message: fix typo and improve language in important sampling doc
diff: @@ -3463,7 +3463,8 @@ $$\begin{equation}\label{iblSampling}
  Unfortunately, we would need too many samples to evaluate this integral. A technique commonly used
  is to choose samples that are more "important" more often, this is called _importance sampling_.
  -In our case we'll use $D_{ggx}\left< \NoH \right>$ as probability density function (PDF) for our samples.
  +In our case we'll use the distribution of micro-facets normals, $D_{ggx}$, as the distribution of
  +important samples.
  The evaluation of $ \Lout(n,v,\Theta) $ with importance sampling is presented in equation $\ref{annexIblImportanceSampling}$.
  @@ -3472,11 +3473,10 @@ $$\begin{equation}\label{annexIblImportanceSampling}
  \end{equation}$$
  In equation $\ref{annexIblImportanceSampling}$, $p$ is the probability density function (PDF) of the
  -samples, and $l_i$ represents the _important direction samples_. These samples depend on $h_i$, $v$ and $\alpha$.
  +distribution of _important direction samples_ $l_i$. These samples depend on $h_i$, $v$ and $\alpha$.
  The definition of the PDF is shown in equation $\ref{iblPDF}$.
  -$h_i$ is given by the PDF we chose, here $D_{ggx}\left< \NoH \right>$ from a uniform distribution,
  -see section [Choosing important directions] for more details.
  +$h_i$ is given by the distribution we chose, see section [Choosing important directions] for more details.
  The _important direction samples_ $l_i$ are calculated as the reflection of $v$ around $h_i$, and therefore
  **do not** have the same PDF as $h_i$. The PDF of a transformed distribution is given by:
  