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Date: Mon, 16 Dec 1996 22:11:50 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Thu, 20 Jun 1996 16:12:46 GMTContent-length: 4199<html><head><title>CS418 Lab 2</title></head><body><h2><!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><!WA0><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/gifs/teapot.thumb.gif">CS 418: Laboratory 2 </h2> <h2> Parametric Surfaces </h2><b> Introduction. </b><p>This exercise is concerned with building surfaces for computer graphics. It willintroduce various types of parametric surfaces. <b><hr>Procedure:</b><p>First you will need to download two files. To do this, click oneach of the filenames shown below. When the text window opens, use the"save as" option to put the file in your own directory. Name each file withthe same name as shown below.<ul><li> <!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/parametric.1995.net"> parametric.net </a><li> <!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/parametric.1995.cfg"> parametric.cfg </a></ul><p>After downloading the files, start DX thenopen and execute parametric.net. Each module (when opened) has a one-lineexplanation of its function. One of the <!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/Parametric.net.gif"> Compute modules </a>performs themainoperation of mapping a 2D grid to 3D coordinates to make the parametricsurface.(The others just produce pi and produce the variables [v,w].)<p><b> <hr> Assignment:</b><p>Quadric surfaces: Modify the Compute in Parametric.net to produce a unitsphere. Use another Compute module to convert the sphere to a"superquadric". That is, if the vector [x,y,z] is a quadric surface, then[x,y,z]^n is a superquadric surface, where the power of a vector justmeans the power of each term. Try values of n from .2 to 10 or so. Youwill need to handle negative values of x, y, and z in the compute. Makethe value of n set by an interactor.The two images below show a sphere modified by n=.3 and n=3 respectively.<p><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/superquad.3.gif"><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/superquad.3.0.gif"><p>Figures of rotation: Modify the program to produce a figure of rotation given bycylinder radius r=abs(w)+.1 where w is the axis of the rotation. Modify the program to produce a figure of rotationwhich approximates the shape of a drink bottle. The bottle should have (at least)a neck, and a body with a bottom.<p>Two bottles modeled in spring 1995 are particularly elaborate.<ul><li> <!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/student.1995.gifs/jh32.bottle.cs418.gif">A juice bottle.</a><li> <!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/student.1995.gifs/medcoke.gif" >A Coke bottle. </a></ul><p>Bottles modeled in 1996.<ul><li> <!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/student.1996.gifs/rosenberger.2.96.bottle.jpg">A beer bottle </a><li> <!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/student.1996.gifs/heitmann.lab2.bottle.gif">A vase </a><li> <!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/student.1996.gifs/demers.lab2.bottle.gif">A soda bottle </a></ul><p>Note that the form a?b:c used in a compute module is a conditional. If a is not equalto zero, then do b, else do c. This allows arbitrary functions to be constructed. Forexample, try r=0.2+(w>=0.4?(w-0.4):0.0) to make a funnel.<p><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/funnel.image.gif"><p>Modify the original Parametric.net program to convert the torus into aspiral spring with four complete turns. Animate the spring so that oneend of the spring remains fixed and the other end undergoes simpleharmonic motion. The spring should not pass through itself and the motionshould repeat every 16 frames. Model a sphere which moves sinusoidally<br>(that is: <code> x(t) = A*sin(w*t+phi) </code>)<br>with the end of the spring and appears to be attached to the spring.One frame of an animation is shown below.<p><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/spring.image.gif"><p><b>Bugs as of 3/7/95 </b><ul><li> The comment in the Construct module is incorrect. It should read"make a 21x21 grid spanning (0,0) to (1,1)".</ul>Be prepared to demo and explain the superquadric function, your sodabottle and spring animation. <p>The<!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/GradeGuides/Lab2.grade.ps"> Lab 2 grading guide </a>will be filled out by a consultant during section to evaluate your work.<p><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/gifs/leftarrow.icon.gif">Back to <!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/index.html">Main Page</a><br><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/gifs/rightarrow.icon.gif">Go to <!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/lab3.html">Lab 3</a> <P><hr>Last modified, 1/17/96, B. Land.<! Revision history: Original document: P.Maxfield, 10/94><br><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><IMG SRC="http://www.tc.cornell.edu/copyright.xbm"><!WA19><!WA19><!WA19><!WA19><!WA19><!WA19><!WA19><!WA19><A HREF="http://www.tc.cornell.edu/ctcCopyright.html"> <i>Copyright Statement </I></A></body> </html>⌨️ 快捷键说明
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