The Utilities Experience/The Utilities Experience - Volume 1.iso/software/rendering/utilities/imagine/softshadows/howtowhatitis.txt

Text File | 1978-06-29 | 5.6 KB | 82 lines

Are you sick and tired of Lightwave weenies with their superior attitude about
soft shadows? Specifically, the belief that Imagine cannot do soft shadows? And
does not support "Shadow Mapping"? Especially when they smugly point to Babylon5
as proof positive of Lightwave's inherent superiority? Even though there are no
soft shadows in space? Even though all of their spaceships appear to have been
made by the same shipyard? Using the same hullplates? Even though their gas
clouds and nebulae look like doo-doo compared to Imagine's Fog objects?
    Well, help is here! In fact, Imagine has had soft shadow capability from the
get-go. It is not as simple as clicking a button, however. But the trade-off for
the lack of simplicity is unlimited control over how the soft shadows look and
animate. Which would you rather have?
    This archive contains, or should contain, the following:(1) A jpeg'd picture
made of several test renderings and some rendering time and machine info.(2) A
Softlite.imp file, ready for you to put into your Imagine directory and re-
render and test render. The .imp file contains all the objects, brush maps, the
staging file, etc. and is self contained. Included among the objects are two
types of softlites, a sphere with several States, a ground, and several attri-
bute files to play with.(3) This text file :)  (4) Some screen grabs of various
Imagine screens with the settings for several of the Action and Detail editor
objects. This was done because this .imp file was done with Imagine 3.1, and I
am not 100% sure it will be completely renderable in 3.0. But you will be able
to get at the objects, especially those softlights.
    Some things to keep in mind. All soft shadowing, shadow mapping, etc., is
very processor intensive. With Imagine, the image must be raytraced. On full
screen traces with a typical flying logo expect rendering times to be about 30
minutes a frame or so. With several softlite sources, it is possible to push
rendering times well over an hour per frame. And these are 040 times! Jim Drew,
we need your 060! Also, every scene is different, so be prepared to do some test
rendering to get the look you want. And ask yourself do you really need soft
shadows for this particular project. The new Impulse light textures really do
work very well, though only on the lightsource edges themselves. And do not
forget to try experimenting with filter mapped lightsources, also.
    But assuming it's for real soft shadows you want, here's how. Basically, you
need to understand that Imagine very closely mimics the real world in it's light
ing. This may seem untrue at first, but remember that in the real world, light
does not emanate from a single point. The sun is a measurable disk in the sky,
the lightbulb in the lamp next to your computer has a sizeable surface that
actually outputs light. So the obvious solution to softlites in Imagine is to
have multiple point lightsources, the number of which is determined by distance
from the object in the scene, resolution of the image, and patience on the part
of the user that has to wait for the thing to quit cooking.
    The default lightsource in Imagine is set to 255,255,255. This is a fairly
bright white light, usually just a tad too bright for NTSC video, assuming that
the Diminish Intensity button is not clicked (sorta like sunlight). So, for a
softlite of equal brightness, you need multiple lightsources equivalent to this
value. The softlight included with this archive is made up of 25 lites set to
5,5,5 each. So one of these lights would be about half of a default Imagine
light. But Imagine allows an infinite number of lightsources. These softlites
are groups, centered around a center axis. For a normally lit Imagine scene,
you'll need two of them. Depending on the distance of the light from the objects
you will need to scale them up or down. If scaled too large, you'll see notice-
able banding around the penumbra cast by the object, if too small, the shadow
edge will be too sharp.
    These softlites were made in the Detail editor. Though you can use multiple
Stage lights, they are a real pain to position and manipulate. To change the
value of the softlites, the easiest way is to use 3.x's new Apply command. I
simply made one light, then copy and pasted it to make a group. I renamed the
center light, and made it the parent of the group. To make value changes, first
Ungroup the softlite, Pick the parent axis (light), make the changes, then do a
Right-Amiga A (the All command, in multi-select mode, using the shift key), then
do the Apply command, and all the other axes will have the same lite values.
Then re-group them, and save the object (make sure you're in Group mode).
    As stated above, this may seem like a lot of grief compared to a simple soft
shadows toggle, but consider the following. These softlites are full fledged
Imagine objects, with all that that implies. They can have States, and they can
be morphed, both positionally and attribute-wise. Consider a night-time scene
of a dimly lit seedy hotel room, with the lightsource outside the window cast-
ing soft shadows into the room. It is trivial to modify some of the lights in
the softlite group to morph to bright red, thereby simulating a flashing neon
light across the street. Or, a softlite made of cylindrical or conical lights
could be on the bottom of a spaceship that is examining something with spot-
lights, softshadowed (in an atmosphere,ok) and the lights move in different ways
after the exam is finished.
    Anyway, you can see that just about anything is possible with soft shadows
Imagine style. So now you can tell the Lightwave guys where to put it!
    Enjoy!

                                        Bill Graham
                                        [e-mail]