Changeset 9802ab3 in sasmodels for sasmodels/models/cylinder.py

Timestamp:

Apr 10, 2017 11:56:55 AM (7 years ago)

Author:

richardh

Branches:

master, core_shell_microgels, costrafo411, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests

Children:

69e1afc

Parents:

dedcf34

Message:

changes to docs, anticipating new orientation angle integrals

File:

• sasmodels/models/cylinder.py (modified) (2 diffs)

sasmodels/models/cylinder.py

@@ -61 +61 @@
 .. _cylinder-angle-definition:
 
-.. figure:: img/cylinder_angle_definition.jpg
+.. figure:: img/cylinder_angle_definition.png
 
-    Definition of the angles for oriented cylinders.
+    Definition of the $\theta$ and $\phi$ orientation angles for a cylinder relative 
+    to the beam line coordinates, plus an indication of their orientation distributions 
+    which are described as rotations about each of the perpendicular axes $\delta_1$ and $\delta_2$ 
+    in the frame of the cylinder itself, which when $\theta = \phi = 0$ are parallel to the $Y$ and $X$ axes.
 
 .. figure:: img/cylinder_angle_projection.png
@@ -69 +72 @@
     Examples for oriented cylinders.
 
-The $\theta$ and $\phi$ parameters only appear in the model when fitting 2d data.
+The $\theta$ and $\phi$ parameters to orient the cylinder only appear in the model when fitting 2d data. 
+On introducing "Orientational Distribution" in the angles, "distribution of theta" and "distribution of phi" parameters will
+appear. These are actually rotations about the axes $\delta_1$ and $\delta_2$ of the cylinder, which when $\theta = \phi = 0$ are parallel 
+to the $Y$ and $X$ axes of the instrument respectively. Some experimentation may be required to understand the 2d patterns fully.
+(Earlier implementations had numerical integration issues in some circumstances when orientation distributions passed through 90 degrees, such 
+situations, with very broad distributions, should still be approached with care.) 
 
 Validation