In Shaderlight 2016 the old skylight portal placement tool has been replaced by a new version that allows you to pick any pre-existing face as a template for the portal. This makes it possible to create portals of any shape that you can create using any of SketchUp’s built-in drawing tools, or indeed with many third-party extensions.
To create a skylight portal, activate Shaderlight’s light tool and select ‘Skylight Portal’ from the pop-up menu.
Then simply click on the face you wish to use as a template. The new portal will be created precisely on top of the clicked face.
By default, the portal will face the same direction as the face you select. It is important that portals face in the direction that sun- and skylight will be travelling in – that is, the front face should be on the ‘inside’ of the enclosed space. The placement tool draws an arrow to indicate the direction of light flow and should point from the outside to the inside when you place the portal. The face under the cursor is also highlighted with a different shade of blue depending on the direction the portal will face – the ‘inside’ is a bright blue and the ‘outside’ is a dull blue.
If you hold down the shift key while placing the portal, the direction of the portal will be reversed. This is helpful if the template face doesn’t already point in the correct direction.
You can also hold down the control (Windows) or option (OS X) key to erase the template face when creating the portal. Use this when selecting a temporary template face to specify the opening that the portal should cover but that doesn’t otherwise represent any geometry in your model. The standard behaviour is used when the template is a transparent or translucent object (such as a pane of glass) that should remain part of the model. Note that if the template face has an opaque material applied to it and you don’t erase it the portal will be ineffective, because the opaque face will still be blocking the light from passing through.