问题
I'm trying to render a 3D model in SceneKit but it looks incorrect. For example this model (it's an SCN file with texture and you can reproduce it in your Xcode):
In Xcode Scene Editor it is rendered like this:
Transparency -> Mode -> Dual Layer
Double Sided = true
If I turn off the "Write depth" option, it will look like this: But there are also some issues because it I see only "the lowest layer" of haircut.
I think this should be possible. How to do it right?
回答1:
The reason that in your 3D model some strands of hair popped out when viewed from different angles is quite usual for SceneKit: your model has semi-transparent material that SceneKit can't render properly due to some inner engine rendering techniques (time 49:35) applied to depth buffer.
In order to deal with this problem there are two solutions:
Solution 1:
Your 3D model must have a completely opaque texture (without semi-transparent parts at all). In that case use .dualLayer property.
let scene = SCNScene(named: "art.scnassets/Hair.scn")!
let hair = scene.rootNode.childNode(withName: "MDL_OBJ", recursively: true)!
hair.geometry?.firstMaterial?.transparencyMode = SCNTransparencyMode.dualLayer
Solution 2:
Strands of hair mustn't be a mono-geometry but must be a compound geometry (consisted of several geometry layers unified in one group).
hair.geometry?.firstMaterial?.colorBufferWriteMask = SCNColorMask.all
hair.geometry?.firstMaterial?.readsFromDepthBuffer = false
hair.geometry?.firstMaterial?.writesToDepthBuffer = false
hair.geometry?.firstMaterial?.blendMode = SCNBlendMode.alpha
来源：https://stackoverflow.com/questions/57936887/render-a-3d-model-hair-with-semi-transparent-texture-in-scenekit