The 3-D Animator

By Philip Robinson


Issue 30

Nov/Dec 87

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In Issue 26 Philip Robinson presented Solid Modelling which allowed you to create complex objects with shading to give a three dimensional effect. Now he goes further with a super program that not only allows you to create true 3-D objects but also allows you to animate them at high speed!

Have you ever wanted to sit in front of your computer, sketch a simple outline of an object with a joystick and then watch as your computer turns the outline into a full 3-D image complete with hidden surfaces? The 3-D Animator will do this for you but it will also allow you to view the 3-D image at any orientation and scale with a variety of surface textures and it will automatically calculate and record different views of the image and play them back at high speed to produce full 3-D animation!

Sounds interesting? Type in the listings, following the instructions given carefully, and you will then be ready to follow the Tutorial which will teach you how to use The 3-D Animator fully. After that, use your imagination to create and animate some beautiful objects of your own.

The 3-D Animator will only run on 48k disk based / systems and uses virtually all of the available memory. In order to leave as much memory as possible available for images, the individual modules are only loaded when required and there is minimal error trapping, so take care, especially when entering filenames. Note that even small changes to the listings may cause the program to crash.


The easiest way to learn how to use The 3-D Animator is to follow a tutorial, so boot up your 3-D Animator disk and follow each of these steps which will start with drawing a simple image and end up with a fully animated Image File. Before beginning, take note that your 3-D Animator disk must be left in the drive at all times and must not be write-protected. Note also that error trapping in the program is minimal and it is particularly important to include the drive specifier (D:) in all filenames.


Let's begin by creating a simple image. Select Option 1 – Generate an Image from the main menu and the Graphic Editor screen will appear. A joystick plugged into port 1 will control a small single pixel cursor which can be positioned anywhere on the right hand side of the screen. The space bar will toggle between a fast or slow cursor. Try it.

Our first shape will be a square headed nail as shown in Figure 1. This shows the Graphic Editor screen with an outline drawn on it and a view of the 3-D image that will be generated from the outline shown. Position the cursor at point A and press the fire button (a short sharp press to avoid, selecting the point twice). Move the cursor to point B, press the fire button to select the point, and then move to points C and D pressing the fire button each time. Now press any key on the keyboard and you will be prompted for the 'Number of sections' required.

This represents the number of 'steps' taken in rotating the outline around the central axis when forming the 3-D image. In this case a square headed nail is required so enter 4 in response to the prompt and press Return. A prompt for the filename will now appear. Enter the drive and a filename in the normal way but do not specify any extender. Note you must include the drive specifier. For our tutorial use the filename D:NAIL.

Four files will now be created. Using the example given these will be NAIL, NAIL.XYZ, NAIL.FAC and NAIL.CTL. You will see messages as each section is processed and information is stored into two of the files (NAIL.XYZ and NAIL.FAC). When all the sections have been processed a message will appear showing the number of coordinates required to represent the 3-D image. The number of coordinates is calculated as follows:

(Number of points) x (numbers of sections + 1)

The 3-D Animator can only display images with up to 98 coordinates due to memory limitations so you must not exceed this limit or the display function will crash! With our square headed nail, the number of coordinates message should be 20 –(4 points) x (4+1 sections) = 20.

Following this message will be a prompt asking if more outlines are to be added to the image. Enter Y and then add points E, F, G from Figure 1 in that order. Next press any key on the keyboard and the prompt for 'Number of sections' will appear again. This time we require a more rounded shape for the shaft of the nail so enter 6.

Each section will now be processed and messages will be displayed as further information is stored into the two files NAIL.XYZ and NAIL.FAC. The number of coordinates message which appears after processing is complete should now be 41:

A,B,C,D (4 points) x (4+ 1 sections) = 20

E,F,G (3 points) x (6 +1 sections) = 21

Total = 41

Now enter N to the prompt asking if more outlines are to be added to the image and a message 'Completing image file' will appear. Information will be stored in the NAIL.CTL file and you will be returned to the main menu.

At this stage details of the 3-D image are stored in the three files NAIL.XYZ, NAIL.FAC and NAIL.CTL. These three files are collectively called the Image File. The fourth file (NAIL) is empty, ready to be used for storage of views of the 3-D image.

TWO SIMPLE RULES: When drawing outlines you must conform to two simple rules:

1. Outlines must be drawn in a clockwise direction. In the NAIL example you did that by drawing the points in the order A,B,C,D for the first outline and E,F,G for the second outline.

2. Outlines must be 'closed'. They can be closed either by the central axis being part of the outline or, if drawn away from the central axis, by closing the outline itself (i.e. a square, triangle etc.) The outlines for the NAIL are closed by the central axis along the lines AD and DG.


Now you have drawn an image in outline which has automatically been saved to disk, it is time to have a look at what the 3-D image looks like. Select Option 2 – Display/File Views of an Image from the main menu. A prompt will appear asking for the name of an Image File. This can be any image that you have created and which is on your 3-D Animator disk. Remember to enter the drive specifier followed by the filename of your image but do not specify an extender.. In this tutorial example you enter D:NAIL. The image will be read from the NAIL.XYZ, NAIL.FAC and NAIL.CTL files into memory and the screen will blank.

The following control keys are now active.

D – Display/File views of an image
V – Viewing specifications for an image
I – Initialise (to null) settings for rotation, scaling and transformation of image
R – Specify rotation of image
S – Specify scaling of image
T – Specify transformation of image
E – End (Return to main menu)

The first thing to do is see what our image looks like so press the D key and you will see a prompt for the 'number of displays' required. For the time being we only want to see the image on screen so enter 1 and you will then be asked if you want 'filing'. Enter N and press Return. If you enter Y the resulting image will be saved to disk and will overwrite any existing image.

The 3-D Animator will now start generating the display. There are many calculations involved so the screen is 'turned off' allowing more CPU power to be devoted to the calculations. So that you will know that the computer is still working, it will 'beep' once after each of the three major sets of calculations it performs and after the third 'beep' the display will be turned on and the image will be drawn. A fourth 'beep' will indicate when the image is complete.

Selecting a Different View

You should now have a front view of your nail but this doesn't show the 3-D nature of the image very well so we will rotate it into a better viewing position. Press the I key which will initialise all the rotation, scale and transformation settings to null. A message will be briefly displayed indicating that the settings are initialised. Press the R key and you will be prompted to enter the rotation (in degrees) that you require for each axis. Positive values will rotate the image in the directions shown in Figure 2, negative values in the reverse directions. Enter 45,0,45 to rotate the image around both the X and Z axes and wait for the prompt to disappear.

Each time you change the image you must redraw by pressing the D key. You will know when the image is ready because any on screen prompt will disappear, so wait and then press D. Request 1 display and no filing and after the calculations ',blank screen, three 'beeps'), the image will be drawn. If you watch the image you will notice how it is built by drawing the most distant parts first with the nearer parts being overlaid on top. This is the so-called 'Painters Algorithm' and provides the correct display of the image with regard to 'hidden surfaces'. You now have the image of the nail viewed from a different angle.

Scaling and Moving the Image

Supposing you want to enlarge or reduce the image? No problem, just press the S key and you will be prompted to enter the scaling factor that you require for each axis. You may scale each of the three axes independently allowing you to make, for instance a 'fatter' or 'longer' image. Enter 0.6,0.6,0.6 to reduce the size of each axis to 6 tenths of its original size and wait for the prompt to disappear. Press the D key, request 1 display and no filing and the reduced image will be drawn. You will see that the image has reduced in size but it has also rotated. Why?

An important point to remember regarding rotation, scaling and transformation is that each change is 'added' to any previous change unless the settings are initialised first. If only scaling had been required, the I key should have been pressed prior to setting the scaling factors.

Now, let's put the image back to its original size. Press the I key followed by the S key and enter 1.67,1.67,1.67 to scale the image up to its original size. Press the D key, request 1 display and no filing and as the image is drawn you will notice that it doesn't rotate this time.

So far we have changed the viewing angle of the image and reduced and enlarged it, but suppose we want it move to another part of the screen? This is where 'transformation' comes in. The T key works in a similar way to the examples given so far but moves the image along its axes with the values entered representing the distance moved in pixels. Positive values cause movement in the directions shown in Figure 2 and negative values will move in the reverse direction. A WARNING! No 'clipping' of the image is performed and the program may crash if the image overflows the screen boundaries of Graphics 8 i.e. 320(X) by 192(Y). This option has been omitted in the interests of speed and to allow maximum use of memory for images. If you do crash, you may start again by entering RUN "D:MENU.3D". When the main menu appears you must start right at the beginning with Option 1 – Generate an Image, however if you hadn't filed any views of images before the crash you can start at Option 2 –Display/File Views of an Image. With a little care you can easily avoid this problem anyway.

Adding Texture

Having got this far you should be able to draw any image and manipulate it on screen as you wish, so let's take a look at one final option before finding out how we can animate the object we have created.

The images displayed so far have been white with black edges (the initial default) but many more options are available. Press the V key and you will be prompted for a shade value. This value determines the density of pixels that are set on the surfaces of an image. The value can range from 0 for all pixels on (white) to 64 for no pixels (black). Enter a shade value of 60 (almost black) and you will be prompted for the texture of the surfaces. A response of Y will give a regular effect known as a Half-Tone and a response of N will give Random effect. Enter Y for Half-Tone. You will now be prompted for white or black edges. Enter Y for white edges. The image will now be drawn again (no rotation, scaling or transformation is performed) using the new specifications.

Try some of your own settings to see the effects. For a `wire-frame' image enter 64 for Shade, Y for Half-Tone and Y for White Edges. To return to the default settings enter 0 for Shade, Y for Half-Tone and N for White Edges.


You should now be able to display an image at any orientation, scale and texture so now comes the big moment! Let's produce a moving image.

Firstly you should position the image using the features you have learned so far, so that it looks roughly as in Figure 1. You should have white surfaces and black edges. If you can't manage to get back to that view, don't worry, it is not that important so long as you have a good view of the image otherwise the animation could be disappointing.

Animation consists of rotating the image through a number of steps. Press the I key to initialise all rotation, scaling and transformation and then press the R key. Enter 0,90,0 to rotate the image around the Y axis and then press the D key and request 5 displays with filing.

The next process will be automatic and in this example will take around five minutes. Five displays will be generated and filed on disk (in the NAIL file) and after filing each display, a message will briefly appear showing the total amount of data written to disk so far and the number of displays still remaining to be generated and filed. Keep an eye on the amount of data written for each image as it will show you how many displays you can have in the Image File if you should want to change it later.

When all displays have been filed the image will remain on screen but the 'Filing – Please wait' message will disappear. The process is virtually complete so press the E key and after a little more file activity you will be returned to the main menu. You can now use Option 3 to view your animated sequence. Simply enter D:NAIL when prompted for a filename.

That's just about it, except for one final option when you are viewing an animated sequence. Pressing any key apart from F will abort the image and return you to the menu but the F key allows you to select the speed of the animation. The speed is initially set to the maximum of 256 (approximately 1 tenth of a second) which is the slowest animation. Try a delay of 100, or less, for some really fast moving shapes!

TWO SIMPLE RULES FOR ANIMATION: When producing animated sequences you must conform to these two simple rules.

1. The first and last display in the animated sequence must be the same. In the NAIL example you did that by rotating the image through 90 degrees five times – think about it!

2. The animated sequence file must not contain more than 22,000 characters of data due to memory limitations, which is why it is important to note the amount of data written for each image. When producing an animation, it is wise to generate and file a few displays to start with so that you can judge the likely size of the final file by watching the data written messages. Obviously simple shapes can be animated through more stages than more complex ones.

There you have it! You should be able to create some superb objects and animate them as you wish. Use your imagination to combine as many of the features as you can and have fun! I hope that you have as much enjoyment using The 3-D Animator as I did in developing it!


The program is split into seven listings and all of these must be on the same disk. Any image files created must also be on this disk so it is recommended that you start with a newly formatted disk before typing in the listings. Now follow these instructions carefully.

1. Type in each of the listings separately, checking them with TYPO 3 as you go, and SAVE each to disk. Note that you should type NEW after each listing has been SAVEd. The listings MUST be saved with the following filenames.

Listing 1 should be D:LOADER.3D
Listing 2 should be D:ANIMATE.3D
Listing 3 should be D:ASM.3D
Listing 4 should be D:MENU.3D
Listing 5 should be D:GEN.3D
Listing 6 should be D:DSP.3D
Listing 7 should be D:PRJ.3D

If you don't use the above filenames the program will not work.

2. With the disk containing the above files in drive 1, type RUN "D:LOADER.3D". This will create three additional files on the disk, OBJ1.3D, OBJ2.3D and OBJ3.3D.

3. The file LOADER.3D is no longer required and can, optionally, be deleted from your disk (make sure you have a copy on another disk, just in case!)

4. Note that the main disk MUST be used for storing all Image Files created with the program so it is recommended at this stage that you make a working copy using the DOS duplicate disk function. Write protect your original and file it away and use the working copy which should not be write protected.


1. Boot up the computer using DOS 2 or 2.5, insert your 3-D Animator disk and type RUN "D:ANIMATE.3D". The program will load the various routines and present you with the main menu.

2. If you have any problems you must switch off before running ANIMATE.3D again.

Listing 1 outputs are on issue disk

Listing 2

AtariLister - requires Java

Listing 3

AtariLister - requires Java

Listing 4

AtariLister - requires Java

Listing 5

AtariLister - requires Java

Listing 6

AtariLister - requires Java

Listing 7

AtariLister - requires Java