Getting to grips with graphics and sound
BBC Micro Graphics and Sound aims to explain the graphics and
sound facilities of the BBC Micro in simple terms and to show
how they can be used.
Each of the micro's graphics and sound statements are explained,
usually in a more readable form than in the User Guide.
To demonstrate the ideas and techniques discussed there are
more than 80 program listings and examples.
The book explains the techniques and equations necessary to
draw two dimensional shapes, such as polygons and circles, and
shows how to rotate them.
Several methods of achieving the same result are given with
an indication of the best one for a given situation.
Also a section on three dimensional plotting, including perspective
and rotation, shows how realistic displays can be produced.
The chapters on colour help to clarify, the use of the various
plot and fill commands and shows how the GCOL statement works.
Using this information, clever methods of erasing lines and
simple ways of hiding objects behind other objects are shown.
Methods of using colour and graphics in Mode 7 are also discussed.
The mathematics involved in some of the explanations is difficult
to follow, particularly in the three dimensional section, but
this is partly due to the nature of the subject matter.
The examples, however, do enable you to use the techniques illustrated
without necessarily understanding the mathematics.
A very useful section on graphs and charts shows how bar and
pie charts in two or three dimensions are created.
The section on the BBC Micro's sound facility helps to simplify
the complex ENVELOPE command. It shows with numerous examples,
how to make the sounds you want.
Despite this I get the impression that the author is unfamiliar
with the BBC Micro, as he has made many mistakes about BBC Basic.
For instance, he failed to acknowledge the existence of the
keywords RAD and DEG, and suggested that to change degrees to
radians use the formula RAD = DEG * PI / 180.
Similarly, he interpreted the statement GCOL4,C to mean that
the colour plotted would be the inverse of the colour C. It is,
in fact, the inverse of the colour already on the screen.
There are also errors due to misprints. Happily all these are
usually easy to detect by running the book's examples and suggestions
on the computer.
Also one understands something far better if you've had to find
the mistakes first.
Having said this, the book is a useful reference for people
wanting to know how to draw graphs, shapes, and patterns, and
handle three dimensions, animation and the envelope commands on
their BBC Micro.
Eric H. Crisp
