Building A NURBS Hand

This tutorial was written with specific command references and screenshots from Rhino 3D, but the same steps can be followed in other NURBS modeling packages, if you don't mind using trims and blends in your characters. (The workflow described here is also how I did the hand in Alias Power Animator for the fetus animation, but would not be how I would work in current versions of Maya or Softimage, where I would use Global Stitch or SCM instead of trims and blends.)

1. Draw two curves in the front view, representing the left and right sides of a finger. Turn on Snap to get the top ends of the curves aligned at the center axis.

2. Draw two move curves, this time in the side view, representing the front and back of the finger. Don't worry about a finger nail - we'll add that as a separate surface.
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3. Make the perspective view or top view active, so that you can see all 4 curves at once. Surface>Loft together the four curves. (Normal Style is fine. Rebuild with about 10 or 12 control points. Be sure to check "closed.")

4. Make a new layer, and move your construction curves away into that layer. Turn off that layer in the Edit Layers panel, to get the curves out of the way.

5. Show points on your finger model, and edit the shape as needed. You might (or might not) want to use Curve>Point Editing>Insert Knots to add more rows of points, for more control over the shape.

6. Zoom in on the tip of the finger in the front view, and draw 4 curves. The left and right curves should represent the edges of the finger nail.

7. Use "Proj" (or Curve>From Surfaces>Projection) and select the 4 curves, and press enter. Then select the finger object and press enter.

8. Select the finger, and "ghost" it, using the Ghost icon in the Layer toolbox.

9. In the right or perspective windows, you can now see that there are 3 sets of curves. The set of curves you drew is in the center, and there are curves projected onto the front and back of the finger. (The front window doesn't show you this, because they are all lined up with eachother along the depth (Y) axis.)

10. The only curves you need are the ones projected onto the back (fingernail) side of the finger. Select and delete the other two sets.

11. Loft together the 4 curves to make your fingernail. (Turn off the "closed" check-box.)

12. If you want, you can show points and edit the shape of the fingernail.

13. Move the construction curves into the construction curves layer.

14. Now we need to make copies of the finger, and scale and position them in space. This is much easier to get right if you have some reference. Click here (this link defaults to open in a new window) to download a reference picture of a hand, or use your own hand or another picture.

15. Put your reference image into the front window with View>Background Bitmaps>Place. To make your reference easier to see in different windows, draw a set of curves that trace all the key contours of the reference image.

16. Remove the image. Put the curves you traced into their own layer for easy showing and hiding. Ghost the reference curves.

17. Use the ghosted curves as reference in copying, rotating, and scaling copies of your finger model.

18. To crop off the lower third of the thumb, use Surface>Rectangle>Cutting Plane to slice mark the location, then Edit>Trim.

19. In the front view, draw 5 curves as shown to the left, to make the palm. They all start coming upwards from the wrist, and all end pointing at the base of the thumb.

20. Make a duplicate copy of the set of curves, so that one set of curves defines the front of the hand, and the other set defines the back.


21. Show points on the curves, and move points in the right view to add curvature to the hand.

22. From a perspective view, loft together all of the curves. Pick them in order going around the base of the wrist. Make sure "closed" is checked, and resample to a size that looks good when you "preview."

23. Draw a set of 4 curves in the front view, as shown to the left. There is one curve around the base of each finger. The curves are close together, but do not intersect.

24. Also in the front view, select the 4 curves, enter "proj," and pick the palm to project onto.

25. Put the 4 curves you drew into a hidden layer, to get them out of the way. (But keep the 4 new 3D curves that were projected onto the hand.)

25. Choose Edit>Split, with the projected curves as the cutting objects. You will not see much of a difference after this command, but it has split the hand into 5 parts: the main piece of the palm, and the 4 little sections at the base of the fingers.

26. Select and delete the 4 pieces that are now separate objects, so that what's left looks like the figure to the right.

27. Depending on how you built or fit together the fingers with the palm, the base of the fingers might need to be cut shorter so that there is some empty space for the transition. If needed, you could cut the fingers the same way you cut the thumb in 18, or you could draw one arching curve, project it in the front window, and then trim the fingers with the projected curves.

28. Use "SrfBlend" (Surface>Blend) to build blends between the middle finger and the opening in the hand beneath it. Start by picking the curve at the trimmed hole in the hand. Make sure you have picked all of it, even if it is in 2 or 3 pieces. Then pick the curve at the base of the finger, also being sure to pick all parts of the curve. Typing "A" for "automatic" should get them lined up without a lot of trouble.

29. Repeat the command for the other fingers and the thumb, so that your hand looks like the one on the right.

30. Use Edit>Join to turn all of the surfaces into a solid. (You can actually leave out the fingernails, it won't matter, but joining guarantees a smoother transition between the blends and the other geometry.)