Imagine 9



If you are interesting in rendering space ships with
Imagine, you will have no doubt come across quite an
iritating problem: stars.

Although the Globals menu in the Action editor contains a
star density setting, there are several drawbacks with it:

Star objects:

.. won't appear through transparent objects.
.. are all single pixels in size.
.. are all pure white.
.. refuse to animate properly.

For example, imagine that you are animating a space ship
flying past the camera. The camera pans to follow the ship,
but unfortunately the stars don't move as you pan and the
illusion is ruined. It gets worse though: the fact that the
stars are all single white pixels means that if you render
something which is to be printed the stars either look
extremely boring and flat, or even stand a very good chance
of disappearing altogether.

Solution 1

Perhaps the most solution is to use a backdrop texture
instead of the default star field objects. Depending on your
artistic abilities, or your access to NASA images, this can
be a fantastically realistic way to spice up your images.
Think of Babylon 5's lovely purple star clusters and how
they stop the images looking dull.

Here's how to add a backdrop to your images. Remember that a
neat trick is to use a backdrop you rendered previously.
This will save on rendering time. 

Step 1

Create a starry backdrop using either a paint program or by
altering an existing image. There are plenty of NASA images
around such as those taken from the Hubble Space Telescope
which are extremely colourful. It is essential to keep the
backdrop the same size as the final render, so if you plan
on rendering images of different sizes it might be a good
idea to create a large backdrop (say 640 by 512) and scale
it as needed (to 320 by 256 for example).

im10_1.iff


Step 2

Create an Imagine project, and after loading and positioning
your objects, go to the Action editor. Open the Global
settings, and enter the path and filename of the backdrop
image. 

im10_2.iff

Step 3

Render your project. You can use 256 or more colours if you like
when creating the backdrop, and Imagine will automatically
reduce (or increase) the number of colours to suit the
finished backdrop. Sometimes blurring the backdrop before
you use it can produce interesting results.

im10_3.jpg




Solution 2

The problem is of course animation: a backdrop might be OK,
but what happens when the camera changes position? Although
it's possible to animate a backdrop by providing multiple
images, trying to keep in sync with a camera movement would
be almost impossible.

The second approach then is to take background texture and
map it onto an object. This object can be shaped to suit the
animation movements. A short pan from left to right might
require a long rectangle, whilst a full 360 degree rotation
might mean that you will need to map your design into a
solid sphere and position your objects inside. This
technique has the advantage of showing through transparent
objects. Here is how to create a simple rectangular object.


Step 1

Create the image for the background. This time it doesn't
matter about the resolution of the image. Now go to
Imagine's Detail editor and create a primative plane to map
the texture on to. Notice that I've changed the size to suit
the resolution of the picture, and changed the default 10
units to only 1.

im10_4.iff

Step 2

Now select the plane's attributes, and select Brush maps.
Pick the background texture and keep to the default
settings. It's important that you make sure the object has
the BRIGHT setting on: this will prevent the backdrop from
being shaded and keep it uniform in colour. You can now save
your backdrop object.

im10_5.iff

Step 3

Turn to the Stage editor, and load in the Plane object.
Scale and position it behind the key objects in your scene,
making sure you can't see the edges. Don't use lights which
cast shadows for obvious reasons.

im10_6.iff


Step 4

If you are being really smart, you can actually use the
transparent colour option to create several layers of
backdrop for a parallex effect. Make the backdrop pattern a
Filter map and use a pure white backdrop. Now add several
laters and move them at different speeds for a really
"interest" effect.

im10_7.iff




Solution 3

This solution is my favourite, as it involves creating the
entire universe as an Imagine object. As stars are really
nothing more than points of light, there is nothing to stop
you from creating several thousand small, bright objects.
Nothing that is, except the three months it would take to do
the job properly. Imagine creating an object, copying it,
moving it and repeating it nine hundred and ninety nine
times.. they has to be an easier way.

There is a way, although it's taken me several years to find
it. I wish I had thought of it, but I didn't: I read it on
an old USENET posting so total respect to the genius who
thought it up in the first place.

Here is how to create your own universe in a minute or so.
You will need a sensible amount of memory to cope with all
this (as you might expect, the universe is a big place) so
if you get weird crashes try investing in some more SIMMS.
About 8Mb of Fast RAM and a quick 030 is good to start with.


Step 1

In the detail editor, create a primative Sphere object (hit
F5 and select the default sphere). Alter the size so that
it's about 1000 units in diameter.

im10_7.iff

Step 2

Use the Object menu, pick ADD and select AXIS. This gives
our sphere an Axis and makes it a "proper" object.

im10_8.iff

Step 3

Select both objects and use Join from the Object menu. Now
select Make Path from the menu too. This changes the Sphere
from an object, to a Path which objects can follow (this
itself is a wonderful concept to play with!)

im10_9.iff

Step 4

Now create a single star. The object has to be as small as
possible, and that means a minature pyramid. Use the Cone
primative, like this:

im10_10.iff

Step 5

Alter the atributes of the star object so that it's white
and bright. Later on you can create star objects with
different colours if you wish.

im10_11.iff

Step 6

Now the fun part. Select the star object, and then use the
Functions menu, pick Mold and Replicate. Fill in the
following settings (alter the 500 to a smaller number if you
don't have much memory). Notice how the Sphere object is the
path (it got renamed to Axis during the Join process)

im10_12.iff

Step 7

When you click on OK the star object will be replicated five
hundred times. You can now select and delete the original
path. Whooee! Look at all them stars!

im10_13.iff

Step 8

For the final step, copy the stars and paste them back again
after scaling them and rotating them. This will provide an
excellent parallex starfield effect for your space scenes.

im10_14.iff












Box out: Imagine on other platforms

Just in case you were wondering, Imagine is available on
the PC. It looks absolutely identical in all respects (not
that it was a very Amiga-friendly program to begin with) and
I tried a few test renders to see what sort of speed it
worked at. Projects and objects can be freely copied from
one platform to another. The results are very interesting,
and are for a scanline render of 640 by 480.

Amiga WarpEngine 040
PC 486DX33
PC Pentium 75