Using Curve, Circle and Rectangle Tools

Realsoft 3D supports three kinds of geometric objects:

  1. Analytic

  2. NURBS

  3. SDS

Analytic objects are memory efficient, fast to render and they perform fast Boolean operations. Analytic means that the surface and other geometric properties of an object are defined accurately using a mathematical equation. For example, an analytic sphere is defined by two attributes: center and radius. The problem with analytic objects is that due to their minimal definition, their geometry is very rigid and doesn't allow you to represent arbitrary freeform shapes.

Various Analytical objects - Polyhedron with boolean holes, cylinder, cube and cone

NURBS (Non-Uniform Rational B-Spline) has become a standard curve and surface representation method in computer graphics. NURBS objects are slightly slower in Boolean operations but they can be used for representing freeform shapes easily, because a NURBS surface is defined by a set of freely editable points. One powerful feature of NURBS surfaces is the ability to cut away part of the surface with trim curves. A NURBS surface always has a regular, 'rectangular' topology: It consists of a grid of connected rectangular patches. Branching surfaces can be modeled by joining several surface patches together, and cutting with trim curves creates holes.

NURBS object with trim curves defining edges

SDS (=Subdivision) surfaces allow arbitrary polygonal and smooth freeform shapes. The major advantage of SDS surfaces is their free topology: A single SDS object can include branches and holes. Therefore, they are very suitable for modeling organic shapes, human figures, etc.

The toolbar or Realsoft 3D includes a specialized tab for each of these three object types. You can find basic geometrics shapes from each tab. You can also use so called unified toolset to create geometric objects. The unified toolset can create all geometry types described above, and even more: the four general purpose tools have a large number of sub options. By combining the sub options, you can access hundreds of different tools.

SDS object - created from an SDS cube

The default toolbar does not include the unified tools, but you can add the tools to your program interface using the Customization/Available Objects pull down menu.

Unified creation tools

You can activate these tools also from the Tools/Unified pull down menu. The menu contains four basic creation tools: Curve, Sphere, Circle and Rectangle. With these four tools you can create all basic geometric shapes with a freeform, spherical, circular and rectangular shape.

Using the Rectangle tool

The unified Rectangle tool allows you to create various objects with a rectangular shape:

For example, to create an analytic rectangle:

1. Activate the unified Rectangle tool (Pull Down Menu/Tools/Unified/Rectangle)

Unified Rectangle tool activated. The tool control bar shows you the unified Rectangle tool specific options
Select Analytic

2. Click the Type field and Select Analytic.

3. Now enter two points defining two opposite corners of the rectangle through the view window.

An analytic rectangle is very memory efficient and a fast object to render. It can be used for representing planar surfaces such as walls, floors, etc. However, it cannot be bent nor twisted. Analytic rectangles can only represent flat planar surfaces.

A rectangle defined by entering two opposite corner points

If you need to create a rectangle which can be deformed (for example, which can contain bumps in its geometry), you should create a rectangular NURBS mesh. This can be done as follows:

1. Activate the unified Rectangle tool.

2. Set the Type field to Nurbs.

Set the Type field to Nurbs

Now the tool control bar shows you options specific to NURBS meshes. For example, there are two resolution fields, which define the number of control points for the rectangular mesh.

3. Set U to 6 and V to 4 to create a Nurbs mesh with 6x4 control points.

Resolution set to 6x4

4. Enter two points through the view window to create a NURBS rectangle.

A Nurbs mesh consisting of 6x4 control points

The trim curve feature makes it possible to remove a part of a Nurbs surface. For example, to drill a rectangular hole to the mesh:

5. Make sure the Nurbs mesh is selected and activate the unified Rectangle tool. Set Class to Trim Curve and click two points over the Nurbs mesh to define a rectangular trim curve.

NURBS mesh with a rectangular hole

To create an analytic cube:

1. Activate the unified Rectangle tool, set the Type field to Analytic and set the Extrude option.

Options for creating an analytic cube

The Filled option is set by default. It means that the cube will be a solid one with 6 faces. If Filled is cleared, the cube will become hollow and without the front and back covers.

2. Define two opposite corner points through the view window to define the base rectangle. As soon as you enter the second point, the unified Rectangle tool starts to outline an apex point and the object looks like a pyramid. Don't define the third point. Just select Accept from the view's popup menu or from the tool control bar. A cube is created.

Analytic cube

If you want to create a pyramid instead of cube, enter three points and then press Accept. If you want to create a pyramid woth a flat top, enter four points.

In other words, the type of the object depends on the number of points entered. If only two points are entered, the result is a cube. Three points define a base rectangle and an apex (i.e. pyramid). Four points define a base rectangle and a top rectangle i.e. cut pyramid.

Three different objects achieved by using the Extrude option

Using the Circle tool

The unified Circle tool allows you to create:

To create an analytic cylinder:

1. Activate the unified Circle tool.

2. Set Type to Analytic just like you did with the unified Rectangle tool and select Extruded from the Extrude gadget.

Options of analytic cylinder

3. Click two points through the View window and select Accept. A cylinder is created.

If you accept the tool after three points, the result is a cone. Entering four points (center and radius for the bottom and top disks) creates a cut cone.

Note: the Define field allows you to control the creation method. For example, a circle can be defined by entering three points on it, by defining one center and one circle point or by defining a rectangle, which represents the bounding box of the circle.

Shaping a cylinder

To create a circular Nurbs curve:

1. Activate the unified Circle tool.

2. Reset the Filled option (we don't want to create a surface).

3. Set the number of points defining the curve to the Points field, for example 8.

4. Enter two points through the View window to define the center and the radius for the curve.

Options for a circular Nurbs curve

Using the Curve tool

The unified Curve tool can create:

To create a smooth NURBS curve:

1. Activate the unified Curve tool

2. Enter a number of points through the view window. At your last point, select Accept from the toolbar or from the popup menu of the view window.

Drawing a smooth Nurbs curve

To create a polygonal curve:

1. Activate the unified Curve tool.

2. Set Order to Polygonal. Then define a desired number of points through the view window and click Accept.

Polygonal curves have sharp edges - quadratic and cubic curves use control points which are interpolated through to create a smooth curve. You can control the sharpness of these curves by adjusting the weights of each control point.

Polygonal curve

To create an analytic polyhedron (extruded polygon):

1. Activate the unified Curve tool

Options for a polyhedron

2. Set Type to Analytic and set Extrude. Define a desired number of points through the view window and click Accept.

3. The program starts visualizing the apex of a pyramid-like shape. A new mouse click would create such a pyramid, but choose Accept instead. In other words, Accept twice to create a polyhedron - one Accept + a new click creates a pyramid shaped polyhedron.

Polyhedron created

Using the Pen option to create surfaces

The unified curve tool supports a Pen option, which allows you to create Nurbs surfaces interactively. Use the pen option this way:

1. Draw a Nurbs curve as instructed earlier in this tutorial

2. Make sure the curve is selected and activate the unified Curve tool.

3. Select a suitable pen type from the pen gadget of the tool control bar.

4. Draw the new Nurbs curve. The program shows you the resulting surface as you enter the points of the new curve.

The following pen options are available:

None. If this is set, pen is though to be an infinitely small point and a curve is created.

Plain curve

Rail. If this option is set, the selected pen curve will be swept along the curve drawn. The pen object is not rotated while sweeping.

Rail pen

Sweep. This option is the same as the previous one except that the pen object is rotated according to the curvature of the curve drawn. For example, by using a circle as the pen object, one can create a circular tube.

Sweep pen

Rotate. This method uses the pen object as an axis and rotates the new curve around it.

Rotate pen

Using unified tools for mapping materials and for 3D painting

The unified tools can also create material mapping objects through the Class option. For example, we can use the unified Rectangle tool to map the wood material to a sphere using the Parallel mapping method.

To do this:

1. Create a test object, for example a sphere.

Class option of the unified Curve tool

2. Activate the unified Rectangle tool and set Class to Parallel Map. Now the control bar contains a list of available materials. Select wood and define two opposite corner points through the view window.

The Parallel map option of the unified Rectangle tool

A parallel mapping object is created. You can render the view window to make sure the created material mapping object works.

Note that there are also many special purpose tools for creating mapping objects. You can find them from the Materials tab of the main toolbar, for example. If you need to map many materials, you might find the specialized tools more productive.

Similarly, you can find the 3D painting tools through the unified tool interface, although the Materials section of the toolbar contains more specialized painting tools.

Wood mapped sphere