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1994-05-09
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BLOBDRAW V1.0
5/9/94
Copyright (C) 1994, James P. Hawkins
18 Marlpit Place
Middletown, NJ 07748
All rights reserved
I. INTRODUCTION
BLOBDRAW is a freeware utility for use with Autodesk Animator Pro
software. It is written in Animator Pro's Poco programming language.
BLOBDRAW is a 2D BLOB modeling program which allows the user to
create animated or non-animated blob patterns. I was inspired to
write this program after reading the excellent article on blobs listed
below by Alfonso Hermida, who was kind enough to supply me with
sample C code for generating blobs.
Blobs are liquid-like entities which can either "attract" or "repel"
each other in accordance with their "strength" and proximity to
each other. Blobs are becoming increasingly popular in modeling
natural shapes and organic modeling such as human forms. Although
blobs can be many shapes, this program uses circular blobs only.
Blobs operate on an inverse square law much like gravity.
II. REFERENCES
"3D Artist Issue #14" PP 41, 42 Article "Introduction to Blobs"
By Alfonso Hermida
"Computer Graphics World" May 1993 PP 27-32, "The Magic of Metaballs"
by Gaye L. Graves
III. DISCLAIMER
The author makes no representations or warranties with respect to this
software or documentation, and specifically disclaims any express or
implied warranties of merchantablilty or fitness for any purpose.
Further, he reserves the right to make changes to any and all parts of
the software, at any time, without obligation to notify any person or
organizations. The author will not be liable for any special,
incidental, consequential, indirect or similar damages due to loss of
data or any other reason, even if advised of the possibility of such
damages. In no event shall liability for any damages ever exceed the
price paid for the license to use the software, regardless of the form
of the claim.
IV. SUPPORT
Please send requests, bug reports, comments to:
James P. Hawkins
18 Marlpit Place
Middletown, NJ 07748
or
Jim Hawkins at Compuserve 76520,3356
V. TERMS
Feel free to re-upload this program to other bulletin board systems
in its original, unmodified form. You may not repackage it with
other software. You may not repackage it with your own tutorial.
If you want to include this on a disk along with any magazine, book,
hardware product, or other software product, please obtain my permission
in writing.
VI. REGISTRATION
BLOBDRAW is a freeware program, but not free for resale.
James P. Hawkins
18 Marlpit Place
Middletown, NJ 07748
VII. FILES INCLUDED
BLOBDRAW.POC The POCO program
BLOBDRAW.DOC This document
VIII. GETTING STARTED
Copy the file BLOBDRAW.POC into your \ANI\RESOURCE directory.
Start Animator Pro. From the FLIC pulldown, choose RESET.
Create at least 20 frames, then from the POCO pulldown, choose
BLOBDRAW. Then, from the popup, choose DEMO.
BLOBDRAW will work with Animator Pro set to any image size, but I
recommend most experimentation at 320X200.
IX. MAIN MENU
When BLOBDRAW is invoked, the MAIN MENU appears:
1 INPUT BLOB DATA
0 DEMO
0. DEMO
Demonstration animation, a single moving blob shoots through
the area between 3 blob pairs.
1. CREATE BLOB SCENE
When this option is selected, a new menu pops up allowing the
user to set up his/her own blob scene through graphic input
and parameter settings.
X. BLOB DATA ENTRY
When "CREATE BLOB SCENE" is selected from the main menu, the
"BLOB DATA ENTRY" menu pops up with the following choices:
1 Add a Blob
2 Set Theshold Index (default = 5)
3 Set Color Mode
4 Set Palette to Grayscale
0 Go!
1. ADD A BLOB
When this option is selected, the program is waits for the user
to place a center point (x, y coordinate) for a blob with the mouse.
Upon placement of the center point, move the mouse till the
rubber circle represents the size blob you desire, then click again.
A circle will be painted on the screen and a rubber line will
form at the center of the circle for placement of the animation
path for the blob. If the right mouse button is clicked, the
line will disappear and a dot will be placed at the center of the
circle, indicating that it is a stationary blob. If the rubber
line is moved so that the other end is at the destination, clicking
the left mouse button will draw a line representing the motion path
of the blob. After entering the size and path graphically, a data
entry slider will appear called "SET BLOB STRENGTH INDEX," at which
point the user can select a new index, ranging from -10 to 10,
or simply click "OK", accepting the default of 10. The actual
index is 1/10th the slider value, hence, true strength values
for blobs range from -1.0 to 1.0.
A negative blob will be invisible, but will have a repulsion effect
on other blobs.
At this point, the BLOB DATA ENTRY menu will reappear.
Selecting "Add a Blob" will allow entry of another blob and motion
path. This may be continued until up to 100 blobs are entered.
2. SET THRESHOLD INDEX
Selecting this option causes a slider to be displayed, where the
user can select a number from 0 to 10. Each number is an INDEX
which represents a threshold value, which is 1/10th the value
of the index. (Animator Pro allows only integer slider values.)
Therefore, selecting 3 sets the threshold to 0.3.
The threshold value is the minimum value that the combined
summed strengths of blobs must exceed at a given x, y value,
to display a pixel at that point.
The default setting is 5 (threshold = 0.5).
3. SET COLOR MODE
A numerical slider appears. Giving the user 5 different methods
of determining how pixels are colored as follows:
mode 0
Uses the currently selected color to paint solid, single
color blobs.
mode 1:
Exponential function of total calculated strength according
to: color = 255 * (1 - exp(-t)).
This results in the most pleasing gradient coloring if
the palette is a gradient. The blobs are never flat-topped.
This is the DEFAULT.
mode 2:
Exponential function of total calculated strength according
to: color = 255 * exp(-t).
This results in the blobs having the HIGHEST color index
values on the outer edges.
mode 3:
Coloring as a linear function of strength. When blobs become
closely clustered, adding up to high central strength values,
flat tops occur, giving the appearance that the blobs are
liquid droplets whose tops are flattened against a flat glass
cover.
mode 4:
Coloring as a linear function of strength without flat top.
The maximum possible strength is precalculated and introduced
into the gradient. With a gradient, the more separate blobs
there are, the darker they ALL are, but if they come together,
they only reach a maximum color index of 255.
color = ((int)((t/max_strength) * 255) % 255);
4. SET PALETTE TO GRAYSCALE
Sets the palette to grayscale gradient for your convenience.
XI. TIPS
1. Use Grid... mode for more accurate placement of blobs.
2. Draw guidelines before starting BLOBDRAW to help you layout
placements and paths. BLOBDRAW will erase the guidelines when
rendering commences.
3. Create often-used guideline grids and save them in picture files
so that they may be conveniently reloaded.