Workshop 17 Notes

November 25, 2008 Workshop 17 Notes

HAIR

1. SIMPLE CASE. (Techniques developed after those described in The Secrets of the Pros, By Kundert-Gibbs and Dariush Drakhshani, Sybex Inc. 2005) The resulting animation is contained in the scene file hairball.mb.

1. Create a NURBS sphere.
2. With the sphere still selected, choose Hair > Create Hair.
3. In the dynamics menu, select Solvers > Interactive PLayback.
4. Create 100 frames
5. Now give some movement to the sphere, keyframing it in two locations at fame 0 and frame 30, and observe the hair performance.
6. Add keyframed scaling to the sphere surface. Keyframe it at a different scale at frame 60, and observe the hair performance.
7. Add keyframe rotation to the sphere surface. Keyframe it at a different rotation at frame 90, and observe the hair performance.
8. Select the hair and enter the attributes editor for HairSystemShape node (e.g., HairSystemShape1).
* In Clump and Hair Shape, change hairs per clump to 20. (increases strands of hair).
* In dynamics, under Solve, change Stiffness to 0.05 and replay the animation. (lowering the number increases flex in hair).
* In dynamics, under Solve, increase iterations to 6 and replay the animation (increases the iterations per time-step increasing accuracy and render time).
* In dynamics, under Forces, increase drag to 0.1 (indicates drag on hair relative to folicle. simulates friction with air - similar to water). Play the result.
* Under multi-streaks, change multi-streaks to 3 and render the result.

2. ROPE 1 (Techniques developed after those described in The Secrets of the Pros). The resulting animation is contained in the scene file rope1.mb.

1. Draw an ep curve along the negative x-axis, placing points at -12 units, -8 units, -4 units and the origin.
2. Repeat this for the positive x-axis beginning at the origin. Select this second curve, and go to Edit Curves/Reserve Curve Direction. (Or, begin this curve in the reverse direction starting at 12 units, 8 units, 4 units and the origin).
3. Select both curves, and in the Dynamics module, select Hair > Make Selected Curves dynamic.
4. Both hairs are now dynamic under a single hair system.
5. In outliner, select hairSystem1Folices, select the plus sign, open the attribute editor for follicleShape1, set the point lock system to Base in the channels box.
6. Repeat step five for follicleShape2.
7. Playback animation for 60 frames, and the center of the rope should appear to drop below the origin.
8. Goto frame 60, and under Hair select Display> Current Position (this depicts the active dynamic position of the hair.)
9. To visualize the rope, create a small nurbs circle in the x-z axis from the side view window.
10. Ensure that the History option is on. Select the circle and the first curve, and under Sufaces>Extrude, set style to "Tube", result position to "At path", Pivot to "Component", Orientation to "Profile Normal", and Output to Nurbs, and Apply the tool.
11. Repeat this for the second curve.
12. Within the Outliner, select hairSystem1, and then, in the Attribute editor, select the tab for hairSystemShape1.Continuing in the Attribute editor, select the Dynamics tab, and then the Solve sub-tab, and change "Stiffness" to 0.003. Also in the Dynamics tab, under the Forces section, change gravity to 5.
13. In components mode, select the CVs at the origin from the two curves, and goto Hair>CreateConstraint>Hair to Hair.
14. Play 100 frames.
15. From the Hair menu, set Start Position to From Current.
16. In outliner, select hairConstraint1, go to frame 149, and right-clicking on the text, in the Channel box, set the key frame Glue Strength to 1.
17. Now go to frame 150, and right-clicking on the text, set the key frame for Glue Strength to 0.
18. Playback the animation and the rope breaks at frame 150.
19. Select hairSystem1 in the outliner, and in the attribute editor under hairSystemShape1, in Turbulance change Intensity to 0.2

3. ROPE 2 - BEHAVIOR EXTENDED. The resulting animation is contained in the scene file rope2.mb.

1. For the preceding example, select the two cyinder surfaces and goto Edit Group.
2. Make a set of particles at intervals of 2 units each along the positive z-axis.
3. Change to Select by Hierarchy and Combinations.
4. Select the cylinders and then shift-select the instances of the particles.
5. Under the particles menu select instancer replacement. Play back the animation.
6. Select hairSystem1 in the outliner, and in the attribute editor under hairSystemShape1, in Turbulance change Intensity to 1.0 and speed to 4.

4. PARACHUTE. The resulting animation is contained in the scene file parachute.mb.

1. Draw an ep curve along the negative x-axis, placing points at -0 units, -4 units, -8 units and 12 units.
2. Select edit curve/reverse.
3. Go to edit duplicate special, and make 7 copies rotated at 45 degrees each. Select all the curves, and in the Dynamics module, select Hair > Make Selected Curves dynamic.
4. Allhairs are now dynamic under a single hair system.
5. In outliner, select hairSystem1Folices, select the plus sign, open the attribute editor for follicleShape1, set the point lock system to Base in the channels box.
6. Repeat step five for the other seven folicles.
7. Within the Outliner. select hairSystem1, and in the Attribute editor, Under Dynamics tab and the Solve sub-tab, change "Stiffness" to 0.001, and Length Flex to 0.95, and under the Forces section, change gravity to -0.5 (reverse direction).
8. In components mode, select the CVs at the origin from the two curves, and goto Hair>CreateConstraint>Hair to Hair.
9. In outliner, go to hairSystem01OutPutCurves, and selecting two curves at at time, loft a polygon between each pair, using 6 section spans.
10. Within the Outliner. select hairSystem1, and in the Attribute editor, Under Turbulance, Change intensity to 0.5.
11. Play the animation to frame 200.
12. Assign materials from the Phong shader using transparent red and white colors on each alternative polygon surface.
13. Goto frame 0, select all the set of hairSystem1OutputCurves from the outliner, move the up the positive y-axis, and key frame them with the S key.
14. Play the animation to frame 200 with the curves still selected, and use the move tool to move the curves down the y-axis. Key frame them at this location. Play back the animation and see the result.

5. SIMPLE ON-LINE TUTORIAL EXAMPLES { WE WILL SKIP THIS IN THE WORKSHOP

1. Goto Hair/GetHair Examples

6. ROPE 3 WITHOUT A SURFACE (Excerpted in part from on-line help documentation)

1. Create a bspline curve in the front view.
2. In the dynamics module Select Hair > Make Selected Curves Dynamic.
* Click Make Curve Dynamic to turn the selected curves into dynamic hair curves.

To make a curve dynamic

1. Select the curve.
2. Go to the attribute editor and open the attribute for the "follicle shape" (e.g., follicleShape1).
* Change the Point Lock to Tip.
* Under "Dynamics Overrides", select the check-box for "Overrides Dynamics" and reduce the stiffness to 0.05.

To See the Hair

1. Goto Hair/Assign Paint Effects Stroke to Hair
2. Goto the Brush tab/select Screen Width Control and turn it on/Change Max Pixel Width to 9.0