Frozen Fish 1: Amiga/FrozenFish-Apr94.iso/bbs/alib/d5xx/d501/genesis.lha/Genesis/Genesis_Docs

Text File | 1991-06-27 | 17KB | 315 lines

                      Using GENESIS

     These notes are just a few suggestions on how to operate
GENESIS at a basic level.  A comprehensive manual will be included
in the official release version.

System Requirements:
     An Amiga with at least 1 Megabyte of memory and AmigaDos version
1.2 or higher.  The most complex (Level 5) landscapes require about
1.6 to 2 Megabytes to create and render the landscape, depending on
the shading type and drawing mode chosen.

How a landscape is constructed:
     The basic algorithm used in GENESIS for constructing landscapes
is called the tile midpoint displacement algorithm and is described
by Mandelbrot in Appendix A of the The Science of Fractal Images, a
book published by Springer-Verlag and edited by H.-O. Peitgen and
D. Saupe.  The landscape is constructed as a grid of equilateral
triangles whose edges connect the points in the landscape.  Starting
from a single triangle, new points are added at the center of each
triangle in the landscape and around the edge of the landscape.  The
height assigned to a point is based on the average height of the
surrounding triangle plus a random fluctuation.  Two rounds of adding
points constitutes one recursion level.  The total number of points
and triangles increases by about a factor of 9 with each increase of
recursion level, with 19 points and 24 triangles at Level 1 and
about 118,000 points and 235,000 triangles at Level 5.
     At the beginning of a new recursion level, each point has a certain
probability of becoming a spring, and this "spring probability" can
be varied from one level to the next.  Rivers flow from
these springs down the path of steepest descent along the triangle
edges.  When new points are added, they are added first along the paths
of the rivers, with a random wiggling left or right at each segment
of the old river.  The random height fluctuations of new points
adjacent to the rivers are constrained to keep the rivers flowing on
the same path, which results in valleys and gullies being formed
around the rivers.

Starting GENESIS:
     Double-click on the icon.  A title screen will appear.  Menus
attached to this screen control the various operations in GENESIS.
The menus are the same as the final release version, except that
items relating to features omitted from the Demo version are
ghosted.

Action Menu

     To start constructing a landscape, select "New Landscape".  In
the final version you can initialize the random number generator
with over 2 billion seeds, but this Demo version always uses the same
seed.  A requester will appear for setting the spring probability.
Just click on "OK" to accept the default value displayed in the
string gadget.  The landscape is calculated to Level 1, and displayed
as a crude wireframe.  Blue lines indicate a point is a local minimum,
which if present at this stage will produce a very large lake (which
takes a long time to fill) at high recursion levels.  At this point
you have the option of customizing the initial landscape by dragging
points up or down with the mouse.  Click on "OK" when you are ready
to proceed.  The landscape is then redrawn with blue lines
indicating the paths of any rivers present.  You now have the option of
adding more springs to the landscape, or, by clicking on "REDO", of
eliminating all the springs.  Clicking on "OK" completes the landscape
initialization, and you are returned to the Main Control screen.
     "Increase Level" initiates increasing the recursion level by
one step.  The first requester allows you to change how running of
rivers and storage of springs is handled for the new recursion level.
Click on "OK" to proceed.  You have the option of changing the spring
probability for the new level, clicking on "OK" to accept the value shown,
or clicking on "CANCEL" to return to the old recursion level.  The
landscape begins to look respectable at Level 3.  The calculation
time and the rendering time increase by about a factor of 9 with each
increase in level, so you may want to take a look at the landscape
at Level 3 and go on to higher levels only if the landscape looks
interesting.
     "Fill Lakes" and "Run Rivers" are used to prepare the landscape
for showing the lakes and the rivers.  Filling lakes can take a long
time at high recursion levels.  All local depressions in the landscape
are found and successive iterations expand the "lakes" by raising the
water level until it reaches the height of the lowest point on the rim
of the depression, and the lake is "full".  As the calculations proceed
you are shown the number of lakes still being filled.  The process is
complete when this number reaches zero, but you can stop at any time
by clicking on "EXIT".  The lakes not yet full will be shown partially
full, and the filling process can be resumed later from where you
left off.  Clicking on "EMPTY" empties all the lakes.
     You can "Run Rivers" whether or not you have filled the lakes.  If
you don't Run Rivers, and you haven't filled lakes, when you draw the
landscape all the rivers in effect during the last increase in recursion
level will be shown as thin blue or white lines.  If all lakes are full,
none of them will be rendered as lakes unless you Run Rivers.  The
requester this selection brings up allows you to set how many rivers
from "permanent" springs will be shown and how many rivers from lakes
will be shown.  You enter the number of a recursion level for the springs,
and all permanent springs created up through that recursion level
will generate rivers.  It is usually best to enter 2 or 3 here.  The
second string gadget is where you enter the number of rivers from lakes,
with the largest lakes given priority.  The only lakes that will be
visible will be the ones not yet full and those which are sources of
rivers.
     "Draw Preview" gives you a quick preview of the picture as a crude
wireframe.  Press <RETURN> to go ahead and draw the full picture, press
<G> to bring up the Graphical view requester to reposition the observer,
or press <P> or <C> to bring up the Polar or Cartesian view requester,
respectively.  Press <ESC> or just click on the screen with the left
mouse button to return to the Main Control screen.
     "Draw Picture" draws the picture according to the draw mode
selected in the Switches Menu.
     "Quit" allows you, after confirmation, to exit from GENESIS.  You
can also just click on the close gadget of the Control Window.

Switches Menu

     The "Draw Mode" submenu allows you to change the draw mode among
three solid shaded and two wireframe modes.  "Wireframe HL" is
wireframe with hidden lines removed, and can be quite striking at
recursion levels 4 and 5.
     The options in the "Overscan" submenu are shown according to
the screen width and height in pixels in a high-res, interlace draw mode.
The physical screen dimensions are the same in the other draw modes
for each overscan option, but the width and/or height in pixels may be
less by a factor of two, depending on the draw mode.  The centering of
the screen is handled automatically by GENESIS, but once the picture
is drawn you can fine-tune the centering, if desired, using the cursor
arrow keys.  The "=WBench" option gives the picture screen the same
size and centering as the WorkBench screen, as set in Preferences in
AmigaDos 2.0 or with the program MoreRows for AmigaDos 1.2 or 1.3.
     The "Contrast" submenu only applies to solid-shaded draw modes.
"High" means a large range of brightness levels in the sun, "Low"
gives a smaller range of darker colors in the sun.  Shadow contrast
can be adjusted independently in the Colors menu.
     The "Bump Texture" submenu only applies to the solid draw modes
also.  You can toggle between two alternate types of dithering patterns
for each contour, the cliffs, and the water separately.  When a subitem
is checked, it means that landscape element will be drawn with a
fairly rough texture; otherwise, the texture is relatively smooth.  In
each case the precise texture also varies with the angle to the sun.
     The "Smoothing On" submenu is ghosted and has no effect when the
default Faceted shading is selected in the "Shading Type" submenu
immediately following.  If you select one of the three smooth shading
options in the Shading Type submenu, then the landscape elements
checked in the Smoothing On submenu will be drawn as if they are smoothly
rounded, and the others will still be drawn in Faceted shading.  The
"Best" shading type does just as good a job of hiding the triangle edges
as conventional Gouraud shading, but preserves much more of the small
bumps and gullies in the landscape.  Furthermore, if you have all three
contours selected in the Smoothing On submemu, the Best shading adjusts
the contour boundaries to be sensitive to the local curvature of the
landscape surface as well as the local slope and height, so the boundaries
are lower in gullies and hollows and higher on peaks and ridges.  That is,
with the default colors the snowline is lower in gullies and higher on
ridges.  Cliffs are more likely on peaks and ridges than in gullies or
hollows.  At the same time Contours 1 and 2 are dithered together to
give a gradual transition from "grass" to "forest".  In the final version
of GENESIS the amounts of contour dithering are adjustable independently
for the 1-2 boundary and the 2-3 boundary.
     The smooth shading options slow down the rendering considerably
compared with faceted shading at the lower recursion levels, but there
isn't much difference at Level 5.  Brightness information is calculated
and stored before the actual rendering begins, which takes about 3 times
the time required to calculate the shadows.  The additional memory
used is fairly substantial for the Best shading option, but you should
still be able to render a Level 4 landscape with 1 Meg of RAM.  The
precalculation of the shadows and brightness does not need to be repeated
for subsequent pictures of the same landscape if all you do is move the
observer.
     Choose between "Sharp" shadows and "Blended" shadows in the Shadows
submenu of the Switches menu.  Sharp shadows are recommended for Faceted
shading or for strongly front-lit scenes.  Blended shadows can produce
very striking effects in side-lit or back-lit scenes with low sun
angles.  Hills gradually dissolve into shadow as if just the tops of
trees or bushes are catching the sun.
     The "Water Shading" submenu allows you to turn water dithering on
and off for the low-res solid draw modes and water shadows on and off
for all the draw modes.  There is never any dithering for the water in
the high-res modes.  Turn shadows off to make, with appropriate colors,
the rivers be rivers of glowing "lava".
     The "WBench Open" item allows you to attempt to close the Workbench
screen while GENESIS is running, to conserve memory.  The Workbench
screen will be able to close only if no windows are open on it.

Fractal Menu

     Parameters and settings which affect the landscape generation
process.

     "Fractal Index" - set the factor by which the amplitude of the
height fluctuations is reduced during each round of adding points
(two rounds per recursion level).  Larger values mean smoother
landscapes on small scales, and smaller values mean rougher landscapes
on small scales.

     "Upward Bias" - heights of new points tend to be higher or lower
than their surroundings depending on whether this parameter is positive
or negative.  Values less than 0.5 in magnitude work best.

     "Relief Bias" - positive values mean more rugged relief at high
elevations than low elevations, as one normally expects.  If too
large, the exaggeration of relief at high elevations can become
extreme.  Set to zero to get a more hilly type of landscape.  The
High/Low option gives very smooth valleys at low elevations when the
relief bias parameter is large.

     "Meander Slope" - larger values give enhanced river meandering.

     "Rescale Old Z" - multiply all old heights by a factor without
changing the amplitude of height fluctuations at subsequent recursion
levels.

     "Jiggle On" - when checked the heights of the old points are
given a random fluctuation after each round of adding new points.

View Menu

     "Observer View" gives a choice of 3 ways of setting the observer
position and view direction.  In the Demo version, the horizontal
observer position is restricted to positions at compass angles of
0 (North), 120 (ESE), and 240 (WSW) near the edge of landscape.  You
can adjust the vertical position of the observer.  Use the Graphical
mode for these close in positions.  The red lines show the width
of the observer's field of view.  In the Polar and Cartesian modes
you can also select preset overall views of the landscape by clicking
on "747" (the default) or "U2" (a view straight down on the landscape).
The camera can be tilted, simulating the view from a banking airplane,
by setting the "Bank Angle" in the Polar view requester to a non-zero
value.
     "Camera Lens" sets the focal length (field of view) of the
camera lens.  Disabled for the Demo version.
     "Sun" - select one of 6 horizontal directions for the sun.  "Auto"
mode puts the sun direction as nearly perpendicular to the observer's
view direction on the left as possible.  Making a selection brings
up a requester to set the sun elevation angle.  Set this angle to
a small value (10 to 20) to get dramatic shadows.

Features Menu

     Parameters and settings affecting how the landscape is rendered.

     "Vertical Scale" -  resets all heights, both present and
future, without changing any height ratios.  This should be reduced
substantially from its default value when using small values of the
fractal index to keep the landscape reasonably smooth on small
scales.  Changing the vertical scale does not require refilling lakes
or rerunning rivers, but does force recalculation of shadows and
brightness values.

     "Sea Level" - Set the sea level as a fraction of the range
between the lowest height and the highest height in the landscape.
Forces recalculation of shadows.

     "Rivers" - Set parameters governing the rendering of rivers.
The larger the river depth parameter the wider the rivers will appear,
up to a maximum of about the width of a landscape triangle.  The
default gives fairly wide rivers.  The larger the waterfall slope
parameter the more the rivers will be colored as the waterfall color
rather than the normal water color.

     "Contours Solid" - set contour heights, maximum slope angles
above which triangles are colored as cliffs, and the contour
blending amplitude.  The bar at the top of the window is not a
slider gadget, but is just meant to display the relative heights of
the contour boundaries.  Set values for each contour in turn,
clicking on "NEXT" to go on to the next higher contour.  A non-zero
value of the blending amplitude makes the effective contour
boundary between the current contour and the next higher contour
depend on the steepness of the triangle as well as its height,
thereby mixing triangles of different contour colors together.
Experiment.

     "Contours Wire" - set the contour heights for the wireframe
rendering modes.

     "Resolution" - only relevant to Level 5 rendering, an
advanced feature.  The value should not differ by more than a factor
of two from 1.0.

Colors Menu

     Set the colors of the various landscape elements.  There are a
few preset colors for the solid draw modes, or you can select "Custom"
to set any color you wish.  If a wireframe draw mode is in effect,
selecting Water/Custom or Sky/Custom will bring up the RGB requester,
which has buttons allowing you to set the color of each contour as
well.  The same menu is on the picture screen, which allows you
to see immediately the effect of the color changes in the picture,
so it is best to set the colors after you draw the picture.  You
can call up the RGB requester at any time by pressing <F8>.  The
relative darkness of the shadows can be toggled between "Dark" and
"Light" values.


Picture Screen Menus

     After you draw a picture, two menus are available on the picture
screen, the Colors Menu described above and the Project Menu.  The
picture screen is automatically centered and the mouse pointer is
invisible when the picture is first drawn.  Pressing the right mouse
button or the <F10> key will shift the picture to make the menus
accessible, if necessary, and show the mouse pointer.  To re-center
the picture, press <F10>.

Project Menu

     "Hold Picture" - when checked, the picture screen is kept in
the background after you "Exit".  To recall it, press <F6>.

     "Convert to Ham" - convert the picture to Ham mode.  Only possible
for the two low-res draw modes.

     "Save Picture" - saves the picture to an IFF file.  Disabled for
the Demo version.

     "Exit" - recall the Main Control screen and its menus.  Unless
Hold Picture is checked, the picture screen is closed.  Pressing
<ESC> has the same effect.