Python OpenGL program to generate triangle meshes of various scalar fields using the marching cubes algorithm.
The program requires pyopengl, glfw, pyglm, and numpy. For help
setting up a new Python environment and downloading the packages, check out my
beginner PyOpenGL tutorial, `Hello Triangle<https://github.com/joelenehales/hello-triangle>`_!
The program is divided into two modules to optimize performance:
| marching_cubes.py: | Generates triangle meshes and saves the data to a PLY file |
|---|---|
| render.py: | Opens the triangle mesh data from a PLY file and renders the result |
Triangle meshes are generated with the marching cubes algorithm. To generate a triangle mesh of a scalar field, execute
python marching_cubes.py filename scalar_field isovalue volume_min volume_max
stepsize| filename: | Filename of the PLY file to write triangle mesh data to.
|
|---|---|
| scalar_field: | Name of the scalar field defining the object to generate a triangle mesh for.
Options:
wavy : Scalar field f(x,y,z) = y - \sin{(x)} \cdot \cos{(z)}
hyperboloid : Scalar field f(x,y,z) = x^2 - y^2 - z^2 - z
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| isovalue: | Boundary value used to define which points are considered to be inside of the object.
If f(x, y, z) < isovalue, then the point (x, y, z) is considered to be inside of the object. If f(x, y, z) > isovalue, then the point (x, y, z) is considered to be outside of the object.
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| volume_min: | Minimum value of x, y, and z to use in the algorithm.
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| volume_max: | Maximum value of x, y, and z to use in the algorithm.
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| stepsize: | Side length of each cube in the algorithm. A smaller stepsize will result in more vertices in the triangle mesh.
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To render a saved triangle mesh, execute
python render.py filename volume_min volume_max colour| filename: | Filepath to the PLY file containing the triangle mesh's attributes.
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|---|---|
| volume_min: | Minimum value of x, y, and z in the marching volume. For best results, this should match the value used to generate the triangle mesh.
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| volume_max: | Maximum value of x, y, and z in the marching volume. For best results, this should match the value used to generate the triangle mesh.
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| colour: | Name of the object's base colour. Used as the diffuse component of the lighting model.
Options: turquoise, lime, orange, purple, fuchsia
If not specified, turquoise is used by default.
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To render the object, the program uses a Phong-like shader which combines the the ambient, diffuse, and specular components of light to compute the object's colour. A box is drawn around the marching volume, with the x, y, and z axes indicated in red, green, and blue respectively. Once the scene is rendered, the cube can be rotated in place by clicking and dragging the mouse. The camera can be zoomed in and out using the up and down arrow keys respectively.
Example PLY files that can be used to experiment with the program have been provided in the directory Example-Files. The parameters used to generate each triangle mesh are included as a comment in the file. The following images show each triangle mesh rendered. The code to generate and render each triangle mesh is included in the caption.
python marching_cubes.py Example-Files/wavy.ply wavy 0 -5 5 0.05python render.py Example-Files/wavy.ply -5 5 turquoise