Index: src/sas/sasgui/perspectives/fitting/media/sm_help.rst
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--- src/sas/sasgui/perspectives/fitting/media/sm_help.rst	(revision d85c194ea2f78cb2b9b3de9c969e1b8ebea6b6d2)
+++ src/sas/sasgui/perspectives/fitting/media/sm_help.rst	(revision d85c194ea2f78cb2b9b3de9c969e1b8ebea6b6d2)
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+.. sm_help.rst
+
+.. This is a port of the original SasView html help file to ReSTructured text
+.. by S King, ISIS, during SasView CodeCamp-III in Feb 2015.
+
+.. |beta| unicode:: U+03B2
+.. |gamma| unicode:: U+03B3
+.. |mu| unicode:: U+03BC
+.. |sigma| unicode:: U+03C3
+.. |phi| unicode:: U+03C6
+.. |theta| unicode:: U+03B8
+.. |chi| unicode:: U+03C7
+.. |bigdelta| unicode:: U+0394
+
+.. |inlineimage004| image:: sm_image004.gif
+.. |inlineimage005| image:: sm_image005.gif
+.. |inlineimage008| image:: sm_image008.gif
+.. |inlineimage009| image:: sm_image009.gif
+.. |inlineimage010| image:: sm_image010.gif
+.. |inlineimage011| image:: sm_image011.gif
+.. |inlineimage012| image:: sm_image012.gif
+.. |inlineimage018| image:: sm_image018.gif
+.. |inlineimage019| image:: sm_image019.gif
+
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+Smearing Functions
+==================
+
+Sometimes it will be necessary to correct reduced experimental data for the
+physical effects of the instrumental geometry in use. This process is called
+*desmearing*. However, calculated/simulated data - which by definition will be
+perfect/exact - can be *smeared* to make it more representative of what might
+actually be measured experimentally.
+
+SasView provides the following three smearing algorithms:
+
+*  *Slit Smearing*
+*  *Pinhole Smearing*
+*  *2D Smearing*
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+Slit Smearing
+-------------
+
+**This type of smearing is normally only encountered with data from X-ray Kratky**
+**cameras or X-ray/neutron Bonse-Hart USAXS/USANS instruments.**
+
+The slit-smeared scattering intensity is defined by
+
+.. image:: sm_image002.gif
+
+where *Norm* is given by
+
+.. image:: sm_image003.gif
+
+**[Equation 1]**
+
+The functions |inlineimage004| and |inlineimage005|
+refer to the slit width weighting function and the slit height weighting 
+determined at the given *q* point, respectively. It is assumed that the weighting
+function is described by a rectangular function, such that
+
+.. image:: sm_image006.gif
+
+**[Equation 2]**
+
+and
+
+.. image:: sm_image007.gif
+
+**[Equation 3]**
+
+so that |inlineimage008| |inlineimage009| for |inlineimage010| and *u*\ .
+
+Here |inlineimage011| and |inlineimage012| stand for
+the slit height (FWHM/2) and the slit width (FWHM/2) in *q* space.
+
+This simplifies the integral in Equation 1 to
+
+.. image:: sm_image013.gif
+
+**[Equation 4]**
+
+which may be solved numerically, depending on the nature of |inlineimage011| and |inlineimage012| .
+
+Solution 1
+^^^^^^^^^^
+
+**For** |inlineimage012| **= 0 and** |inlineimage011| **= constant.**
+
+.. image:: sm_image016.gif
+
+For discrete *q* values, at the *q* values of the data points and at the *q*
+values extended up to *q*\ :sub:`N`\ = *q*\ :sub:`i` + |inlineimage011| the smeared
+intensity can be approximately calculated as
+
+.. image:: sm_image017.gif
+
+**[Equation 5]**
+
+where |inlineimage018| = 0 for *I*\ :sub:`s` when *j* < *i* or *j* > *N-1*.
+
+Solution 2
+^^^^^^^^^^
+
+**For** |inlineimage012| **= constant and** |inlineimage011| **= 0.**
+
+Similar to Case 1
+
+|inlineimage019| for *q*\ :sub:`p` = *q*\ :sub:`i` - |inlineimage012| and *q*\ :sub:`N` = *q*\ :sub:`i` + |inlineimage012|
+
+**[Equation 6]**
+
+where |inlineimage018| = 0 for *I*\ :sub:`s` when *j* < *p* or *j* > *N-1*.
+
+Solution 3
+^^^^^^^^^^
+
+**For** |inlineimage011| **= constant and** |inlineimage011| **= constant.**
+
+In this case, the best way is to perform the integration of Equation 1
+numerically for both slit height and slit width. However, the numerical
+integration is imperfect unless a large number of iterations, say, at
+least 10000 by 10000 for each element of the matrix *W*, is performed.
+This is usually too slow for routine use.
+
+An alternative approach is used in SasView which assumes
+slit width << slit height. This method combines Solution 1 with the
+numerical integration for the slit width. Then
+
+.. image:: sm_image020.gif
+
+**[Equation 7]**
+
+for *q*\ :sub:`p` = *q*\ :sub:`i` - |inlineimage012| and *q*\ :sub:`N` = *q*\ :sub:`i` + |inlineimage012|
+
+where |inlineimage018| = 0 for *I*\ :sub:`s` when *j* < *p* or *j* > *N-1*.
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+Pinhole Smearing
+----------------
+
+**This is the type of smearing normally encountered with data from synchrotron**
+**SAXS cameras and SANS instruments.**
+
+The pinhole smearing computation is performed in a similar fashion to the slit-
+smeared case above except that the weight function used is a Gaussian. Thus
+Equation 6 becomes
+
+.. image:: sm_image021.gif
+
+**[Equation 8]**
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+2D Smearing
+-----------
+
+The 2D smearing computation is performed in a similar fashion to the 1D pinhole
+smearing above except that the weight function used is a 2D elliptical Gaussian.
+Thus
+
+.. image:: sm_image022.gif
+
+**[Equation 9]**
+
+In Equation 9, *x*\ :sub:`0` = *q* cos(|theta|), *y*\ :sub:`0` = *q* sin(|theta|), and
+the primed axes, are all in the coordinate rotated by an angle |theta| about
+the z-axis (see the figure below) so that *x'*\ :sub:`0` = *x*\ :sub:`0` cos(|theta|) +
+*y*\ :sub:`0` sin(|theta|) and *y'*\ :sub:`0` = -*x*\ :sub:`0` sin(|theta|) +
+*y*\ :sub:`0` cos(|theta|). Note that the rotation angle is zero for a x-y symmetric
+elliptical Gaussian distribution. The *A* is a normalization factor.
+
+.. image:: sm_image023.gif
+
+Now we consider a numerical integration where each of the bins in |theta| and *R* are
+*evenly* (this is to simplify the equation below) distributed by |bigdelta|\ |theta|
+and |bigdelta|\ R, respectively, and it is further assumed that *I(x',y')* is constant
+within the bins. Then
+
+.. image:: sm_image024.gif
+
+**[Equation 10]**
+
+Since the weighting factor on each of the bins is known, it is convenient to
+transform *x'-y'* back to *x-y* coordinates (by rotating it by -|theta| around the
+*z* axis).
+
+Then, for a polar symmetric smear
+
+.. image:: sm_image025.gif
+
+**[Equation 11]**
+
+where
+
+.. image:: sm_image026.gif
+
+while for a *x-y* symmetric smear
+
+.. image:: sm_image027.gif
+
+**[Equation 12]**
+
+where
+
+.. image:: sm_image028.gif
+
+The current version of the SasView uses Equation 11 for 2D smearing, assuming
+that all the Gaussian weighting functions are aligned in the polar coordinate.
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+Weighting & Normalization
+-------------------------
+
+In all the cases above, the weighting matrix *W* is calculated on the first call
+to a smearing function, and includes ~60 *q* values (finely and evenly binned)
+below (>0) and above the *q* range of data in order to smear all data points for
+a given model and slit/pinhole size. The *Norm*  factor is found numerically with the
+weighting matrix and applied on the computation of *I*\ :sub:`s`.
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+.. note::  This help document was last changed by Steve King, 01May2015
