Popular Computing Weekly 08/07/1982 Page 23

Spectrum Programming

In this new slot various contributors explore different aspects of the ZX
Spectrum.

From fans to the third dimension...

Nick Hampshire continues his series on graphics with some standard 3D programs.

Last week I presented two relatively simple programs for rotating a graphic
image on the Spectrum. This first simply moved a single point around the screen
in a circle. This was a development of our attempts to by-pass the Spectrum's
circle command which, as we have discovered, has a number of disadvantages.

The second program was simply a variation of the first program. It rotates a
line stretching out from the centre of the screen around that point.

The first program this week, Figure 1, takes the program a stage further in
trying to create the impression of a rotating fan. I have added the colour just
for effect -- it has no material place in the program. You may, however like to
try changing the colours yourself to make the image more exciting.

Figures 2 and 3 are simply a couple of fairly standard 3D graphics routines
which I have tried on the Spectrum. As you can see, the functions are contained
in line 60 in both programs. it is interesting to try these programs on the
Spectrum simply to give yourself an idea on how fast, or from some points how
slow, the Spectrum is.

As you can see from the two programs, it is quite straightforward to change the
functions in line 60 to create different images.

Just for fun I have thrown in Figure 4 which creates random blocks of colour on
the screen.

As you will have seen on the news pages the Spectrums now going out are being
modified to overcome the clash on the data bus between the ULA and the Z80A CPU
which we reported three weeks ago. We now have one of the first production
batch which has the new modification hand-soldered in. By now the modification
should be built into the production run.

The modification gives priority to the Z80A over the ULA when both are trying
to use the same data. In all other respects the production version of the
Spectrum appears to be the same as the pre-production models which we have, to
date been using for this page.

The only difference which we have noted is that Sinclair, in response to the
criticism in the Popular Computing Weekly review of the machine, in Vol 1 No.
3, has increased the size of the characters on the keys. The red legends are
still difficult to read in poor lighting, but the change is an improvement.
