Light ROM 1/LIGHT-ROM 1 (Amiga Library Services)(1994).iso/imagine/text/forms.txt

Text File | 1994-10-19 | 25KB | 356 lines

Trying to Understand Imagine's Forms Editor, or, Going Mad by Degrees
by Bill Graham

    Imagine's Forms editor is probably the most ignored editor in the
program. I know of users who've used Imagine since it's release over two
years ago, and the Forms editor does not exist as far as they're concerned.
They have opened it once or twice, played with the very strange default
sphere, made some odd looking unusual objects that they could never
duplicate in a million years, and gave up feeling frustrated and
maybe a little mystified.
    The manual that ships with Imagine 2.0 makes an attempt to explain this
editor, as does Steve Worley's fine book "Understanding Imagine 2.0". With
the pending release of Imagine 3.0, and it's promised added features to the
Forms editor, those users that fall into the "Can't Deal With Forms"
category are filled with even more trepidation if they plan to upgrade.
    I am going to attempt to demystify this editor. I have taught an Imagine
class and have succesfully gotten through to people who had given up on the
Forms editor. Of course, we were all sitting in front of Amigas with Imagine
running, and I took them through it step by step both verbally and by showing
them on screen. So this will be a little more difficult, perhaps. All's we
can do is try.......

    I think what bothers most people at first is the symmetry stuff. Trying
to understand symmetry as it applies in the Forms editor can be daunting. We
will try an analogy. Think of an adjustable weight dumbbell. Imagine it
laying there on the desk in front of you. Imagine it laying in a left to
right orientation. A metal bar, with a round metal plate on either end. This
object has symmetry in all three directions. If you had a carbide blade on
a bandsaw, you could slice this object all three ways, and the resulting
halves would be equal.( Well, equal enough for this example) You could slice
it left to right, with the blade going up and down. This corresponds to
Imagine's x/z plane. We would be slicing along x, with the blade moving
along z. The two halves would be symmetrical in y. I like to think of x as
the lathe or spindle axis, y as the in/out or doorknob axis, and z as the
up/down or barbershop pole axis. If we rotated our bandsaw 90 degrees away
from us, we could still slice from left to right, but the blade would be
moving along y (the doorknob axis). The symmetry of the resulting halves
would be in z (barbershop pole). The cut is occurring in the x/y plane. Our
final dumbbell mutilation is to cut the bar in half. The blade is still
pointing away from us as in the last example, but we have to rotate it 90
degrees (doorknob). Now the cut is on the y/z plane. We cut the bar in the
middle, and the two halves' symmetry is in x. There are only three axes to
deal with. Since the hypothetical cut must involve two of them, the
symmetry or non-symmetry must occur on the other. It has to!
    Now, let us remove one of the dumbbell's plates. We slice it like we did
the first time above, left to right, into two halves, one closer to
 us than the other. Symmetry in y, yes! We rotate the blade 90 degrees, and
once again slice left to right, this time with the blade pointing away from
us as we did above, slicing it into upper and lower halves. Symmetry in z,
yes! But when we rotate the blade 90 degrees in y, and slice the bar in
half, no symmetry. By removing one plate from the dumbbell, we made it
symmetrical in two axes only.
   We are tired of this dumbbell rolling around on the desk. We go to the
sporting goods store, and buy the latest thing in work out equipment. The
triangular dumbbell plate. No more stubbed toes! But for the purposes of
this "thought" experiment, we will only put one plate on. With this funny
triangular plate attached, we slice like we did the first time above. Two
parts, one closer to us than the other. Symmetry in y, yes! We rotate the
blade away from us 90 degrees, and slice along the x/y plane. No symmetry
in z! We rotate the blade 90 degrees again, this time in y. We slice the
bar in half.(Remember, only one plate) No symmetry in x, either! Yikes!
This object is now symmetrical on one axis only.
   For our last "thought" experiment, we remove all plates from the dumbbell
bar. We stick the bar into a fist-sized blob of adhesive, fast drying clay.
We let it dry, and slice it three ways like we did above. Left to right, on
the x/z plane, no symmetry in y! Left to right, on the x/y plane, no
symmetry in z! We slice the bar up and down, on the y/z plane. No symmetry
in x either. Wow! No symmetry at all in this object.
   When you are planning to construct an object in the Forms editor, in your
mind's eye, you must determine how many axes of symmetry there are in your
object. This determines what to input into the somewhat bizarre New object
requester that you are confronted with when you start out creating a new
Forms object.
   When you are working in Forms, you have a workscreen very similar to the
Detail editor, with one major difference. The three orthogonal views
represent only part of the object you're working on. They are actually an
abstraction of the object itself, as opposed to a wireframe of the object
that you see and work with in Detail. But to start working, you must
satisfy the new object requester, which will be explained now. Contrary to
what has been written elsewhere, you should never use anything but the
default Two Former views. In fact, in earlier versions of Imagine, you had
no choice. Two Former was it. I say this because now that you understand
symmetry, there is no need for you to work in the other two modes. They are
actually "restricted" modes, for remedial Imagineers. They actually
restrict axes of symmetry (there's only three, for God's sake), and you will
be seriously restricting yourself if you use them. So I will not be covering
these other two modes. Try them if you like. But it's sorta like learning
to drive on an automatic, and then trying a stickshift. It can be done, but
it's a lot harder. So be cool, and use Two Former views.
   When first learning your way around Forms, leave the default number of
Points and Slices, or input a smaller number. It's always easier to add
points as you go. Points and Slices are easy to explain. If you were going
to make a candlestick holder, Points would be the number of editable points
around the circumference, and Slices would be the number of editable slices
along the length of the holder. X-Y Cross section would be selected if you
were going to make your holder right side up. Y-Z Cross section would be
selected if you were going to make it laying on it's side. When you click
one or the other, the corresponding Seal Top End and Seal Bottom End buttons
become Seal Right End and Seal Left End. The default is fine when you're
learning. You see, the sphere you get when you create a new Forms object is
not really a sphere. It is a spherical cylinder. It is actually a tube, with
the number of slices and points specified in the cross section fields, and
Seal XXX End simply adds a central point with faces that close off the tube.
  These ends will not be "flush" with the normal end of the objects, and you
cannot edit this single point directly from Forms. It is a job for the Detail
editor.
   In terms of learning to create objects, it doesn't really matter which
cross section selection you choose, object editing is the same either way.
Later on, when you are comfortable with Forms, it will matter, in terms of
making morphable objects and such.
   This spherical tube concept is important, because that is the key to
understanding how to work in Forms. Basically, in the three non-perspective
views, you are working with one cross section view of the spherical tube, and
two silhouette views. Which of the Top,Front, and Right views is what
depends on which Cross section orientation you select in the New Object
requester. Your choices are two, X-Y and Y-Z. Which axis is common to those
two choices? Y, of course.(no pun intended). Looking at Y (doorknob) is
always the Front view. And the Front view never changes, in that it always
is represented by a broken circle. The orientation of the break(s) always
corresponds with the Cross section axis. If the Cross section selected is
X-Y (tube running top to bottom), then the breaks in the Front view circle
are the top and bottom. If the Cross section selected is Y-Z (left to right),
then the breaks are on the left and right.
   The Cross section view, however, can be either the Top or the Right view.
And the Cross section view is always easy to identify, because it is always
the unbroken circle. So if you pick the up/down orientation, the Top view
will be the Cross section view. And if you pick the right/left orientation,
the Right view will be the Cross section view. Hopefully, this Forms editor
seems a little less formidable by now.
   When working in Forms, you are working on a series of Cross sections,
of which only one is visible at a time. For a Cross section to be editable,
it has to be a Key Cross section. The default object always only has one of
these Key Slices. Later, we will learn how to add more. But for now, you
should be able to understand that when you create an object in Forms, you
are working on a series of cross sections, with corresponding silhouette
points in the other two views. Like the sections of an extruded object, for
instance.
   The only other selection to make in this now-not-so-nasty requester is
Fixed Cross Section Symmetry. From earlier in this text you should
remember that there are only three possible axes of symmetry. Since we are
dealing with a cross section of a three dimensional object, we only have to
worry about two axes of symmetry. Which two, of course, depends on which of
the X-Y or Y-Z choices you choose. These buttons, like the Seal XXX End
buttons, will change depending on which orientation you click. (Remember,
this requester is for the Cross sections ONLY!) Cross section symmetry is
always (almost) fixed. Should you be in the midst of editing, and decide
you don't want that fixed symmetry, you (a) save the object, (b) start a new
one with the same cross section points and same form, only with the new one
selecting None in this requester. If we were to accept the default, our cross
section would be in the Top view. X axis would mean that moving a point on
the left would move the corresponding point on the right. ( You must mentally
divide the cross section into halves, it isn't marked for you.) Y axis would
do the same for the top and bottom. Both Axes move the three other corresponding
points. Try this once or twice and it'll make perfect sense. Remember, with
None selected, just the cross section point you actually work with will move,
with X axis or Y axis, you get two for the price of one. With Both axes, you
get four for the price of one. So for a candlestick holder cross section, you'd
choose both, for a boat hull or a carving knife, you'd choose X or Y, and for
something organic like a leg or an arm you'd choose none.
   And this wraps it up for the dreaded New object requester. Almost, anyway.
I will leave it as an excercise for the reader to figure out the Ok and
Cancel buttons.
   I will now attempt to explain the menus. The Project and Display menus are
pretty self explanatory. They work much like their counterparts in the other
editors. The Object menu is pretty similar also, with a couple of important
differences. There are only four commands here. We've already covered what
the New command does. Load does the obvious, it loads an object. You can only
work on one object at a time. And the object you load MUST be an object that
was created here in the Forms editor. Once you've modified an object in the
Detail editor, it loses it's special internal description that makes it a
Forms object. In order to maintain the special symmetrical editing capabilities
the Forms object must remain unaltered if you want to edit it further in
Forms. For this reason I always append a suffix such as .frm to these objects,
and save it under a different name from Detail. I suggest you get into this
habit also, because once the object is altered that's it! Save is easy enough
to figure out. Snap to Grid allows you to select one or more points in the
various views and have them all align to the nearest grid intersection. When
you become familiar with the Forms editor, this command will be very helpful
for assuring selective editing point symmetry.
   The Mode menu is simple to understand. There are three basic things you
can do to an objects' points, and those three are Edit, Add, and Delete. You
cannot Delete an object to nothing but a simple axis here as you can in Detail,
nor can you Delete an objects defined Key slices. When Adding points, be
careful not to get lost. It is very easy to be in Add mode and forget to
switch to Edit mode, thereby Adding several unwanted points/slices to your
object. I recommend Adding then Editing one point at a time when you are first
learning your way around Forms. This is because what happens to the Added
editing point is not always apparent. You will always see the adjoining
connected lines "jump" when you Add a point. But sometimes you don't see the
point itself. This has made many users crazy. The fact is the new point is
always there, but what happens to it when it's first added is determined by
many factors. These factors include whether you are working in a Cross
section view or a silhouette view, what fixed symmetry is in place (determined
by the New requester), whether you have Locked selected in the Select menu,
whether the adjacent point is a Key slice or not, whether it's raining in
London or not, whether you prefer dogs over cats, whether you live in a
community property state or not, and things like that. What you need to remember
is this: The point is ALWAYS present. If you can't see it, it is either
"underneath" the nearest point you clicked close to, or "underneath" one of
the two adjacent points. It will ALWAYS be under one of those three points.
Sometimes when you Add a point, you will actually be adding two, or sometimes
four points, and instead of losing just one point, you've lost two or four.
But this is no reason to freak, because when you find one, you'll also find
the corresponding second and third/fourth point. Just remember what I said
about adjacent points above. Much more of the reasoning behind this wierdness
will become apparent when we discuss the Symmetry menu, coming up next.
   The Symmetry menu is in many ways the meat and potatoes of the Forms editor.
It has also caused a lot of confusion, because when you look at the various
Symmetry selections, you realize you've seen much of this before in the New
object requester. But the New object requester only addresses symmetry in the
Cross section view. The Symmetry menu addresses symmetry in the two "silhouette"
views. These two views are determined by the New object settings, as you
should remember. With the default settings, the silhouette views are the
Front and Right views. The first Symmetry setting is Off. This means that
when you edit a point in either of the silhouette views, only that point is
affected. The corresponding point remains unchanged. If you were modeling a
candlestick holder with the Off setting selected, it would look very
strange because it would not look "spun" as it should. But if you were model-
ing a carving knife (oriented up and down with the default settings), this
is what you'd want, assuming you were using the non symmetric silhouette
view for the knife's flat outline. Front view and Right view (or Top view, as
this changes according to the New requester settings) means that when you
edit a point(s) in that selected view, the opposing point(s) move also. These
two settings establish symmetry in their respective views. So with just one
or none of these selected, it is possible to move editing points so that they
are not "lined up". For many "organic" objects, this is precisely what you
want. This also allows you to put detail where it's needed, while keeping an
eye on object size. The Both setting simply sets up non-concurrent symmetry
in both silhouette views. So when you edit points in the Front view, only
Front view symmetry is in force, and when you edit in the Right view, only
Right view symmetry is in force. But the other silhouette view is not directly
affected. The 90 Degree setting, however, does establish dual silhouette
view symmetry. So when you edit a point in the Front view, the Right view
points move also, and vice versa. I know this sounds confusing, but when you
try it (on SIMPLE objects when learning) it really will come together.
  The Select menu has four settings that look very similar to those in the
Detail editor, but actually they behave very differently. Click mode functions
like Drag Points mode in the Detail editor. You click on a point with the
left mouse button, and while holding down that button move the point to where
you need to. All Select settings work in the Cross section view as well as
the silhouette views. Click mode also supports the "multi" option by holding
down the shift key while clicking multiple points. Drag Box and Lasso are
both multi-select options, you drag-box or lasso points while keeping the
shift key pressed, then release the shift key while holding down the left
mouse button to move the points. It will become obvious to you that by doing
this you can make truly radical changes in your object very quickly. Lock
means that when you move a point or points, they will automatically snap to
the nearest grid intersection. This is a more controlled way of doing the
Snap to Grid function of the Object menu, as you can toggle this on or off as
needed.
   The Cross Section menu is the last of the Forms editor menus ( as far as
Imagine 2.0 is concerned). When you first create a new Forms object, the
spherical tube only has one defined cross section, so when you select the
Select command the first time, you'll get a box that tells you "The current
cross section is the only one defined". Once you define more than one Key
cross section, the Select command will highlite in orange all defined Key
cross sections. This ability to define key cross sections is something that
does not exist on any other grphics platform. Imagine smoothly interpolates
between cross sections, making a natural, realistic transformation from one
cross section shape to another. The cross sections have to be selected from
 one of the silhouette views, because only one cross section is viewable at
 a time. The program automatically numbers these cross sections, and it is
displayed at the top of the screen. The way to make a new cross section is
with the Make Key command. In a new object, the one pre-defined cross
section is always at the end of the "tube". After selecting Make Key, you
simply click on a point in one of the silhouette views and that cross section
becomes a Key section. You can verify this with the Select command. Once you
have made a new cross section, that is the one represented in the cross
section view. For instance, after accepting the default settings in the New
object requester, select Lock from the Select menu, and select 90 degree from
the Symmetry menu. In either of the silhouette views, start moving points on
one half of the broken circle so that they elongate into a straight line with
the points locking to the grid intersections. It makes no difference how
short or tall the resulting tube will be. This is just to illustrate a point.
Once you have your tube (it'll look like a tube in the perspective view), go
ahead and admire it for a while. Now select Make Key from the Cross Section
menu. In one of the silhouette views select a cross section towards the
middle of a tube. The lines will jump but nothing will seem to have changed.
But something has changed. Select Select from the Cross section menu, and
you'll notice two pairs of control points in the silhouette views turned
orange. Go ahead and click the new one you just made (it's already selected
but this helps you practice). Play with the cross section view points, turning
Lock on and off and moving the points around. In the perspective view, you'll
see that the tube stays round at one end, but gets wierd in the middle. Also,
try to make the new cross section "small" by putting the points close
together. It does not behave as you'd think because the cross section view
has nothing to do with the size or circumference of a part of an object,
only it's shape. We'll get to size changing and stuff in a minute. Now make
a new cross section, this time on the opposite end of the tube. If you
verify this operation with the Select command, you'll see a total of three
cross sections, with three pairs of orange points in the silhouette views.
Now select the newest cross section, and from the Cross Section menu select
Copy From. At the top of the screen you'll see the message "Select Cross
section to Copy From". Select the original, round, default cross section.
You'll see that the tube is round at both ends, and warped in the middle.
Select Unmake Key from the Cross Section menu. Click the middle cross section
in one of the silhouette views. Now you have a round tube from end to end
again. Play. Experiment. Be strange. By making and unmaking cross sections
and changing their shape, you alter the "long axis" basic shape of the
object. By moving points around in the silhouette views, you change the
silhouette shape and diameter of the object. You can have as many or as few
cross sections as you want, adding and deleting as needed. But always, always,
only one cross section can be edited at a time, while an entire silhouette is
visible at once.
   When working in the various views, once again depending on the current
settings, you will notice "rubber band" lines going from the points you're
editing towards the center of the representative view. These are guides to
tell you where the corresponding points are in the other silhouette view.
Using Forms depends very much on your ability to visualize, and relies more
on intuition (the human kind) more than any other editor. Although it seems
odd to work with at first, after a while you will find yourself starting
most of your projects here. There are some oddities about Forms objects, and
I also have some tips on object creation.
   Forms objects are of a different structure than other Imagine objects.
This stucture is modified by the application of attributes in the Detail
editor, and this will suffice to keep the object from being re-edited in the
Forms editor. But the simple addition of Attributes alone is not enough to
make the object a complete Imagine object. Oh, it'll render and animate just
fine, but it'll not be readable by the various file format conversion
programs available, or any of the third party object editors. Also, these
objects, when further deformed by the Mold operators in the Detail editor,
will not retain the deformation. You'll see it deform, and you can save it,
but when you bring it back into Detail, you'll find that the deformation did
not stick! In order to make these objects into full fledged Imagine objects,
you must "break" the object geometry symmetry. You do this by going into
Pick Point mode in Detail, and moving just one (or more) object point. The
distance moved can be tiny, and it isn't important which point is moved. But
you have to do this if you want to export your object.
  When creating two or more objects to be morphed, make the most complex
object first. Then you can combine points for the simpler objects. Be sure
not to delete or change the number of slices or cross section points, if
you do the object will not morph. Do not use the Merge function in Detail in
order to simplify your object, it'll blow the concurrent point/edge requirement.
For the same reason, don't take the object into another program for editing
or whatever, the objects structure would be destroyed, and even if you end
up with the correct number of points and edges, the point order will be fried,
and it'll look like spaghetti when you try to morph it.
 If you're willing to put in some time, incredible transformations are
possible. All the letters of the alphabet can be made with the exception of
the uppercase "B", which requires two objects. But you can morph letters into
other letters. Remember, ThreeD letters are always symmetrical in at least
one axis (depth). And some are symmetrical in three axes (o).
  Take the time to break things down, and use a little imagination. Break a
butterfly down into head, big wings, little wings, thorax, abdomen, and
with Forms make them along with the propeller, big wings, little wings,
fuselage, and tail fin of an airplane. Morph them while flying, maybe
concurrent morphing of cycles also. Your imagination is the only limiting
factor.
   I hope this effort takes some of the pain out of learning the Forms
editor. And remember what the Arby's commercial says! "Different is Good!"
And remeber what Mr.Wizard used to say ( the cartoon character, not the
science teacher) "Be vat choo iss, not vat choo iss not!" Have fun....
                                            Bill Graham