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Date: Mon, 16 Dec 1996 22:10:29 GMTServer: NCSA/1.5Content-type: text/htmlLast-modified: Mon, 26 Feb 1996 14:39:35 GMTContent-length: 5247<html><head><title>CS418 Lab 7</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 7</h2> <h2> Image Techniques </h2><p><b> Introduction. </b><p>In this exercise you will treat images as data to performvarious useful graphics operations including texture-mapping, volumetexture-mapping, and bump-mapping. <b><hr>Procedure:</b><p>First you need to download several example files. To do this, click on each of the filenames shownbelow. When the text window opens, use the "save as" option to put the file in your own directory. Nameeach file with the same name as shown below. <p><ul><li> <!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><!WA1><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/imageRead1994.net"> imageRead.net</a><li> <!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><!WA2><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/imageRead1994.cfg"> imageRead.cfg</a><p><li> <!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><!WA3><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/Image2Texmap.net"> Image2Texmap.net</a><li> <!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><!WA4><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/Image2Texmap.cfg"> Image2Texmap.cfg</a><p><li> <!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><!WA5><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/Volume1994.net"> Volume.net</a><li> <!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><!WA6><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/Volume1994.cfg"> Volume.cfg</a><p><li> <!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><!WA7><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/bumpmap.net"> Bump.net</a><li> <!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><!WA8><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/bumpmap.cfg"> Bump.cfg</a><p></ul><b> Texture Mapping:</b> The programimageRead.net will show you how to read an image, display it,and find its size. Note that an image in DX has a physical sizecorresponding to its initial resolution in world units, e.g. a 100x200resolution image is 100 by 200 world units in size in the x-y plane withone corner at the origin. The reduce module lowers the resolution but doesnot change the size of the image, as you can see from the output of theStatistics modules which are configured to determine the max and min of thex,y coordinates of the image. Vary the interactor to change the imageresolution. An image consists of a 2D field of 3-vectors representing thered, green, and blue values at each point. Marking the component "colors"of an image allows manipulation of the image. <p>The program Image2Texmap.net creats a flag image, then animates it as a texture-mapped, parametrically distorted plane.<p><b>Volume Texture Mapping:</b>A volume texture map (see page 246 of <i>Watt</i>) produces a surface coloron an object which is a function of the 3D coordinates of the surface. The program Volume.net gives an example of two volume textures; stripes andnoise (see <!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><!WA9><a href="#IM3a">Images 3a+b</a>). <p><b> Bump Mapping:</b>Bump-mapping attempts to give a surface more interesting texture byvarying the normals to the surface. The procedure causes the lightingmodel to assign different colors to patches of a surface, making it appear rougher. Two bump maps are shown below, a random perturbationof the normals and one that resembles tiles. <p><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><!WA10><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/lab7.bump.random.gif"><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><!WA11><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/lab7.bump.tile.gif"><p><b> <hr> Assignment:</b><p>Construct a scene which includes:<ul><li> A flag of your own design, waving in the wind.<li> An image from the <code>/afs/theory/tc/courses/418/TexMaps</code> directoryas a backdrop.<li> A hemispherical mirror which reflects an image of the flag.This is a wide-angle image rendered from a viewpoint behind the flag, thenparametrically deformed into a hemisphere.</ul><p>The following image is one possibility. A flag is reflected in a mirrorwhich is placed behind and below the flag. The sky is an image which has been parametrically warped into a cylinder.The image on the right shows a view of the scene zoomed out to show the"sky".<p><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><!WA12><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/lab7.mirror.image.gif"><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><!WA13><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/lab7.mirror.zoom.image.gif"><hr>Design functions to produce volume textures simulating:<ol><li> a wood grain of concentric growth rings<li> marble <li> fiberglass </ol>The new textures should be incorporated into the existing selector list on the control panel.In addition, modify the program to map the textures to a sphere andadd an interactor to select between the sphere and the planes.The volume textures supplied in the program are shown below.<h4><a name="IM3a"><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><!WA14><img align=bottom src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/Volume1994.1.gif"> </a><a name="IM3b"><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><!WA15><img align=bottom src="http://www.tc.cornell.edu/Visualization/Education/cs418/labs/labgifs/Volume1994.2.gif"> </a></h4><hr>Starting with the program Bump.net, design bump maps which resemble:<ul><li> Snow covered ground.<li> A corn field.<li> Bricks with mortar.</ul><hr>Be prepared to demo:<ul><li> Your waving flag reflected in a hemispherical lens.<li> The three volume textures.<li> The three bump maps.</ul> <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><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><!WA16><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/gifs/leftarrow.icon.gif">Back to <!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><!WA17><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/index.html">Main Page</a><br><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><!WA18><img src="http://www.tc.cornell.edu/Visualization/Education/cs418/gifs/rightarrow.icon.gif">Go to <!WA19><!WA19><!WA19><!WA19><!WA19><!WA19><!WA19><!WA19><a href="http://www.tc.cornell.edu/Visualization/Education/cs418/lab8.html">Lab 8</a> <P><hr>Last modified, 1/18/96, B.Land.<! Revision history: Original document: P.Maxfield, 10/94><br><!WA20><!WA20><!WA20><!WA20><!WA20><!WA20><!WA20><!WA20><IMG SRC="http://www.tc.cornell.edu/copyright.xbm"><!WA21><!WA21><!WA21><!WA21><!WA21><!WA21><!WA21><!WA21><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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