stubbing out docs

README.md

@@ -29,6 +29,7 @@ loaded in yt.  It is written to provide both scripting and interactive access.
     * Block and grid outlines
 * Support for sub-selections of data via the yt data selection interface
 * Integration with the [ipywidgets](https://ipywidgets.readthedocs.org/) ``Image`` widget.
+* Direct volume rendering of block-AMR data in spherical coordinates.
 
 ## Examples
 

docs/coordinate_systems.rst

@@ -0,0 +1,55 @@
+.. highlight:: shell
+
+================================
+Non-Cartesian Coordinate Systems
+================================
+
+Initial support for volume rendering of data defined in 3D non-cartesian coordinate systems
+was added in yt_idv 0.5.0 for block-AMR data in spherical coordinates. While not all
+rendering methods and annotations are supported for spherical coordinates, yt_idv can
+directly calculate maximum intensity projections, integrative projections and projection with custom
+transfer functions without any pre-interpolation or re-gridding (with some caveats).
+
+PUT A NICE SCREEN SHOT HERE.
+
+---------------------------------------------------
+Volume Rendering of Data in a Spherical Coordinates
+---------------------------------------------------
+
+Overview
+
+#. pre-calculation of cartesian bounding boxes of the amr blocks, accelerated with cython.
+#. load block data as textures in normalized native coordinates (just like cartesian)
+#. pass down cartesian boudning boxes and spherical bounding boxes of blocks as vertex attributes
+#. standard slab test with the cartesian bounding boxes for ray-element intersections
+#. step along ray, calculate spherical coordinates (in the shader!), evalulate texture (discarding points outside the actual speherical volume element).
+
+
+Mention: Pre-processor switches in order to re-use carteisan shaders efficiently.
+
+The main limitation in this approach is in stepping along the ray: intersection with the
+ cartesian bounding box of a spherical element does not gaurentee intersection with the enclosed
+spherical elemnt. So a fairly large number of sample points along the ray must be used, increasing
+the computational cost to achieve the same fidelity as rendering data that is natively in
+cartesian coordinates.
+
+----------------------------
+Notes on further development
+----------------------------
+
+Further contributions are welcome for adding support for the remaining 3d non-cartesian coordinate systems
+that yt supports that are not yet supported here (3d cylindrical, 3d geographic) as well as for adding
+support for non-cartesian coordinate systems in additional yt_idv components.
+
+****************************************
+Supporting additional coordinate systems
+****************************************
+
+Describe coordinate_utilities.pyx (and .pxd), how to add a new coordinate system.
+
+***************************************
+Supporting additional rendering methods
+***************************************
+
+Adding additional coordiante system conversions to shaders (with pre-processor
+directives).

docs/index.rst

@@ -9,6 +9,7 @@ Welcome to yt_idv's documentation!
    installation
    usage
    scene
+   coordinate_systems
    examples
    modules
    contributing