Belgian Amiga Club - ADF Collection/BS1 part 19.zip/BS1 part 19/Sculpt Animate 4D v2.03 d2.adf/Henry.readme

Text File | 1988-10-19 | 11KB | 203 lines

Henry -- An Object Cycling Animation

by Marcus Brooks

Henry uses an advanced hierarchy technique, called object cycling, to
create the illusion of motion.  The idea is that there's no visible
difference (in an animation) between one object displayed first in one
position and then another, and two objects displayed, one after the
other, in different positions.

Henry has sixteen legs in any one frame, but the illusion of motion in
his legs is created by switching between eight sets of legs, one frame
after the other.  This technique is explained on page 12-14 of the
manual, but this is a step-by-step sketch of how Henry was created.

There's no need, of course, for you to re-create this animation, in
fact, it is far more involved and complex than most.  What's worse, it
seems more involved in writing than it seemed in doing.  Many handy
object creation techniques were used on it, though, so some users may
find this text to be a valuable resource.  Keep in mind that this
animation was originally created before many of Sculpt Animate 4D's
advanced features were available.  Nowadays, sizing and positioning
should be much easier, using type-in coordinates, hot-keys, etc.

This text doesn't explain how to use all the commands it mentions, the
Sculpt Animate 4D manual does that.  This file is intended to give an
example of how these commands can be put to use.  Some repeated
mechanical steps such as doing a DESELECT ALL before selecting
anything (often a necessity) are left out of the discussion.  Also
take note that scenes and portions of scenes were saved frequently to
a temporary file, as a backup.

Step by step:

1) It was decided that Henry would be an IC chip with sixteen legs that
   move in a typical centipede "wave" motion.  Since there are eight
   legs on each side, it seemed natural to use an eight-position cycle.
   This actually turned out to be a pretty coarse movement, but it's OK.

2) The "box" portion of the chip was created using normal Sculpt 3D
   techniques.  The basis was a cube, resized to proportion with
   EXPAND. "Bumper" edges were created by duplicating a parallel edge
   (just select the two vertices), this made them easier to align.
   The grabber and edgemaker gadgets were used to finish off the box.

3) One leg was created, using as few vertices as possible.  Note that
   the leg was filled by hand so that faces could be made with
   horizontal edges.  This makes the leg easier to "bend".  The leg
   was created "flat", then the top edge was bent towards the chip
   by selecting the part to bend, placing the cursor at the desired
   bend location, and using the appropriate rotate gadget.

4) The leg was copied using ADD DUPLICATE, and the duplicate placed
   next to the original using "eyeball" spacing.  Note the value of
   staying in only one window when doing this, so you only have to
   worry about alignment in two dimensions. Next, the two legs were
   selected and duplicated, and the duplicates positioned.  This made
   four legs total, these were likewise duplicated, making the eight
   legs for one side of the chip.  These are all the legs needed for
   now.  EXPAND was used to adjust the leg's spacing all at once to
   match the side of the chip.

5) An eight-subdivision circle was created, to be used as a
   positioning aid for the legs.  The circle was shaped with the
   grabber tool and EXPAND to approximate a reasonable eight-position
   motion for the leg's tip.  Three of the eight vertices were placed
   in a row "on the ground" (for better traction :).  The rotate gadget
   was used to tilt the circle at an angle from vertical, so the legs
   would swing up and out when lifted.  Again, this circle was NOT a
   path, just an aid in placing the legs.  It was erased after use.

6) The eight existing legs were positioned one by one.  First the
   placement circle was moved to a leg, set so that the bottom center
   vertex was at the point of the leg.  Then the circle was deselected
   and the point vertex selected.

   (This requires a trick, since it's  hard to select just one of
   two very close vertices.  Indicate one of the edges connecting the
   point vertex to the rest of the leg, then call SELECT INDICATED
   EDGE.  This selects the point vertex and the vertex opposite it
   on that edge.  Double-click or use the DESELECTOR tool to de-
   select the other vertex.  This should leave only the point vertex
   selected, check the status display vertex count to be sure.)

   Once grabbed, the leg's point can be moved to the appropriate
   position on the reference circle.  There are eight legs and eight
   positions, you can just "walk" down the row of legs, moving the
   circle along and placing each leg at the next position on the circle.
   This takes care of the leg's tip, but the upper part of the leg
   should bend out while the lower part swings around.  This was done
   by selecting the middle vertices of each leg and using the rotate
   gadgets in the "edge on" view to place them in a pleasing fashion.

7) This takes care of eight legs, but since there are only eight
   positions possible, all of the necessary shapes have been
   created.  The rest of the animation can be done by selecting,
   copying, and moving sets of legs, then saving them in a hierarchy.

8) The eight legs so far created were duplicated yet again, and
   the copy added on to the end, to make sixteen in a row (be patient,
   there's a method in this madness...).  Then a second duplicate
   was made (just of the eight still selected), and appended again.
   Now there were three complete leg cycles in a row, 24 legs.

9) Next, the chip body was positioned correctly next to the legs in
   the endwise view of the tri-view.  The legs were all selected
   by first doing SELECT ALL, then indicating a vertex on the chip
   and doing a DESELECT CONNECTED.  With the cursor placed as close
   to the center of the chip as possible, again in the end-on view,
   REFLECT was used to make the legs for the other side.  This
   procedure provides a proper "fit" between the legs and chip.

10) It was decided that the legs on either side should be four
    positions out-of-step with those on the other side.  This
    was accomplished simply by selecting the row of legs on one side
    and shifting it lengthwise four positions with the grab gadget.
    This left four legs "hanging" on either side, so these were
    deleted (with SELECT CONNECTED and ERASE SELECTED VERTICES) to
    make twenty pairs of legs.

11) Each pair of two legs was connected together using a single edge
    (with double-click selection and the edgebuilder gadget).  Single
    edges will not render, except in wireframe, so they may be used to
    connect things whenever you like.

12) Next, the first eight pair of legs were selected with the SELECT
    CONNECTED command.  ESC was used to call the command repeatedly,
    this key "replays" the last menu command used.

14) Once the first set of legs was selected, The cursor was
    placed precisely on a vertex of the first selected pair of legs.
    Any vertex would do, but the same one had to be used for each set.
    NAME SELECTED VERTICES was used to name this first set of legs
    "1/8legs", (see manual page 12-14 for the precise meaning of the
    numbers), then SAVE NAMED OBJECT was used to save just this set
    with the filename "legs1".  The cursor's position, relative to the
    saved object, will also be saved.  Having the cursor on a
    particular vertex will help us later.

15) Next, the first selected pair of legs was deselected with DESELECT
    CONNECTED, and the ninth pair was selected.  Think about this
    carefully.  If you consider only the selected legs, then each leg
    has advanced to the next position.  This is the whole idea.
    Again, the cursor was placed on the same vertex of the first
    selected leg.

    The newly selected set of legs were named "2/8legs", and saved in
    the file "legs2", just as above.  This step was repeated, going up
    the line of legs, until the file "legs8" had been saved.  Note
    that there were five extra legs in the "master" that never got
    saved, because they weren't needed for the loop.

16) Once the eight sets of legs had been saved to disk, all the names
    were cleared from the hierarchy using ERASE NAME in NAME SELECTED
    VERTICES, and all of the legs were erased by doing a SELECT ALL,
    deselecing the chip body with SELECT CONNECTED, then doing an
    ERASE SELECTED VERTICES.  This made the chip body the only object
    in the scene.

17) The chip's path was created simply by adding a 24 division circle
    in the "Down" window, and using DO MAKE PATH.  Then it was named
    "path" with NAME INDICATED PATH.  The chip was given the name
    "path+chip" by calling NAME CONNECTED VERTICES.  24 divisions were
    selected because that makes the take an even multiple of eight
    frames, for smooth looping.

18) The eight sets of legs were added to the hierarchy on the same
    level with "chip".  This was done with LOAD NAMED OBJECT for each
    set of legs. Before calling the LOAD command, the cursor was
    placed in the location where the "special vertex" chosen before
    should be loaded.  This ensured that it would be loaded at a
    convenient location.  As long as the legs were all loaded in the
    same place, the the chip's body could be easily repositioned.

19) A pair of eyes were made from hemispheres and placed on the chip's
    front end.  The eyes were named path+chip+eyes (chip's offspring).

20) MODIFY LOCAL ORIGIN was used to set the local origin for the chip
    and for each set of legs.  Remember, this sets the part of Henry
    that follows the path, in this case all the local origins were in
    the same place, at the center of the chip.  The legs could also
    have been made offspring of the chip, so only the chip's local
    origin would have had to be set (local origins don't count for
    offspring of vertices).  That would have been easier, but nobody's
    perfect.

21) MODIFY INDICATED TUMBLE was used to set the tumble axes along the
    path.  The chip was created facing north, so the white North
    tumble axis was set so it always points along the path.

22) The observer, lighting, and target were verified to be adequate to
    give a proper view of the path (not necessarily the chip, which can
    be placed anywhere in the global scene).  Then LOAD TAKE was
    selected to name the take "Henry".  MODIFY TAKE was called up and
    SAVE GLOBAL SCENE used to store the assemblage.  The number of
    frames was set to 24, for a smooth loop.

    A few previews and RENDER FRAMEs were tried, adjustments made, and
    changes saved with SAVE GLOBAL SCENE.  Finally, DELETE ALL IMAGES
    was used to clear the slate, and RENDER ALL was selected.

And that's all there was to it!