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Using AVS/Express in an Introductory Computer Graphics Course

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2 Course Structure Undergraduate course is a modular scheme Students study 8 modules per year, each one for 15 weeks, for 3 years Second year: Tools for Graphics and Visua lisation Third year: Methods for Graphics and Visualisation

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3 Tools for Graphics and Visualisation Uses 2D images to implement some of the standard algorithms in computer graphics:- –draw a circle –rotate, scale, and translate a 2D shape –window to viewport transformation –calculate co-ordinates of intersection of 2 lines –zoom in and out, & pan up/down/left/right –Bezier Curve drawing to fit 4 points

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4 Visualisation component Create 3D shape from either: - –2D profile –surface co-ordinates Use AVS/Express to visualise the 3D shape Use AVS/Express to animate the 3D shape

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5 Draw a Circle The co-ordinates of any point on the edge of a circle centred at the origin may be obtained from the following equations: - X = Radius*cosine( ) Y = Radius*sine( ) where is the angle in radians between the X axis and a point on the circle (in an anti-clockwise direction)

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6 Draw a Circle =degrees* /180 X = Radius*cosine( ) Y = Radius*sine( ) X-axis Y-axis Radius

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7 Create 3D solid from 2D profile Profile Y X Solid of revolution of bottle shape Y X Z

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8 Create 3d solid from 2D profile The students use the circle code to generate the X and Z co-ordinates (the Y co-ordinates remain constant for each point on the profile) They also have to generate an extra set of co-ordinates (exactly the same as the first set) to make AVS/Express join the last point up to the first one.

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9 Surface Plot Specify a regular grid for the (x,y,z) co-ordinates Student has to generate a height for each co- ordinate based on a random number

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10 a b c 3D Surface Randomly modify its new height within limits Create a new mid-way point Make its height the average of the adjacent points

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11 Include the diagonals Also along the diagonals based on the heights of the four corners (a, b, c, and d) a b d c

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13 Field file for a bottle # AVS field file # bottle ndim = 2 dim1 = 21 dim2 = 15 nspace = 3 veclen = 1 data = integer field = irregular

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14 Field file for bottle (continued) coord 1 file=bottle.dat filetype=ascii skip=0 offset=0 stride=4 coord 2 file=bottle.dat filetype=ascii skip=0 offset=1 stride=4 coord 3 file=bottle.dat filetype=ascii skip=0 offset=2 stride=4 variable 1 file=bottle.dat filetype=ascii skip=0 offset=3 stride=4

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16 3D axis with text title Bottle

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17 Used crop to reduce the number of horizontal steps drawn Crop

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18 Used crop to reduce the number of vertical points drawn Crop

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19 Used downsize to reduce the number of steps drawn around the circle Downsize

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20 Used downsize to reduce the number of profile points drawn Downsize

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22 Field file for 3D solid example # AVS field file ndim = 2 dim1 = 9 dim2 = 11 nspace = 3 veclen = 1 data = integer field = irregular

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23 Field file (continued) coord 1 file=xmastree.dat filetype= ascii Skip=0 offset=0 stride=4 coord 2 file=xmastree.dat filetype= ascii Skip=0 offset=1 stride=4 coord 3 file=xmastree.dat filetype= ascii Skip=0 offset=2 stride=4 variable 1 file=xmastree.dat filetype=ascii Skip=0 offset=3 stride=4

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25 Neither downsize nor crop used on the first image

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26 Used downsize to reduce the number of steps in each circle Downsize

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27 Used downsize to reduce the number of profile points Downsize

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28 Used crop to reduce the number of horizontal steps drawn Crop

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29 Here is a selection of some other shapes created by the students

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30 “Brolly”

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31 “Rings”

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32 “Speaker”

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33 Cross section of a “speaker”

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34 Two stroke cylinder

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35 Animation using AVS/Express Once an image has been created, the students can animate the image using the keyframe method of animation This creates a series of views (keyframes) AVS/Express can save images from a view Then add frames between the keyframes to produce the animated sequence

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36 Key-frame animation Need two images which depict the start and end frames Create an animation sequence by adding frames between the two images The two images must have a reasonable level of coherence

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37 AVS/Express AVS/Express interpolates images between a series of captured visualisations Student captures the keyframes Assigns each keyframe to a time step AVS/Express automatically adds the required number of frames between these keyframes to produce an animated sequence

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38 Keyframes and interpolated frames keyframes the user defines interpolated frames added by AVS/Express

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39 AVS animation features Simple to add/delete/move keyframes If not a regular time interval between keyframes, then specify the time of next frame before adding it Can create a cyclic animation Playback control offers forwards, backwards, and “bounce”

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41 Keyframe Controls

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42 Module Panel Modules pull-down menu Playback the animation

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43 Finally... Create 2D profile Create 3D data Use AVS/Express to animate the image Use AVS/Express to visualise the data This is how we teach visualisation in a level 2 module: - What could we do in the level 3 module?

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