procedure and tools used for design 

New Sketch Curve Options

Curve Degree

Choose from 1, 2, 3, 5, or 7.

Tolerance

Determines how closely the curve tries to mimic the cursor movement.

Maximum Spans

Together with the curve degree, determines the number of points that are laid down for the curve.

Pivot Position

Specifies the initial position of the curve's pivot points (both rotation and scaling).

Origin – The pivot points are located at (0, 0, 0).

First CV – The pivot points are located at the position of the first CV, that is, the start of the curve. This is the default.

Last CV – The pivot points are located at the position of the last CV, that is, the end of the curve.

Curve center – The pivot points are located in the middle of the curve, based on arc length. (This is the same position as Snap to Center in the Curve Snap Options box.)

Bounding box center – The pivot points are located at the center of the curve's bounding box.

Draw curves by placing CVs

1. Choose Curves > New Curves > New CV Curve.
2. Click in view windows to place the CVs of the new curve, or type coordinates for the CV locations.

   For a degree 3 curve (default), the curve will only appear after 4 CVs have been placed.

   Note:

   The general rule is that a curve of degree m requires m+1 CVs before becoming visible. To see the curve sooner, turn on Progressive Degree in the options box.

   Tip:

   The first CV in the curve is shown as a square and the second as a “U” instead of a cross. This helps show the direction of the curve.

   
3. Choose the tool again to start another curve.

Draw curves by placing edit points

1. Choose Curves > New Curves > New Edit Point Curve.
2. Click in view windows to place the edit points of the new curve, or type coordinates for the CV locations.
   
3. Choose the tool again to start another curve.
   Tip:

   This tool is useful when you want to create a single span curve from two endpoints.

   Tip:

   You can continue drawing curves between view windows. For example, click the first point in the Top window, click the second point in the Back window, and so on.

Connect two points with a straight curve

1. Choose Curves > New Curves > New Edit Point Curve.
2. Click the first point. You can use curve snapping to snap the point to a curve or surface.
3. Click the second point.

The new curve is a straight line between the two points. To make the curve tangent or curvature continuous, use Object Edit > Align > Align to align the new curve with the existing objects, or BlendCrv Tools > Blend Curve Create.

Create curves-on-surface by projecting curves onto surfaces

The Project tool lets you specify and change the projection direction from within the tool, as described in the workflow below. By default, the tool projects along the view vector of the current window (that is, the direction the camera is looking at). You can also use an external reference vector to specify the projection direction.

1. Choose Surface Edit > Create CurvesOnSurface > Project .

   The control window opens.

2. Make sure that Create is set to Curves on surfaces.
3. Select the surface(s) on which you want to project a curve, then click the Go button.

   The surfaces turn pink.

   
4. Select the curve(s) to project then click the Project button.

   The curve is projected along the View vector of the active window, by default. A curve-on-surface is created on the surface(s).

   
5. Change the view in the Perspective window, then click the Refresh View Vector button. (You can also change the view to that of a different window by clicking in it).

   The curve-on-surface updates according to the new view vector in the Perspective window.

   
6. In the control window, choose a different vector option such as X, Y, Z, or Normal.

   The curve-on-surface updates.

   
7. In the control window, choose the Picked vector option, then select a vector object.

   The name of the vector appears in the Picked Vector field. The curve-on-surface updates according to the picked projection vector.

   
8. Exit the tool (for example choose Pick > Object).

   The control window disappears.

9. Choose Object Edit > Query Edit and select the curve-on-surface.

   The Project tool control window opens. You can modify the options and watch the curve-on-surface update. This only works if the curve-on-surface was created with construction history.

Trim a surface

You can trim more than one surface at a time, using one or more projected curves or intersecting surfaces.

Trim or divide a surface by projecting curves on surfaces

1. Choose Surface Edit > Trim > Trim Surface .
2. In the control window, turn on 3D Trimming and choose Normal under Vector Options.
3. Select all the surfaces you want to trim. Hold down the  key to pick more than one surface, or use a pick box.
4. Select the curves you want to project onto the surface to create trim curves (curves-on-surface). If the desired curves-on-surface are already present, you can skip this step.
   

1. Click on the regions of the surfaces that you either want to keep or discard. (Regions are areas delimited by curves-on-surface). If the trim regions are spread across multiple surfaces, you can box-select them.
   

   Crosshairs appear on the selected regions. To move a crosshair, click it and drag.

   If those region selectors appear too large or too small on your geometry, you can adjust their size by using the Region Selector U Size and V Size sliders in the control window.

   Tip:

   You do not have to click a “visible” part of the surface (such as an isoparametric curve). Clicking anywhere inside the surface edges will also work.

2. At any time, before performing the next step, you can change the vector option in the control window to change the direction of projection.

   The curves-on-surface update.

   Note:

   If you choose Picked, you must then pick a vector object along which to project.

   Note:

   If you choose View, you can project different curves along different view vectors. However, if you then click Refresh View Vector, or select a different vector option, all curves-on-surface update to match the current projection vector.

3. Click one of the buttons: Keep, Discard, or Divide, depending on the type of operation you want to perform.

   Keep: Keeps the regions selected in step 5, and discards the rest.

   Discard: Discards the regions selected in step 5, and keeps the rest.

   Divide: Divides the selected regions from the others (making separate trim surfaces) but keeps all the regions.

   
4. After the trim operation has been performed, you can undo it by clicking the Revert button.

   You are left within the tool with all your selections intact, so you can adjust your selections and trim again.

    

create a surface inside four boundary curves or corners (Square)

Use Square to create a surface by blending inward from a combination of four free curves and/or corners.

Create a new square

1. Choose Surfaces > Boundary Surfaces > Square  .
2. Click the boundary curves, or snap corner locators to existing geometry, in clockwise or counter-clockwise order.

Notes

• Combinations of curves and corners you can use:
  
• If you mix curves and corners, you must click the curves first.
• After the surface appears, you can move a corner locator by dragging it.

Create a new surface by blending four boundary curves (or curve segments)

1. Choose Surfaces > Boundary Surfaces > Square  from the tool palette.

   The Square Control window appears.

2. Click the first boundary curve.

   or

   

   Click a point on the curve (to use as a corner) by holding down either the  (Windows) or  (Mac) key or the  and  keys.

   • You can use free curves, curves on surface, isoparametric curves, and/or trim edges.
   • To maintain continuity with another surface, you must pick an isoparametric curve or trim edge on that surface, not a construction curve used to create that surface.
   • You can use a segment of a longer curve. The Square tool will use the section of the curve bounded by the other curves you click.

   or

   Click a grid point (to use as a corner) by holding down the  key.

3. Click the remaining curves and/or points (corners) in clockwise or counter-clockwise order.
   
   • You can select either four curves, four corners, one corner and two curves, or two corners and one curve.
   • If you select both curves and corners, you must select the curves first.
   • You can only use a snapping mode to select the first corner.
   • If two adjacent boundary curves do not intersect, the Square tool displays an error in the prompt line. Otherwise, the surface is built.
4. Move the corner locators (if any) by clicking them and dragging to change the position of the corners.
   
5. Use the options in the Square Control window to set the continuity you want at each edge (see below).

Use the tangent angle manipulator

This manipulator appears when you set an edge to Tangent Angle in the Square Control window (see below).

• Click an axis line to set the tangent angle to 0, 90, 180, or 270 degrees.
• Click an arc, then drag the mouse left and right to change the angle value, or type a number to set the value exactly.
• When you are finished, click the Go button.

Edit the construction history of a Square surface

1. Pick the surface you want to edit.
2. Click the Square icon, or choose Surfaces > Boundary Surfaces > Square from the tool palette.

   The Square Control window appears.

3. Use the curve modification tools (in the Transform, Curve Edit, and Object Edit palettes) to reshape the curves used to create the surface, and use the Square Control window to change the surface creation options.

 

Align Options

Note: The word "curvature", used on its own, refers to both G2 and G3 curvature.

Continuity

Continuity level between the aligned geometry: G0 Position, G1 Tangent, G2 Curvature, or G3 Curvature.

Lock Position Row

For G1, G2, and G3 continuity alignments, locks the position of the aligned edge CVs to prevent them from moving as you change options.

Alignment Type

Edge – This option is the default and provides alignments for all surfaces when a vector constraint is not used. This includes the alignment of a surface to a surface edge, isoparm, or curve-on-surface (CoS).

Project – This option aligns an edge to a surface by using a projection vector (along the current view by default). It is not necessary to have a curve-on-surface already on the surface to align to it. The curve-on-surface is created automatically.

Note:

If Project is selected, a Vector Options section appears to let you define a vector. The default vector direction is based on the current view.

U/V – This option only appears when aligning a curve to a surface.

The curve is aligned to either the U or V direction of the surface.

Vector – This option only appears when aligning a curve to a surface.

The tangent and curvature alignment is defined by the tangent plane to the surface at the point of contact, and the direction of the vector specified through Vector Options. That is, the tangent and curvature CVs on the curve are only allowed to move in the direction of the vector. This is the equivalent to creating a curve-on-surface on the surface, and aligning the free curve to it.

If the vector is set to View, the shape of the curve in the given view remains the same through the alignment, while maintaining the desired level of continuity with the surface.

Vector

This checkbox is only available when aligning a surface to another surface with Alignment Type set to Edge and Continuity set to G1 Tangent or G2 Curvature.

When Vector is checked on, positional continuity is achieved first, then the tangent and curvature CV rows are constrained to move along the selected vector. (See the Vector Optionssection.)

Tangent Balance

This option is only available when Continuity is set to G1 Tangent, G2 Curvature, or G3 Curvature and the following conditions apply:

• Both the Input and Master are surfaces
• You are aligning to a natural boundary (not a trim edge or curve-on-surface)
• Outer edges are both set to Edge Align

When Tangent Balance is checked on, the CVs of the tangent row are adjusted so that the ratio of the start and end tangent lengths on the Input surface matches that of the Master. If G2 Curvature or G3 Curvature is on, the same applies to the respective curvature row CVs (second and third rows from the edge). The inside CVs are also adjusted so that the Input’s hull (for the tangent and curvature rows) mimics the shape of the Master’s.

Tangent Balance is off.

Tangent Balance is on. The hull shape of the Input reflects that of the Master.

The tangent and curvature lengths can be scaled in a proportional way so as not to change the shape of the Input surface, by using the Tangent Scale, Curvature Scale, and G3 Scale sliders (or corresponding manipulators). These sliders are only available when Tangent Balance is on, but retain their values if Tangent Balance is toggled off then on again.

 

Horizontal/Vertical (Zebra stripes)

• Quick to use, and acceptable accuracy for concept development. Mostly used to check continuity between surfaces.
• Reflects a spherical environment with black and white (or rainbow) stripes mapped onto it – which is never visible in the scene. When the view is tumbled, the reflections move across the model and can be positioned where you want to analyze the surfaces.
• The user only has control of the number of stripes (Repeats), and a choice of 'Horiz' and 'Vert' orientation.
• The spherical environment and the eyepoint are fixed relative to each other. When the view is tumbled, the reflections of the stripes move across the model and can be positioned where you want to analyze the surfaces.