What does IShadowVolumeSceneNode do?

[dart_theg]

I think I'm misusing this node. Does it make it so nodes cast a shadow? Or gives them a shadow?

[Noiecity]

will generally cause it to produce a shadow cast on the surface of another model or on top of the same model, the other shadows are achieved with gouraud shading and dynamic lighting by default

[CuteAlien]

First it creates a shadow volume. That are polygons which extends the edges of your models away from the lights (one shadow volume per light which is close enough). That works best if the model is "closed" aka - when put water in the model it will stay inside. Which edges are extended depens on setOptimization setting in IShadowVolumeSceneNode - by default it tries to find a silhouette and only extend those. But for models where this isn't working it's also possible to extend every triangle (you'll see if it works or fails - when it fails you get long black lines). Usually the better option is to fix the model, but you might not always be able to do that.

Then in the second step the node renders those shadow volumes to the stencil buffer in a bit specific way. There's 2 algorithms implemented zPass and zFail - you can experiment with both of them. Each has it's areas where it shines and fails I think. For reasons I don't remember it's a bit of a counting thing how many shadow volume polygons are passed at each point and the result has to be odd or even or something like that for a shadow to be drawn. Pretty sure you can find some better info on the web (I learned it once a few years ago, but would have to read up on it again). (edit: Odd number of shadow polygons passed should mean a point is inside the shadow - which will mess up if the camera or light starts inside an object, so that should be avoided)

Then the node tells the scenemanager - I've got stuff in the stencil buffer (SceneManager->requestDrawShadowPassStencilShadow). If that's so the SceneManager will call drawStencilShadow in it's shadow pass (after solids, before transparent stuff). And that's basically adding the shadow color to all the places marked in the stencil buffer.

[dart_theg]

Great explanation! Thank you