Sinclair ZX Spectrum

VU-3D from PSION


Load and Run by typing LOAD "vu3d"

VU-3D is a sophisticated three-dimensional design and display program. Using
simple commands, the user may create a solid object or set of objects in three-
dimensional space, observe, modify, print and store such displays. Of course on
a television screen, just like the retina of the eye, only a two-dimensional
representation or image of the three-dimensional world can be portrayed. As
people we get a sense of the three-dimensionality of the world by moving around
and looking at objects from different directions. VU-3D portrays the three-
dimensional world of its data structure, like a software camera, in exactly the
same way as the eve observes the three-dimensional world. And, just like an
individual can walk round an object and look at it from, far and near and from
different directions, so VU-3D includes commands to allow you, the user, to move
round the object and look at it from different distances and directions. In this
way, we can design a solid object and obtain a sense of its reality in the
three-dimensional world.  After loading VU-3D from cassette, the user is asked
if he wishes to create a new design or set of objects. or whether he wishes to
load a data file from cassette. If this is the first time you have used VU-3D,
press the option "1".


CREATE

The CREATE function in VU-3D allows the user, through a Simple set of commands,
to construct a complete new object in 3 dimensions. After entering CREATE a
command banner of 3 lines can be seen at the top of the screen with the data
line at the bottom of the screen. This format is standard and is used throughout
VU-3D. The commands are invoked by pressing the first letter or symbol of each
command.  CREATE functions by taking, in sequence, sections or slices through
the object. Each section, or slice, is called a plane and the different sections
have different Z values. One may think of these Z planes as if one had sliced
through the object with a knife and then examined the surface, so opened. The
points on such a surface now lie in two dimensions which are called X and Y. The
X axis and Y axis are shown along the bottom and the left-hand margin
respectively.  Before invoking CREATE, the user should have some image in his
mind of the object or set of objects he wishes to construct. You should choose
the Z direction to be the axis with the greatest symmetry of the object For
example, a rugby football has an axis symmetry, (the Z direction), along the
line through the two pointed ends of the ball. This line should be chosen as the
Z direction and slices or cuts taken perpendicular to this line. Another example
might be a glass or a cup: the greatest symmetry in these cases is along the
line looking downwards into the cup (Z), and the slices or section (X Y), should
be taken in the horizontal plane across the cup. It is important for the user to
choose Z and the corresponding X-Y planes before he proceeds.  The commands
available to the user in CREATE are: Open, Close, Figure, Magnify, Reduce, Next
Z, Quit and the arrowed cursor keys to shift.

Open

After entering CREATE the user may start an object by using the O for Open
command. This command allows the user to define the shape of the object on the
first plane or section. For example, if a rugby ball was being constructed the
first section. or salami slice, would define a small, regular polygon
approximating a circle.  This polygon is defined in Open. After typing O or
Open, the command banner will change and the user will see a cursor on the
screen. The position of the cursor is given in the data line at the bottom of
the screen. Press the arrow keys to move the cursor around the screen. The first
face of an object is defined bye set of closed lines, closed in the sense that
the line joins up on itself. Position the cursor at the point where you wish to
start the line. Press S for Start. Now move the cursor to the next position to
which you wish to draw a line. Press L for Line and a line will be drawn between
the start position and the present position. Move the cursor to the next point
and press L again.  Continue in this way until you have formed the particular
figure you wish to draw. To close the figure, press E for End. The user will
then be returned to the CREATE function. If, while drawing the lines making up
the figure in Open, an error is made, you may delete the Last line by pressing D
for Delete More than one figure may be included on a section or in the general
display. To start another object, or indeed a hole inside another object, press
O for Open again and draw the second, or more, closed curves under the Open
command.  The lines of a figure may never cross and two figures are never
allowed to intersect. Open will detect any attempt by the user to draw a line
which intersects another line and will not allow such a line to be drawn. If
this occurs, move the cursor until no such intersection occurs. This will also
be the case if the line to complete a figure when the End instruction is invoked
would intersect an existing line.

Figure

In CREATE, either through Open or by repeating a figure from the previous Z
plane, several figures may be included at once. In the commands Magnify, Reduce
and shift with the arrow keys, (below), each of these figures may be magnified,
reduced or moved separately.  This is done by choosing one of the figures in
turn. Press F for Figure to choose the next figure displayed.  The currently
chosen figure is shown with a dotted line as opposed to the solid lines of the
other figures.

Magnify

A figure which has been drawn from Open or repeated by moving to the next Z
plane may be magnified by pressing the key M. Continue to press M until the
figure is magnified to the size you desire.

Reduce

Reduce is the opposite of magnify. Press R to make an existing figure smaller.

Arrows

The cursor arrow keys in the Spectrum may be used to move or shift the figure
left, right up or down.

Next Z

When the figures on the first plane have been constructed satisfactorily, the
user may move to the nest Z plane by pressing the key N until the Z value
required is displayed in the data line at the bottom of the screen. After
pressing N the figures from the previous plane will be repeated on the new
plane. These figures may now be modified using the Magnify, the Reduce and arrow
shift commands. For example, to construct a rugby football, one starts on the
first plane at one pointed end of the football which may be represented by, say,
a regular 10-sided polygon (or with greater accuracy, more sides). This first
polygon is made very small using the Reduce command. N is then pressed for the
next plane and the polygon simply magnified. The neat plane is taken again and
the polygon magnified once more until a plane through the centre of the football
is reached. Further planes are then taken while reducing the figure back to a
small polygon at the other end of the rugby football. The object is then
complete.  An object which is part of the whole scene may be terminated on any Z
plane (apart from the first) using he Close command or another object may be
started on any Z plane by invoking the Open command again.  Holes or hollow
objects may also be devised by using the Open command and drawing one figure
entirely inside another. For example, a mug maybe constructed by drawing a
polygon similar to a circle on the first Z plane, using N to proceed to the next
Z plane, invoking Open again and drawing a smaller polygon inside the first on
the second Z plane. The rim of the mug is then extended by proceeding to a
further Z plane where the object is closed.  Two or more objects may be placed
very close to each other to form a composite object, for example, a cup with a
handle may be devised out of two objects.

Close

To complete a particular object press F until you obtain the figure in question.
Press C for Close to close or complete that object. You may continue to develop
other objects in the scene so long as they are not closed as you move through
further Z planes.

Ouit

Press Q to close any existing objects and to return to the main menu


DISPLAY

Having created an object or set of objects through the CREATE function or having
returned a data file from a cassette, the user may display the object in three-
dimensional perspective through a variety of displays.  There are 3 main types
of three-dimensional representation. These are:  1) a full wire line diagram; 2)
a hidden line diagram; 3) shaded solid diagram. Each of these displays are in
full, three-dimensional perspective.  The user may observe the object from any
position in space, both inside and outside the objects, from any angle and any
distance. To understand the geometry of observing such an object or set of
objects the user may think of himself as sitting on the surface of a sphere with
the object or objects near the centre of the sphere.  The commands of Display
allow the user to move around the surface of this observing sphere and to move
out to larger spheres or move in to smaller spheres.

On entering Display a three-dimensional wire line perspective of the object is
displayed. The orientation and distance of observation of the object should be
chosen by the user through the Near, Far and Arrow commands before asking for a
hidden line or shaded picture, since the latter may use a significant time in
computation.

Far

Press F for zoom away or backwards truer the display and observe the object at a
greater distance. Pressing Caps Shift at the same time as F will move the
observation point back slowly for precision.

Near

Press N to zoom in or observe the object or objects at a closer distance. If you
continue to press N. the observation point may actually move inside the object.

Arrow Keys

Use CSR LEFT to move left, (or change the longitude of observation to the west).
Press CSR RIGHT to move to the right, (or change the longitude of observation to
the east).  Press CSR UP to move upwards or increase the latitude to the north
of the observation point. Press CSR DOWN to move down or increase the latitude
of the observation point to the south. If you press the Caps Shift key at the
same time as arrow keys, the rotation of the observed object will be slowed down
to position the observation point with greater precision.

Magnify

Press M to Magnify the scene. Note that this is different from pressing N for
Near, since the picture in the former case will be magnified but without
increasing the perspective effect.

Reduce

Press R to Reduce the scene. Note that this is different from pressing F for
Far, since the picture in the former case will be reduced but without decreasing
the perspective effect

Quit

Press Q to exit from DISPLAY back to the main menu.


PICTURE

Once you have defined, in DISPLAY, the vantage point or observation point of the
object and its magnification, press P for PICTURE to produce in colours of your
choice a hidden line diagram or solid diagram with shading. The commands under
PICTURE are Shade, Hidden line, Print, Colour, Keep and Quit.

Hidden line

This command produces a hidden tine diagram of the existing picture shown on the
screen. The edges which divide the faces making up the object are shown as lines
but only those edges, which the observer from the present vantage point can see,
are drawn. The edges on the back side of the object are not drawn. The execution
of this command may take a significant time if the display is a complicated one
with many faces.

Shade

Another way of viewing the three-dimensional object or objects is to shade in
those faces of the object which the observer can see.  Those faces which are on
the other side of the object away from the observer are eliminated in this
algorithm.
The lightness of the shading of each face is determined by a combination of a
diffuse background light and by "diffuse reflection" from a single light source.
After pressing S for Shade the command panel at the top will change and ask the
user where he wishes to place the light source. In answer to the first question
enter a,c or b for the light to be above, from the centre or below. In answer to
the second question enter l, c or r to position the light source at the left,
centre or right respectively.

Colour

The background colour and the colour of the objects in the display may be chosen
with the Colour command.  Press keys 0 to 7 to choose the appropriate colour in
each case according to the questions in the command panel.

Print

Press key P, if a printer is attached to the Spectrum, for a hard copy record of
the display.

Keep

Allows you to keep a record of the display only on cassette. Note that Keep
differs from Save in the main menu since Save stores on tape the complete data-
file of the object on cassette. Keep, on the other hand, simply saves the screen
image and can he loaded later from cassette using SCREEN$ without the VU-3D
software. On pressing K for Keep you will be asked for a file name and
thereafter told to connect the tape recorder to the Spectrum and to start the
recorder on record.

Quit
Q returns the user to the display function.


MODIFY

After an object or set of objects have been defined through the CREATE function,
the user may later wish to change or alter the objects. This may be done through
the MOD1FY function providing the changes to be made are not of a major kind. If
the new figures are to be substantially different from the existing figures, the
user should rather ABANDON the file and CREATE a new set of objects.
The MODIFY function works in a very similar way to the CREATE function and will
take the user through the sequence of sections or Z planes previously defined
through CREATE. On entering MODIFY the display will change to show the existing
two-dimensional figure drawn on the Z = 0 plane. The commands then available to
the user are Magnify, Reduce, CSR LEFT, CSR RIGHT, CSR UP, CSR DOWN, Next Z and
Quit. These commands are precisely the same as those in CREATE.


ABANDON

This function deletes or abandons an existing data-file to leave memory for a
new data-file formed from CREATE or LOAD.


SAVE

The Save function is called from the main menu of VU-3D. It allows a user to
save permanently on cassette a data-file which has been created. Connect the
microphone socket on the Spectrum to the microphone socket on your tape
recorder, define a file name and press the record button on your recorder.


LOAD

This function allows the user to retrieve from cassette a previously defined VU-
3D data-file. To load such a data file there must be no existing data-file in
the memory of the Spectrum. If there is such a data-file use the ABANDON
function first before entering LOAD.


SIDE B: EXAMPLE

Load and run by entering LOAD "example".



Copyright Psion Ltd. 1982.  No part of this recording shall be reproduced
without written permission. While every precaution has been taken in the
preparation of this recording, the publisher assumes no responsibility for
errors nor liability for damage arising from its use.

Made in U.K.