Trussbox

Design from Simple 2D Constraint Solver Demo by Ange Yaghi

Preview

Montage Video (2K60FPS)

Montage (Parallel) Video (2K60FPS)

Warren Truss Bridge Video (2K60FPS)

Warren Truss Bridge Force Diagram Video (2K60FPS)

Steps

Pre-Requirements

Installation: GNU/Linux and apt package manager

Compilation: GNU/Linux and gcc-14 C23 or higher

• Recommended distro: Ubuntu 24.04 or higher

Execution: GNU/Linux and minimum 2GB memory (for 2K60FPS)

Setup

./setup.sh

Format

./format.sh

Build

./build.sh

Run

./bridges.sh

Creates solutions (videos and force data on each member and reactions on each support in the tmp directory) for each of the six truss bridges: warren, pratt, howe, parker, cambridge and whipple without further input.

or

./custom.sh

Creates solution (videos and force data on each member and reactions on each support) for a given problem containing input data for joints, members, supports, loads as well as other input data provided into standard input of the shell script (gravity, duration, frame rate, step rate, etc...).

Shell script example input:

warren.txt
9.8
3.0
10000.0
60.0
1920
1080
0.5
0.125
1.0
1.0
tmp/warren

or

./montage.sh

Usage

(low-level)

Conventions

Truss Problem Configuration

Raw text example:

joints=3
mass=1.0 position=(0.0 0.0) velocity=<0.0 0.0>
mass=1.0 position=(1.0 0.0) velocity=<0.0 0.0>
mass=1.0 position=(1.0 1.0) velocity=<0.0 0.0>
members=3
joint1=[1] joint2=[2] stiffness=3.0e3 length0=1.0 dampening=3.0e2
joint1=[2] joint2=[3] stiffness=3.0e3 length0=1.0 dampening=3.0e2
joint1=[3] joint2=[1] stiffness=3.0e3 length0=1.0 dampening=3.0e2
supports=1
joint=[1] axes={xy}
loads=1
joint=[3] force=<-10.0 -10.0>

1. Joints Count Header
   • syntax: joints=count (trailing newline)
   • number of joints in following body
2. Joints Lines Body
   • syntax: mass=float position=(float float) velocity=<float float> (trailing newline)
   • each individual joint mass in kg, position vector in meters and velocity vector in meters per second
3. Members Count Header
   • syntax: members=count (trailing newline)
   • number of members in following body
4. Members Lines Body
   • syntax: joint1=[index] joint2=[index] stiffness=float length0=float dampening=float (trailing newline)
   • each individual member joints connection indices, stiffness of spring component in Newtons per meter, resting length in meters and dampening of damper component in Newton seconds per meter
5. Supports Count Header
   • syntax: supports=count (trailing newline)
   • number of supports in following body
6. Supports Lines Body
   • syntax: joint=[index] axes={xy|x|y} (trailing newline)
   • each individual support joint binding and axes of reactions
   • if axes={xy}, support is of type pin
   • if axes={x}, support is of type vertical roller
   • if axes={y}, support is of type horizontal roller
7. Loads Count Header
   • syntax: loads=count (trailing newline)
   • number of loads in following body
8. Loads Lines Body
   • syntax: joint=[index] force=<float float> (trailing newline)
   • each individual point load joint binding and global space force vector in Newtons

Truss Solution Configuration

Raw text example:

joints=3
force=<0.000000000e+00 0.000000000e+00> position=(0.000000000e+00 0.000000000e+00) velocity=<0.000000000e+00 0.000000000e+00>
force=<0.000000000e+00 0.000000000e+00> position=(1.000000000e+00 0.000000000e+00) velocity=<0.000000000e+00 0.000000000e+00>
force=<-8.886796564e+02 -8.886796564e+02> position=(1.000000000e+00 1.000000000e+00) velocity=<-4.443398282e-16 -4.443398282e-16>
members=3
force=-0.000000000e+00 displacement=0.000000000e+00 length=1.000000000e+00 velocity=0.000000000e+00
force=-0.000000000e+00 displacement=0.000000000e+00 length=1.000000000e+00 velocity=0.000000000e+00
force=-1.242640687e+03 displacement=4.142135624e-01 length=1.414213562e+00 velocity=0.000000000e+00
supports=1
reaction=<-8.786796564e+02 -8.786796564e+02>

1. Joints Count Header
   • syntax: joints=count (trailing newline)
   • number of joints in following body
2. Joints Lines Body
   • syntax: force=<float float> position=(float float) velocity=<float float> (trailing newline)
   • each individual joint force vector in Newtons, modified position vector in meters and modified velocity vector in meters per second
3. Members Count Header
   • syntax: members=count (trailing newline)
   • number of members in following body
4. Members Lines Body
   • syntax: force=float displacement=float length=float velocity=float (trailing newline)
   • each individual member tension force (negative for in tension, positive for in compression) in Newtons, displacement from resting length in meters, current measured length in meters and velocity of expansion in meters per second
5. Supports Count Header
   • syntax: supports=count (trailing newline)
   • number of supports in following body
6. Supports Lines Body
   • syntax: reaction=<float float> (trailing newline)
   • each individual support reaction force vector in Newtons

Truss Solver

./bin/solvetruss gacceleration=float timef=float srate=float < problem.txt

• (stdin): Truss Problem Configuration
• (stdout): Truss Solution Configuration
• (stderr): error and usage messages
• gacceleration: gravitational acceleration of a free mass in meters per second squared (negative for downwards, positive for upwards)
• timef: last simulation time step time in seconds
• srate: frequency of simulation time steps in Hz

Truss Renderer

./bin/rendertruss filename fsize=widthxheight "fcenter=(float float)" fzoom=float fscale=float

• (stdin): Truss Problem Configuration
• (stderr): error and usage messages
• filename: output render png filename (image of truss in given configuration)
• fsize: renderer resolution in pixels (width and height)
• fcenter: renderer camera center in meters
• fzoom: renderer camera zoom (size of visual elements remain unaffected)
• fscale: renderer scale factor of visual elements

Truss Force Diagram

./bin/forcediagram filename gacceleration=float fsize=widthxheight "fcenter=(float float)" fzoom=float fscale=float

• (stdin): concatenation of Truss Problem Configuration and Truss Solution Configuration
• (stderr): error and usage messages
• filename: output diagram png filename (image of truss in given configuration)
• gacceleration: gravitational acceleration of a free mass in meters per second squared (negative for downwards, positive for upwards)
• fsize: diagram resolution in pixels (width and height)
• fcenter: diagram camera center in meters
• fzoom: diagram camera zoom (size of visual elements remain unaffected)
• fscale: diagram scale factor of visual elements