Adding-Features.md

@@ -9,7 +9,8 @@ Adding a new problem to the code is probably the most difficult/time-consuming f
 
 To create a new problem, these are the general steps to follow:
 
-1. Create a new python file in src and name it something unique and descriptive, then go edit it
+1. Create a new branch to work in and then create a new python file in src and name it something unique and descriptive, then 
+   go edit it
 
 2. Add all relevant import statements, in all cases you will need at least these lines:
    ```
@@ -64,7 +65,7 @@ To create a new problem, these are the general steps to follow:
 
 Adding a new observer is one of the easier features to add, to do so follow these steps:
 
-1. Go to the Observers.py file in the src directory and edit it 
+1. Create a new branch to work in and go to the Observers.py file in the src directory and edit it 
 
 2. Create a new class for your observer, give it a unique and descriptive name
 
@@ -84,4 +85,51 @@ Adding a new observer is one of the easier features to add, to do so follow thes
 
 ## Adding Mesh Presets
 
-## Adding Custom Expressions
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+To add a new mesh preset, follow these instructions:
+
+1. Create a new branch and go to the MeshPresets.py file in src and edit it
+
+2. Create a new class for your mesh preset, giving it a descriptive and unique name, have it inherit from MeshFactory
+
+3. Add an `__init__(...)` method where the (...) is whatever arguments the mesh preset will need
+
+4. Determine where these meshes will be saved, in general we save all our meshes to a shared file system, so the path to your 
+   mesh's directory should start with `/panfs/pan.fsl.byu.edu/scr/grp/fslg_RFSC/new_meshes/` you then want to have a main 
+   folder where all meshes of this type will be saved, and inside of that folder each individual mesh should have it's own 
+   folder, use string formatting to create unique folder names based on what the parameters of that particular mesh are. Once 
+   you have this directory, call `super().__init__(directory)` to initialize this mesh class with a mesh at this directory
+
+5. Here you currently have two options (these instructions were last updated as of 8/26/2021), either write a string with Gmsh 
+   code in it, or create a FEniCS mesh to your specifications. Once you have done one of these options, call 
+   `super().write_XDMF_from_gmsh_code()` with the proper arguments (see [Base Classes](Base Classes) for what these are) for 
+   gmsh code, or call 'super().save_FEniCS_mesh()` with the proper arguments if you created a FEniCS mesh
+
+6. To make this mesh compatible with TDGL problems, add a function (NOT a new method) which takes in arguments of x and 
+   on_boundary. Here x is a 2D or 3D vector (depending on the dimension of your mesh) where x[0], x[1], and x[2] correspond to 
+   the x, y, and z coordinates, and on_boundary is a boolean that determines if the point is on the outer boundary of the mesh 
+   (these will both be passed to the function by FEniCS when it's determining if it should apply boundary conditions). This 
+   function should use these two arguments to come up with an expression for where the applied field should be placed on the 
+   mesh during solving. If the point in question should have field applied there, the function returns True, otherwise it 
+   returns false. Here is a simple of an example of a function which places the boundary at the top and bottom of a 1x1 square 
+   mesh with it's bottom left corner at the origin:
+   ```
+   def boundary(x, on_boundary):
+       return on_boundary and (d.near(x[1], 0) or d.near(x[1], 1))
+   ```
+   `d.near()` is a fenics function that returns True if both arguments are within some tolerance of each other (by default 
+   the tolerance is machine precision), or False otherwise
+
+7. Once you have defined this function, call `super().load_TDGL_boundary(boundary)` where here 'boundary' should be replaced 
+   by whatever you called the function. Note that if you want this function to work for both periodic and non-periodic 
+   solutions, you will need two different of these functions for each of those cases, where the periodic function does not 
+   apply field where the periodic boundary should go
+
+8. Once you are sure the mesh preset works correctly, commit your changes and merge the branch you are working on back into 
+   dev and push your changes to the remote repository
+
+9. Add your new mesh preset to the [Mesh Presets](Mesh Presets) page on the wiki and follow the same format as the other 
+   presets already there (Describe the preset and what parameters are needed for it)
+
+## Adding Custom Expressions
+
+[Ignore this section for now, custom expressions are not super fleshed out as of now]
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