Write docs on creating a single object

src/blenderbim/docs/devs/hello_world.rst

@@ -40,10 +40,19 @@ Just show me the code!
 ----------------------
 
 Sometimes, the best way to learn how to hack on a project is to just start
-hacking away. BIM authoring is a really big topic. As a result, the BlenderBIM
-Add-on code is separated into modules. Each module focuses on a particular topic
-of BIM. Most modules are self-contained, but sometimes they connect to one
-another, just like how BIM works.
+hacking away. First, download the code. To keep things simple, you can download
+the source as a zip file for now, but keep in mind that sooner or later you'll
+need to :ref:`use Git to collaborate <submitting-code-to-git>`.
+
+.. container:: blockbutton
+
+    `Download Source
+    <https://github.com/IfcOpenShell/IfcOpenShell/archive/refs/heads/v0.7.0.zip>`__
+
+BIM authoring is a really big topic. As a result, the BlenderBIM Add-on code is
+separated into modules. Each module focuses on a particular topic of BIM. Most
+modules are self-contained, but sometimes they connect to one another, just like
+how BIM works.
 
 .. image:: module-architecture.png
 
@@ -282,6 +291,29 @@ The code for IfcOpenShell's various systems can be found here:
 - `ifcopenshell.util <https://github.com/IfcOpenShell/IfcOpenShell/tree/v0.7.0/src/ifcopenshell-python/ifcopenshell/util>`__
 - `ifcopenshell.api <https://github.com/IfcOpenShell/IfcOpenShell/tree/v0.7.0/src/ifcopenshell-python/ifcopenshell/api>`__
 
+.. _submitting-code-to-git:
+
+Submitting code to Git
+----------------------
+
+So, you've written some code, fixed a bug, made an improvement, and would like
+to get your code added to the Git repository? If your change is relatively
+small, you can submit your changes just using the Github website. Browse to the
+`IfcOpenShell repository <https://github.com/ifcopenshell/ifcopenshell>`__ and
+navigate to the file you want to edit the code of. Then just press the edit icon
+to begin editing. When you're done, you'll be prompted to submit your changes.
+
+.. image:: github-editing.png
+
+If you're making a large change, you'll need to create a **Pull Request**.
+Github has an excellent comprehensive guide on `how to contribute to projects
+<https://docs.github.com/en/get-started/quickstart/contributing-to-projects>`__
+which you can follow.
+
+If you make regular contributions, you are also welcome to officially join the
+IfcOpenShell developer team, where you'll be able to make changes without
+waiting for code reviews and approvals.
+
 Asking for help
 ---------------
 

src/blenderbim/docs/index.rst

@@ -15,7 +15,7 @@ The BlenderBIM Add-on lets you analyse, create, and modify OpenBIM with Blender.
    users/introduction_to_bim
    users/installation
    users/exploring_an_ifc_model
-   users/creating_your_first_ifc
+   users/creating_an_ifc_model
    users/georeferencing
    users/dealing_with_large_models
    users/other_addons

src/blenderbim/docs/users/creating_an_ifc_model.rst

@@ -0,0 +1,79 @@
+Creating an IFC model
+=====================
+
+We're going to create a new native IFC model from scratch, starting from a
+single shape, up to a simple building.
+
+A BIM model is not just a 3D format. This means that you cannot just load any 3D
+model, and press a "Save as IFC" button. In fact, 3D is optional and you
+can have a large IFC model storing work schedules, cost rates, asset registers
+and more, and absolutely no 3D geometry at all.
+
+However, in these tutorials, we will focus on basic 3D geometry. At a minimum,
+you will need to categorise your 3D elements (such as "Wall", "Column",
+"Window", etc), and give them a location (such as "Level 01" of a building).
+
+Creating a single object
+------------------------
+
+In the **Properties** panel in the bottom right, activate the icon for the
+**Scene Properties** tab, and find the **IFC Project** subpanel. Click on
+**Create Project** to create a blank IFC project.
+
+.. image:: create-project.png
+
+For convenience, this IFC project by default defines length, area, and volume
+units, and assumes you'll be working with both 2D and 3D geoemtry.
+
+In the top right **Outliner** panel, you will see a hierarchy of spaces that has
+been automatically created for you.  This hierarchy is known is the **Spatial
+Tree**.
+
+.. image:: default-spatial-tree.png
+
+Any Blender object that you want to part of your IFC project must be converted
+into a IFC object by assigning a category. This category is known as the **IFC
+Class**.
+
+Select only the default Blender Cube (selected objects are highlighted in
+orange, careful not to select anything else!), switch to the **Object
+Properties** tab, and find the **IFC Class** panel. Let's pretend our Cube is a
+column, so select **IfcColumn** from the **Class** drop-down, and press **Assign
+IFC Class**.
+
+.. image:: assign-class.png
+
+All IFC objects must also belong inside the **Spatial Tree**. In the
+**Outliner** panel, you can drag and drop your newly created **IfcColumn/Cube**
+inside the **IfcBuildingStorey/Ground Floor**. Wasn't that simple? 
+
+.. image:: drag-drop-outliner-tree.png
+
+Go back to the **Scene Properties** tab and to the **IFC Project** panel and
+press **Save Project**. Save your new IFC model somewhere on your computer.
+
+.. image:: save-project.png
+
+Congratulations! You have now created your first OpenBIM model from Blender! You
+can open the IFC file in any other program, and you will see something similar
+to the image below. Three simple open source online viewers you can test with
+are `IfcPipeline <https://view.ifcopenshell.org>`__, `IFC.JS
+<https://ifcjs.github.io/web-ifc-viewer/example/index>`__, and `3DViewer
+<https://3dviewer.net/>`__.
+
+.. image:: ifc-pipeline.png
+
+Placing occurrences of an element type
+--------------------------------------
+
+TODO
+
+Changing the locations of elements
+----------------------------------
+
+TODO
+
+Modeling a simple building
+--------------------------
+
+TODO