SceneKit shadows on wall

问题

I have a cube, a wall and two lightNodes in my SceneKit application and I would like to make the cube throw a shadow onto the wall.

My lightNodes are here:

    let lightNode = SCNNode()
    lightNode.light = SCNLight()
    lightNode.light!.type = SCNLightTypeSpot
    lightNode.position = SCNVector3(x: 0, y: 0, z: 15)
    lightNode.castsShadow = true
    scene.rootNode.addChildNode(lightNode)

    // create and add an ambient light to the scene
    let ambientLightNode = SCNNode()
    ambientLightNode.light = SCNLight()
    ambientLightNode.light!.type = SCNLightTypeAmbient
    ambientLightNode.light!.color = UIColor.darkGrayColor()
    ambientLightNode.castsShadow = true
    scene.rootNode.addChildNode(ambientLightNode)

This is my wall:

    var wall = SCNNode(geometry: SCNBox(width: 400, height: 100, length: 4, chamferRadius: 0))
    wall.geometry?.firstMaterial!.emission.contents = UIColor.lightGrayColor()
    wall.geometry?.firstMaterial!.doubleSided = false
    wall.castsShadow = true
    wall.position = SCNVector3Make(0, 0, -5)
    wall.physicsBody = SCNPhysicsBody.staticBody()
    scene.rootNode.addChildNode(wall)

As you can see all of the nodes (including the cube) have the property to cast shadow, since it is true.

How does it come that there is no shadow on the wall?

回答1:

same issue as here? You have to set castsShadow on the light (instead of on the node that holds the light).

Also note that omnidirectional and ambient lights can not cast shadows. Only directional and spot lights can.

回答2:

I'm not sure why this is the case, but I was having a similar issue and found that setting the light's shadowMode to SCNShadowModeDeferred fixed it.

来源：https://stackoverflow.com/questions/29827311/scenekit-shadows-on-wall