Update README and add screenshots

README.md

@@ -1,6 +1,6 @@
-Generates the shapes and then serializes them to a JSON file with a list of 
+Generates the shapes and then serializes them to a file with a list of vertices 
-vertices (`positions`) and a list of triangle faces (`cells`) that index into 
+(`positions`) and a list of triangle faces (`cells`) that index into the list of 
-the list of vertices. Suitable for input into [Three.js's 
+vertices. Suitable for input into [Three.js's 
 BufferGeometry](https://threejs.org/docs/#api/en/core/BufferGeometry) or 
 [regl](https://github.com/regl-project/regl/blob/gh-pages/example/camera.js).
 
@@ -15,3 +15,88 @@ When rendering hexspheres of detail level 5 and higher and icosahedrons of
 detail level of 7 and higher in WebGL, make sure to enable the 
 [`OES_element_index_uint`](https://developer.mozilla.org/en-US/docs/Web/API/OES_element_index_uint) 
 extension since the number of vertices might overflow the normal int index.
+
+The program can also add color to each face by assigning each vertex a color, 
+but this comes at the cost of duplicating the shared vertices in the base model 
+so each face has a unique set of vertices, greatly increasing the size of the 
+mesh.
+
+## Screenshots
+
+To generate a detailed hexsphere, it starts with base icosahedron:
+
+![icosahedron](img/icosahedron_colored_1.png)
+
+Subdivides it's sides into a more detailed icosahedron:
+
+![subdivided icosahedron](img/icosahedron_colored_3.png)
+
+Then, truncates every point in the icosahedron into hexagons and 12 pentagons:
+
+![hexsphere detail 3](img/hexsphere_colored_3.png)
+
+Up to any detail level:
+
+![hexsphere detail 7](img/hexsphere_colored_7.png)
+
+## Install
+
+To install, checkout the repo and then run `cargo install icosahedron`.
+
+## Usage
+
+Run it with the following options:
+
+```
+icosahedron 1.0
+Tyler Hallada <tyler@hallada.net>
+Generates 3D icosahedra meshes
+
+USAGE:
+    icosahedron [FLAGS] [OPTIONS] [OUTPUT]
+
+FLAGS:
+    -c, --colored      Assigns a random color to every face (increases vertices count).
+    -h, --help         Prints help information
+    -t, --truncated    Generate truncated icosahedra (hexspheres).
+    -V, --version      Prints version information
+
+OPTIONS:
+    -d, --detail <detail>    Maximum detail level to generate. Each level multiplies the number of triangles by 4.
+                             [default: 7]
+    -f, --format <format>    Format to write the files in. [default: Bin]  [possible values: Json, Bin]
+    -r, --radius <radius>    Radius of the polyhedron, [default: 1.0]
+
+ARGS:
+    <OUTPUT>    Directory to write the output files to. [default: output/]
+```
+
+## Output Format
+
+Outputs in either JSON or custom binary format. The binary format (all little 
+endian) is laid out as:
+
+1. 1 32 bit unsigned integer specifying the number of vertices (`V`)
+2. 1 32 bit unsigned integer specifying the number of triangles (`T`)
+3. `V` * 3 number of 32 bit floats for every vertex's x, y, and z coordinate
+4. `V` * 3 number of 32 bit floats for the normals of every vertex
+5. `V` * 3 number of 32 bit floats for the color of every vertex component
+6. `T` * 3 number of 32 bit unsigned integers for the 3 indices into the vertex 
+   array that make every triangle
+
+An example of reading the binary format in JavaScript:
+
+```javascript
+fetch(binaryFile)
+  .then(response => response.arrayBuffer())
+  .then(buffer => {
+    let reader = new DataView(buffer);
+    let numVertices = reader.getUint32(0, true);
+    let numCells = reader.getUint32(4, true);
+    let shape = {
+      positions: new Float32Array(buffer, 8, numVertices * 3),
+      normals: new Float32Array(buffer, numVertices * 12 + 8, numVertices * 3),
+      colors: new Float32Array(buffer, numVertices * 24 + 8, numVertices * 3),
+      cells: new Uint32Array(buffer, numVertices * 36 + 8, numCells * 3),
+    })
+```