Portal checkbox in principled shader to turn any mesh into a portal
Often you need to use portals on windows to speed up rendering. This means you have to physically place a light outside the window, which can sometimes be extremely time consuming.
It would be better if you could just check a 'Portal' checkbox in the principled shader, which would effectively make the geometry act as a portal.
So in the case of glass for example, you'd check the checkbox, the glass would still look like glass, but the mesh would be used to light the scene.
5 Comments
I don't think that makes sense. Positioning light portals is a pretty specific process, and it won't work to simply use the window geometry... If I remember correctly you're supposed to make the portal slightly bigger than the hole or window. Moreover, portals don't emit light, and they are two-dimensional. How would the material know how to flatten the mesh? Or would it create a portal for each triangle ( like material emission, which creates a light for each triangle)?
Portals merely tell light where to (try) go! So you use an area light set to "portal" for this. I think maybe for UI consistency light portals should be a Light Probe object instead.
* @Josephbburg * in other renderers that have the functionality i'm describing, the normal of the geometry is responsible when using a portal shader rather than a portal object.
Fstorm is a good example, and I think Corona also has this functionality.
It just means you can make hundreds of windows into portals by clicking one checkbox in the glass material assigned to all of them. Very handy, and much more accurate because the shape is correct (no bright white areas around external brickwork etc, which is important if you have an animated camera shot that moves between interior and exterior)
Oh, I see. Cool. Maybe it is a good idea! That sounds really handy by itself.
You can do this with the light path node, to separate the emission and the material. Is it that you want ?
* @Kdaf * As I understand it the portal provides a little more functionality that a light. It actually gets the lighting information from the HDRI, and presumably presents a different result to incoming rays based on angle.