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Date: Mon, 16 Dec 1996 22:11:15 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Wed, 06 Mar 1996 18:11:51 GMTContent-length: 4855<html><head><title>CS418 Lab 4</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 4</h2> <h2> Using a virtual camera </h2><b> Introduction. </b><br><p>This exercise introduces the concept of a "virtual camera". The virtual camerais a set of transforms which takes a 3D representation of a set of objectsand arranges for them to be shown in a 2D window.By analogy, a 35mm film camera transforms the 3D world into a fixed size (35mm) image, viewed from a certain point, with a certain focal length of lens. Fora virtual camera we will need to specify where the camera is, where it ispointed, the width of the field of the camera, and perhaps other parameterswhich a real camera cannot have (e.g. clip planes, or variable aspect ratio).<b><hr>Procedure:</b><p>First you need to download several example 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/cameraIntro.net"> CameraIntro.net </a><li> <!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/cameraIntro.cfg"> CameraIntro.cfg </a><p><li> <!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/cameraINscene.net"> cameraINscene.net </a><li> <!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/cameraINscene.cfg"> cameraINscene.cfg </a></ul><p>Open the program CameraIntro.net and its control panel. When you execute it youwill see that two image windows are opened. One is controlled by the familiarImage module. The other is controlled by a Camera and Display module. TheCamera module gives you explicit control of the viewing parameters. Whereas theimage module always points at the scene (by default), an explicit Cameracan point anywhere you want and can be controlled by the program itself. On thecontrol panel, switch the selectors to the Animate position and run thesequencer. The position of the Camera (the "from" parameter) and the up directionare now a function of time. The contents of the two compute modules which control the camera are shown<!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/cameraIntro.net.gif"> here. </a><p><b> Bugs found as of 2/23/96 </b><p><ul><li> In the "program fragment" hyperlink replace "approxUP" with"norm(approxUP)" in the second compute module expression.</ul><b> <hr> Assignment:</b><p>Model a TV sitting on a table next to a simple still life. Model a TV camerafloating in space (chassis, lens tube, lens). Define <!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/TV.controls.gif"> interactors </a>to controlthe position, look-to point, up direction, and zoom angle of the TV camera.Use these interactors to orient the TV camera in space and to control a Camera module to produce the image the TV camera would see. Put the imageon the front of the modeled TV as shown in the image below.(The cameraINscene program "mirror" is very similar to the TV set.)You will need to convert the control interactors into rotations and translationsof the TV camera. The Transform module allows you to rotate by an arbitraryset of basis vectors.A <!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/TV.net.camerafrag.gif"> program fragment </a>helps to explain how to take the three input vectors (to, from, up) and convert them to a camera rotation matrix.Your program does not need to show the recursive image if the camera happensto be looking at the TV screen. (See image below, right.)It is more important to be able to control the camera in space and showthe resulting image than to make a fancy TV set or camera model.<p><!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/TV.image.gif"><!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/TV.image.nopict.gif"><p><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/student.1995.gifs/lab4.95results.html"> Some results from 1995. </a><p><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/student.1996.gifs/lab4.96results.html"> Some results from 1996. </a><p>Be prepared to demo your TV program during section for a maximum of 15minutes. You will be graded on the correctness of the camera control and thereadability of the program.<p><b>You must document your code!</b> Layout small groups of modules which fit onone screen and connect them to other groups with transmitters. You shoulduse transmitters/receivers, macros, and comments in the "Notation" field ofeach module so that you and the grader can understand the program. Controlpanels, if any, should be well organized, labeled, and with the appropriatenumeric ranges.<p>The<!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/GradeGuides/Lab4.grade.ps"> Lab 4 grading guide </a>will be filled out by a consultant during section to evaluate your work.<p><p><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/gifs/leftarrow.icon.gif">Back to <!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/index.html">Main Page</a><br><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/gifs/rightarrow.icon.gif">Go to <!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/lab5.html">Lab 5</a> <P><hr>Last modified, 2/23/96, B. Land.<! Revision history: Original document: P.Maxfield, 10/94><br><!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><IMG SRC="http://www.tc.cornell.edu/copyright.xbm"><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><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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