\[ L_o(x,\vec{w}) = L_e(x,\vec{w}) + \int_\Omega f_r(x,\vec{w}',\vec{w}) L_i(x,\vec{w}') (\vec{w}' \cdot \vec{n}) d\vec{w}' \] Note: The displayed image has transparency. You can copy the image from the menu popped up by right-clicking on it. This however may not work for some browsers and please save the image to a file in that case.