 notranslate nohighlight">\(\psi\)</span> with uniform density on <span class="math notranslate nohighlight">\([0,2\pi)\)</span>. Draw <span class="math notranslate nohighlight">\(\theta\)</span> uniformly from <span class="math notranslate nohighlight">\([0,2\pi)\)</span> and <span class="math notranslate nohighlight">\(\eta\)</span> from <span class="math notranslate nohighlight">\([1-r/R,1+r/R]\)</span>.  If <span class="math notranslate nohighlight">\(\eta&lt; 1 + (r/R) \cos(\theta)\)</span>, return <sp