3D Real-time Dynamic Muscle Demonstration July, 2000

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This demonstration builds on the spring-mesh system I built last

year by making some of the springs active.

In this demo, each Muscle is activated by a periodic function

(a sin wave with 256 emtries in this case). The muscle has a contraction

percentage and an offset into the wave table. The offset allows

muscles to be activated at different times.

For example, on the dolphin that is included, there are four muscles

controlling the tail. Two along the top and two on the bottom that

alternate activating.

To change a spring to a muscle, select the two vertices connected by a

spring and selecting "Spring/Muscle Settings" from the Simulation menu.

Make the muscle active and give it a contraction value.

To load new models, load them as an OBJ as described below then connect

it with springs.

Todo:

Try different activation functions (a square wave would be easy and interesting)

Apply the viscous force to the model as described in the article

Jeff

v. 1.0 Jan 1999

Soft body dynamics

This program simulates soft body dynamics of a particle system

with particles connected with springs.

This program is fairly complicated. In order to show off the

features I wanted to demonstrate, I needed to create quite a

number of functions and UI. I appologize for all the extra junk

but it was as clear as I could make it in the time allowed.

All the major functions for the actual dynamic simulation are in

the files: PhysEnv.h and PhysEnv.cpp. Some of the timing

and display code is in OGLView.h and OGLView.cpp. Most of

the UI is passed through MainFrm.cpp to OGLView.

All of the simulation constants can be set through the

Simulation Properties dialog. Any changes to the spring constants

are applied to all springs in the simulation. There is currently

no way to change the settings for an individual spring.

You can load in one of the pre-made simulations or create a

new one by loading in an OBJ. The OBJ needs to be scaled

within a +-5 unit cube world so it fits within the world boundaries.

An OBJ file loads as a point cloud. You then can connect the dots

by selecting vertices two at a time. Press "ENTER" to connect the

points with a spring. The normal length of the spring is the distance

at the time of spring creation.

You can select one or two vertices and apply an user force to

the selected vertex/vertices. Once selected, a user force is

applied with the arrow keys for X-axis and Z-axis and HOME/END

applies the force to the Y-axis. The magnitude of the user force

is set in the sim properties dialog.

You can also click and drag the LMB to apply a force in the local

X and Y axis. The mousespring force is set in the sim properties

dialog. The force will apply to the one or two vertices selected.

Demos:

Jeff Lander

jeffl@darwin3d.com

www.darwin3d.com/gamedev.htm

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I compiled the code with Visual C++ 6.0. It has been tested

with Microsoft OpenGL, SGI OpenGL for Windows, Permidia 1 and 2 OpenGL

Drivers, Riva 128, TNT, TNT2, AccelGalaxy,

and Symetra Ultra FX Pro.

It should run on any OpenGL fully complient driver. This

DOES NOT include the mini-QuakeGL driver for 3DFX. 3DFX

OpenGL does not support OpenGL in a window so will not work

with this application.

Also, depending on how well GLlines are drawn on your system, the

sim should run too fast, too slow, or just right. I try to lock

it to the clock except to set the timesteps. If it is strange,

adjust COGLView::RunSim().