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Retained
Mode: Putting it all together
By: Jack Hoxley
Written: June 2000
Download:
RM_Complete.Zip
(103kb)
There is one inherant problem
with reading lots of tutorials - you can learn every aspect of a subject, yet
still not be able to create a proper program. This feature is less of a tutorial
and more of a guide. In it I will show you how to use your retained mode knowledge
to create a simple program.
The program in particular will
be a logo program. The idea behind it is to create a titlescreen type effect
that stands out from the crowd. It will use the following features:
- Enumeration - to select hardware
or software
- Loading in a primative to
hold our logo
- Loading and using a texture
as our logo
- Using rotation and movement
to modify our primative
- Using dramatic lighting to
enhance the graphics of our logo screen.
Why use retained mode for this?
Retained mode is simple; this project will take half as much time to create
than if I had written it for immediate mode. As well as this, retained mode
isn't really appropriate for games (the other possible project) any more - If
I were to write a game it would be in immediate mode.
The first part that the user
sees is an options dialog; this is quite common in games, it allows the user
to select various options to suit their computer setup. Mine looks like this:
This is a screen
shot from my Pentium 166, which only supports software rendering; normally Hardware
would also appear in the combo box; and be the default selection. Then there
is detail settings. This is nothing to do with code; when I built the objects
in 3D Studio Max I made two identical versions; one with a high poygon count;
the other with a low polygon count, this is taken to the extreme here, as you
can very easily tell the difference in the models - normally the difference
would be very subtle. The third combo box deals with the resolution. The higher
the resolution the lower the frame rate, and the higher the resolution the better
quality the image is. The code automatically picks out resolutions between 600x400
and 1024x768 - as we dont want any of the weird low resolutions. It also stops
any 8bit colour modes coming through - as some graphics cards have problems
rendering in 8bit colour (and it looks really bad any way).
The next two screen
shots are from the actual program itself:
The first picture
is the low-detail version; and you can quite easily see that the torus's (donuts)
are more angular, whereas the lower picture is the high-detail version and quite
clearly looks better, and has noticably smooth curves. The colour is different
on each one because the light changes - it fades through the colours. This can
only be understood/seen by running the program.
The actual movement
of the logo is done through rotation. It consistes of a central object with
the logo as a texture, and it has 4 torus's rotating around it. All four torus's
are identical, and come from the same file (keeps down file size), but each
one is slightly bigger than the previous one. They work in pairs, the first
and third, and the second and fourth. The first pair rotates vertically, and
the second pair rotates horizontally. This creates an interesting effect, similiar
to those little models you find on peoples desks...
You can downlaod
the program from the top of the page, or from the downloads
page. Please note the notice on the options dialog - Clone Software exists,
so you cannot copy the name.
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