106 lines
3.9 KiB
Markdown
106 lines
3.9 KiB
Markdown
Generates the shapes and then serializes them to a file with a list of vertices
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(`positions`) and a list of triangle faces (`cells`) that index into the list of
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vertices. Suitable for input into [Three.js's
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BufferGeometry](https://threejs.org/docs/#api/en/core/BufferGeometry) or
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[regl](https://github.com/regl-project/regl/blob/gh-pages/example/camera.js).
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Icosahedrons can be generated significantly faster than Three.js's version in
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JavaScript (which I pretty much copied into Rust).
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Trunacated icosahedrons (I call them hexspheres) are a bit slower to generate
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since they are made by generating a icosahedron and then truncating every point
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into hexagon and pentagon faces.
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The program can also add color to each face by assigning each vertex a color,
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but this comes at the cost of duplicating the shared vertices in the base model
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so each face has a unique set of vertices, greatly increasing the size of the
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mesh.
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When rendering hexspheres of detail level 5 and higher and icosahedrons of
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detail level of 7 and higher in WebGL, make sure to enable the
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[`OES_element_index_uint`](https://developer.mozilla.org/en-US/docs/Web/API/OES_element_index_uint)
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extension since the number of vertices might overflow the normal int index.
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View the shapes in 3D at: https://www.hallada.net/planet/
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## Screenshots
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To generate a detailed hexsphere, it starts with base icosahedron:
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Subdivides its sides into a more detailed icosahedron:
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Then, truncates every point in the icosahedron into hexagons and 12 pentagons:
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Up to any detail level:
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## Install
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To install, either run `cargo install icosahedron` or checkout the repo and run
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`cargo build --release`.
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## Usage
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Run it with the following options:
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```
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icosahedron 0.1.1
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Tyler Hallada <tyler@hallada.net>
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Generates 3D icosahedra meshes
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USAGE:
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icosahedron [FLAGS] [OPTIONS] [OUTPUT]
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FLAGS:
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-c, --colored Assigns a random color to every face (increases vertices count).
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-h, --help Prints help information
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-t, --truncated Generate truncated icosahedra (hexspheres).
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-V, --version Prints version information
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OPTIONS:
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-d, --detail <detail> Maximum detail level to generate. Each level multiplies the number of triangles by 4.
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[default: 7]
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-f, --format <format> Format to write the files in. [default: Bin] [possible values: Json, Bin]
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-r, --radius <radius> Radius of the polyhedron, [default: 1.0]
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ARGS:
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<OUTPUT> Directory to write the output files to. [default: output/]
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```
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## Output Format
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Outputs in either JSON or custom binary format. The binary format (all little
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endian) is laid out as:
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1. 1 32 bit unsigned integer specifying the number of vertices (`V`)
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2. 1 32 bit unsigned integer specifying the number of triangles (`T`)
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3. `V` * 3 number of 32 bit floats for every vertex's x, y, and z coordinate
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4. `V` * 3 number of 32 bit floats for the normals of every vertex
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5. `V` * 3 number of 32 bit floats for the color of every vertex
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6. `T` * 3 number of 32 bit unsigned integers for the 3 indices into the vertex
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array that make every triangle
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An example of reading the binary format in JavaScript:
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```javascript
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fetch(binaryFile)
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.then(response => response.arrayBuffer())
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.then(buffer => {
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let reader = new DataView(buffer);
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let numVertices = reader.getUint32(0, true);
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let numCells = reader.getUint32(4, true);
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let shape = {
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positions: new Float32Array(buffer, 8, numVertices * 3),
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normals: new Float32Array(buffer, numVertices * 12 + 8, numVertices * 3),
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colors: new Float32Array(buffer, numVertices * 24 + 8, numVertices * 3),
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cells: new Uint32Array(buffer, numVertices * 36 + 8, numCells * 3),
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})
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```
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