), you'll see the curve's control points and handles.
Select the control points (press A to select all or B for box select), and use G to move them, R to rotate, and S to scale them.
Controlling Handles:
Each control point has two handles that influence the curve's smoothness.
Select the handle with LMB and move it with G. You can rotate (R) or scale (S) the handle to control the curve's shape.
Extruding a Bézier Curve:
After shaping the curve, go to the Properties Panel on the right, then click the Curve Object Data Properties (curvy icon).
Under the Geometry section, increase the Extrude value to give the curve a 3D shape.
Working with NURBS Curves
Step-by-Step Guide:
Adding a NURBS Curve:
In Object Mode, press Shift + A → Curve → NURBS Curve.
Modifying NURBS Control Points:
Switch to Edit Mode and manipulate the NURBS control points similarly to Bézier curves. NURBS curves automatically smooth the curve between points.
Converting NURBS Curves to Surfaces:
To create a surface from a NURBS curve, you need multiple curves. Duplicate the NURBS curve (Shift + D) and move it along an axis (e.g., Y-axis with G → Y).
Once you have several curves, switch to Object Mode, select all curves (A), and then use F3 to search for "Loft" or use Object Menu → Convert To → Mesh from Curve.
Working with NURBS Surfaces
NURBS Surfaces work similarly to NURBS curves but are used for creating complex 3D surfaces directly.
Add a NURBS Surface: Press Shift + A → Surface → NURBS Surface.
Adjust the surface by manipulating the control points in Edit Mode. These surfaces allow for smooth and organic shapes, often used for industrial designs, automotive models, etc.
Converting Curves to Mesh
After designing with curves, you can convert them into a mesh for further detailing.
In Object Mode, select the curve and press Alt + C → Convert to Mesh from Curve.
Exercise: Creating a Wine Glass with NURBS
Objective:
In this exercise, you'll model a smooth, symmetrical wine glass using NURBS curves.
Step-by-Step Instructions:
Add a NURBS Curve:
Press Shift + A → Curve → NURBS Curve. This will serve as the profile of the wine glass.
Shape the Curve:
Go into Edit Mode by pressing Tab.
Move the control points to form the profile of the wine glass. The top point will represent the rim, the middle points the body, and the bottom point the base.
Remember to keep the shape simple at first. You can refine it later.
Convert the Profile into a Surface:
Once you're satisfied with the curve, go to Object Mode and in the Modifiers panel (wrench icon), add a Screw Modifier.
Set the axis to the Z-axis and adjust the angle to 360° to create the full glass shape.
Fine-Tune the Glass:
After spinning the curve, you'll have a glass-like shape. Enter Edit Mode again and tweak the control points to refine the profile.
Adjust the thickness using the Extrude option under the Geometry tab in the curve's properties.
Apply Material:
Go to the Material Properties tab and add a glass shader to simulate the appearance of glass.
Render the Scene:
Set up a simple scene with lighting, a camera, and render the final result.
Summary:
In this lesson, you've learned the basics of spline and NURBS modeling in Blender. You've seen how to work with Bézier and NURBS curves, as well as how to extrude and convert curves into 3D surfaces. The exercise helps you understand the practical application of these tools by creating a wine glass, giving you a great start in organic and industrial design.