Tresta

Getting started

The project requires Qt and CMake. If not installed, please install both before continuing.

To compile the code:

1. Open the tresta root directory.
2. create a folder named build.
3. Open a terminal and navigate to the newly formed build directory.
4. Execute cmake .. -DCMAKE_PREFIX_PATH=/path/to/qt. * By default this will build Tresta in release mode. Use -DCMAKE_BUILD_TYPE=debug if you would like to build the code for debugging purposes. * -DCMAKE_PREFIX_PATH=/path/to/qt tells CMake where to find the Qt installation. For example, on my computer this would be set to /home/ryan/Qt/5.5/gcc_64.
5. On Linux run make in the terminal from the build directory to build all the targets. On Windows the solution file will be located in the build directory. Open the solution file in Visual Studio and compile.
6. Upon successful compilation the tresta binary should be located in build/bin/

Introduction

This program is used for visualization of 3D truss structures. A truss is defined using CSV files to specify nodal positions, connections between nodes (elements), elemental properties, and (optionally) displacements. The path to each of these files is specified using a JSON document. For example,

{
    "nodes" : "/path/to/nodes.csv",
    "elems" : "/path/to/elems.csv",
    "props" : "/path/to/elems.csv",
    "colors" : "/path/to/colors.csv"
    "displacements" : "/path/to/displacements.csv"
}

This configuration file is used by tresta to load the structure. After launching the tresta binary, open a valid configuration file to display the structure. The "nodes", "elems", and "props" keys must be present. The "displacements" and "colors" keys are optional. If "displacements" are provided then both the original and deformed truss structures are rendered. The "colors" key can be used to set RGBA colors on an element-by-element basis. If not provided, a single color is used for the original and deformed meshes.

CSV files

All CSV file must be comma delimited with no spaces between values, i.e. one row of the nodal coordinates file might resemble 1.0,2.0,3.0.

Nodes

The nodes CSV file specifies the x, y, z coordinate of each node in the truss. The format should be:

x1,y1,z1
x2,y2,z2
...
...
...
xN,yN,zN

where each entry is a floating point number and every line must have 3 entries for the x,y,z position.

Elements

The elements CSV file specifies which nodes are connected. Each element is comprised of two nodes, and each node is referenced by its index in the nodes CSV file, i.e. if there a strut between the first and second node in nodes.csv the first line in elems.csv would be 0,1. Nodal indices are zero based and incremented by row. The format of the element CSV file should be:

el1_node_num_1,el1_node_num_2
el2_node_num_1,el2_node_num_2
...
...
...
elN_node_num_1,elN_node_num_2

Properties

Each row in the elemental properties file must have at least 3 values specifying a normal vector parallel to the beam's local y-axis. If there are more entries in each row the parser discards that information and takes the last 3 entries in each row as [nx, ny, nz] components. floating point values in the form:

...,el1_nvec_x_comp,el1_nvec_y_comp,el1_nvec_z_comp
...,el2_nvec_x_comp,el2_nvec_y_comp,el2_nvec_z_comp
...
...
...
...,elN_nvec_x_comp,elN_nvec_y_comp,elN_nvec_z_comp

where el1_nvec_y_comp is the y-component of element's normal vector, and el1_nvec_z_comp is the z-component of element's normal vector. The normal vector is defined as vector of unit length pointing along the beam's y-axis.

Colors

Explicitly setting the colors is optional. This is ideal when you need to set color on an element-by-element basis, e.g. applying a color map to the structure. If the "colors" key is not provided original and deformed colors can be set after opening in the toolbar, but the color will be applied to the entire mesh. Each row in the colors.csv file must have 4 floating point values on the range [0.0,1.0] specifying red, green, blue, and alpha values, respectively. If the "colors" key is provided, then it must contain the same number of rows as the "elems" key, i.e. all elements must be given a color. For example if there are N elements, a sample colors.csv would have the form:

r_el1,g_el1,b_el1,a_el1
r_el2,g_el2,b_el2,a_el2
...
...
r_elN,g_elN,b_elN,a_elN

Displacements

Displacements are optional, but if provided allow visualization of the deformed truss structure. This file will, in general, be computed by a finite element analysis (see threed-beam-fea). The format is such:

dx_1, dy_1, dz_1, rx_1, ry_1, rz_1
dx_2, dy_2, dz_2, rx_2, ry_2, rz_2
...
...
...
dx_N, dy_N, dz_N, rx_N, ry_N, rz_N

where dx_1, dy_1, and dz_1 are the translational displacements applied to node 1 in the x-, y-, and z-directions, respectively, and rx_1, ry_1, rz_1 are nodal rotations about each global coordinate axis.

Example

After a successful build, launching the tresta binary will open a window similar to:

Either pressing the open icon or clicking on the file menu and selecting open will allow you to choose a configuration file. An example configuration file is in the examples folder. Before opening with tresta, change the path specified by "nodes", "elems", "props", and "displacements" to the correct path on your computer. By default the keys are specified relative to the default output path of the tresta binary (assuming that you placed the build output in a subfolder of the tresta root directory). If the executable is placed somewhere else, tresta will not find the files without modifying the paths in config.json. After selecting to open the properly configured config.json file the following should open:

The deformed shape is shown in red, and the original shape is shown in blue. In the case of the example, this is the result of crushing the simple cubic truss axially along the x-axis. For more information on specific controls click the about dialog from the help menu of tresta.