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MAN_34
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Creating a 3D Object #2
Before starting this tutorial
itself, it is vital to explain the
principles and basic ideas which govern
the use of the 3D system offered by
Canvas. Firstly, it is important to
recognize that the objects are made up
of individual lines, which, when
separate, have no solid form, but when
placed in a formation create a 3
dimensional image.
Solid objects cannot be created.
The only way of creating these is to
plot an object (wire frame) and draw in
the edges (using the user-defined
polygon mode for instance) - also see
tutorial #3.
The object editor is known as the
3D Construction Studio and is capable
of storing 8 objects at once, each
containing up to 256 separate lines.
This number of lines should be easily
adequate for any object you want. Each
of these lines consists of 2 points
(the Start and End, of course). The
editor is based on a 1st angle
orthographic projection. Sounds
gruesome eh? It simply means that you
edit the lines on 3 planes (x,y and z)
using an Above, End and Side view.
Creating a 3D Cube
We'll take a cuboid shape to use in
this example. Consider the shape of a
cube - it has 12 edges so we will need
12 lines eventually. It also consists
of 6 faces. Since the 3D editor is not
POLYGON-BASED, we must ignore the sides
themselves and just think of the cube
as a formation of 12 lines.
1) Fortunately, the editor offers
the possibility of setting up a
formation of lines which form a
polygon. Set the Poly Sides Infobar to
4 (each side has 4 lines). Now press
the Add Poly button and select a
square(ish) shape - it will appear more
like a diamond, but never mind!
2) Select Y as the Axis and use the
<Shift< button to shift the shape up on
the Y Axis until the height (Y) of it
(look at the co-ords at the bottom) is
the same as the biggest Z value.
3) Now go onto another object (use
the 1 to 8 selector). If there are
already lines in it, use the Clear Obj
button to erase them. Now Select the
object number of the object where you
drew the diamond, on the Add Obj
Infobar and then click the Add Obj
button. Click Yes on the Alert box. The
diamond should appear on the current
edit windows.
4) Use >Shift> to shift the diamond
on the Y Axis again, but the other way,
so that it is opposite the centre from
where it was before.
5) Again click the Add Obj button
without changing the Infobar value. You
should now have two diamonds at
different heights and a total of 8
lines in existance.
6) Keep increasing the number in
the Line Infobar until you find a line
which does not exist (a cross at the
bottom right of the screen means that
it doesn't exist and a tick means that
it does). The value should be 8.
7) Click on the Add Line button to
bring Line 8 into existance. A dot will
appear in the centre of the edit
windows. Note that both ends of the
line are at 0,0,0 0,0,0. Click on the
edit windows to move the ends of the
lines. To change which end of the line
you edit, use the S/E (Start/End)
Selector in the bottom left. You will
find it very difficult to position the
ends of the lines in the right places.
To help you, you must switch on the Fix
button. Now, if you click on the Edit
windows, the point will be placed at
the nearest point already in existance
to the place where you clicked (think
about it!). So, if you click near one
of the corners of a diamond, that point
will be placed at that corner - no
messing around trying to be
mega-accurate!
8) Create another 3 lines and place
them vertically between the 4
corresponding vertical pairs of point
on the 2 diamonds.
9) Now check that there are 12
lines in existance (see value in bottom
right), and that the object in the edit
windows looks about right - it may be a
little hard to visualize, but there
should not be any diagonal lines except
for 4 on the Above view. If there are,
something has been done wrong. Go
through the lines using the Line
Infobar until the suspect line appears
in a different colour to the rest -
lo-res only. Change the line's position
so that it is correct.
10) Now that you have the cube,
click on the View Obj button to enter
the Viewing Studio. You will see in the
centre of the viewing window the cube.
Rotate and move it about until you are
happy about it and then press Plot to
place it onto the current work screen.
Phew!! That was quite a 'tuffie' to
explain! If you can't visualize an
object on the edit windows then load in
the "EXAMPLE.3D" file (in the "_THREE_D"
folder) and look through the objects in
that.