Using AVS/Express in an Introductory Computer Graphics Course

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

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

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

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)

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

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

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.

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

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

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

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

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

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

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

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

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

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

27 Used downsize to reduce the number of profile points Downsize

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

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

30 “Brolly”

31 “Rings”

32 “Speaker”

33 Cross section of a “speaker”

34 Two stroke cylinder

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

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

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

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

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

42 Module Panel Modules pull-down menu Playback the animation

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?