Notes from Workshop 5: February 22, 2007
(Maya Workshop 4: Cloth, Fluid Dynamics, Nurbs (revisited))

I. CLOTH Create a polygon surface;

• Convert polygon to cloth (flat polygon)
• Make a passive cloth object (drum)
• Drop polygon on drum.
• Do this again adding friction to polygon.

 

• Make a horizontal line
• Make a vertical polygon plane
• Convert vertical polygon plane to cloth
• Select vertices on plane
• Transform constrain vertices to verticl line
• Add wind field to move cloth

 

• Loft a polygon between two edges
• Convert to cloth
• Transform constrain cloth to edges.
• Keyframe the movement of the edges

II. FLUID DYNAMICS Select Ocean examples (sailboat)

• Add motor boat to model
• Adjust properties on motor boat locator shape extra attributes (throttle)
• Select boat and add wake, adjust wake properties.
• Add wake to model
• Adjust properties on wake.

III. NURBS

• control vertices (CVs) – on regulating polygon
• edit points – on surface or curve
• hulls – regulating polygon
• isoparms (surfaces) – polygonal object embedded in surface
• surface pathes (surfaces) – sub-surface area

1 Workflow; keep history on, build up from curves

2 Curve direction determined by order of CVs used in its creation and should be consistent when used as a basis for a surface, first and second curve determine U direction.

3 Breakdown of Curves

• Control vertices (CVs) – edit points awar form the curve used to edit its shape
• Edit points (knots) – sit on the curve indicated by an “x”and more direct means of editing curves
• Hulls – straight lines connecting each CV, selectable.
• Spans – area between two edit points, can be added but not directly edited
• Curve point –arbitrary point on a curve, used to detach or align a curve
• Start point – first CV created for the curve
• Curve direction – determined by direction of first to second CV
• Degree – smoothness of the curve 1 (linear), 2, 3, 5, or 7
• Curves require one more CV minimally than its degree

4 CV and EP Cu

5 CV curve tool Create > CV curve tool  creates curve form CV points (try one)

6 EP curve tool Create > EP curvet ool creates curve from edit points (try one)

6.1Pencil Curve tool  Create > Pencil Curve Tool click and drag to draw a line, inefficient, requires many points.

6.1 Editing NURBS curves

• Right click on a curve and select its curve point
• Click on the curve you wish to insert a new EP
• Choose Edit Curves > Insert Knot & a new EP is create and CVs are automatically created to adjust to new point

 6.3 Curve direction: Edit Curves > Reverse Curve (reverses direction)

 6.4 Opening , Closing Curves & Detaching Curves

• Edit curves > Open / Close Curves (to open or close a curve)
• Edit curves > Attach Curves attaches two curves together, order impacts connection
• Detach curve  - select curve, right click on curve and select curve point, and select the edit point “x” that you want to use to detach the curve or click the curve to denote a curve point and then choose Edit Curves > Detach Curves

6.5 Altering Whole Curves: straightening and smoothing

• Select a curve to rebuild
• Edit Curves Menu > Rebuild Curve with dialog box
• Change number of spans and rebuild
• Locking curve preserves length for animation; Edit Curves > Modify Curves > Lock Length; Switch to components mode by pressing f8, select the first CV and press “W” and move the CV, and the curve follows the CV like a piece of string.
• To straighten a curve: Edit Curves > Modify Curves and click on option box next to straighten, deselect the lock curve option and adjust straightness slider to 1 (less values only partially straighten the curve.
• To smooth a curve: Edit Curves > Modify Curves and click option box next to smooth, set the smooth factor to 10 and hit apply.
• To curl a curve: Edit Curves > Rebuild Curves & Checkbox, set the number of spans to 25 (increasing them) and select “Rebuild” OR
• To curl a curve: Edit Curves > Modify Curves and checkbox next to Curl; set curl amount to 2 and Curl Frequency to 1
• To bend a curve: Edit Curves > Modify Curves and check option box next to Bend; set bend amount to 0.15, curve become like a circle.
• To scale a curve: Edit Curves > Modify Curves and check option box next to Scale Curvature; set the scale factor to 0.5 and  max curvature to 1 click Apply.

8. Interactions Between Curves

8.1 Offset: select a curve and select Edit Curves > Offset and check the option box next to Offset Curve; set Offset Distance to 2 and Click Offset (or use channel box to do this interactively)

8.2 Circular 2D Fillets (concave junction between two curves)

8.3 Create two curves to fillet between, right click on first curve and select “curve point” from the marking menu, click the first curve and drag the point to where you want the fillet to arc; right-click the second curve and select “curve point” from the marking menu; shift-click the second curve and drag the point to where you want the fillet to arc; choose  “Edit Curve > Curve Fillet” to create the fillet. (use crossing curves)

9  Creating Surfaces from curves

• Revolve curve: draw curve in front view with thickness; select curve in object mode, under surfaces menu go to box next to Revolve; select axis (y axis) and click “revolve”, press “3” key to increase the smoothness to see the full surface; change shape by changing axis of revolution with show manipulator tool
• Loft surface from curves with ideally equal # of edit points; create two or more curves; select and shift-select curves in order to be lofted; Surfaces > loft; press “3” key to see full surface  geometry
• Planar surface from closed curve with all CVs on same Plane; Surfaces > planar; to make a plane with holes in it, select multiple closed curves.
• Extrude curve from profile curve: create a profile curve (e.g., circle); create a path curve (e.g., an arc); select the circle and shift select the arc; Surfaces> extrude.
• Birail curve: draw two rail curves, draw profile curve that extends from one rail to the other rail using the curve snap “c” key down; choose surfaces > birail > Birail 1 tool; (use Birail 2 tool if you have two profile curves and the Birail 3 tool if you have 3 profile curves)
• Boundary surface; draw three or four curves with intersecting ends (using curve snapping); select all the curves that complete the boundary; choose surfaces > boundary.

10 Surface Curves and Trims

• Drawing on a surface: Select a surface; select Modify  > Make Live or select the magnet icon; choose create > CV or EP Curve > Click points on the surface; press enter; choose Modify > Make Not Live
• Projecting a curve on a surface: Create a surface (sphere); from the front view draw a curve or circle to project onto the surface; Select a surface; Make the front view active; select Edit NURBS > Project Curve on Surface
• To cut a hole from the curve: Edit NURBS > Trim Tool; Select sphere (of previous example); Select part of surface you wish to keep; click “enter”

11 Seeing Tesselation

11.1 With NURBS object selected hit ctrl-a to see attributes; select the second tab (shape tab); click the arrow next to Tesselation; select “Display Render Tesselation” box (shows object geometry to see how it will appear at render time). Advanced option allows you to adjust Tesselation (accuracy)

12 Modifying and Matching Nurbs Surfaces

• Booleans: Difference Operation; create two overlapping NURBS surfaces; choose Edit NURBS > Booleans > Difference tool; Click the object to remain; press “enter”; click object to remove; press “enter” (note history records and allows you to reposition original shapes)
• Rebuilding surface for stitching: select NURBS surface; Edit NURBS > Rebuild; enter 5 in u spans and 5 in v spans (note: spans evenly distributed).
• Attach two surfaces (try on two adjacent NURBS planes): select two NURBS surfaces to attach to each other; Edit NURBS > Attach Surfaces; From menu deselect “Keep Originals”; click Atach (two surfaces become one);
• Fillet two surfaces; place NURBS cylinder on NURBS plane; make x scale and z scale of NURBS plane 5, and translate y value of NURBS cylinder 1; Edit NURBS > Surface Fillet > Circular Filler;

13 Duplicating Surface Curves

13.1 Create NURBS primitive cylinder; Edit Curves > Duplicate Surface Curves and select dialog box; Select the U direction and click “Duplicate”; curves are duplicated and can form basis of new curve.