Decals as a fake shadow solution in SceneKit

Thank you! That's exactly what I needed.

Got this working.

WARNING - Make sure your shadow texture does not have alpha round the edges. This cost me some time. 😠

        let lightNode = SCNNode()
        let light = SCNLight()
        light.type = SCNLightTypeDirectional
       
        light.shadowMode = .Modulated
        light.castsShadow = false
        light.categoryBitMask = 0x2          //use this to restrict which objects receive the shadow
        light.orthographicScale = 10;       
       
        if let gobo = light.gobo
        {
            gobo.contents =   UIImage(named: "shadowSilhouette")
            gobo.intensity = 0.5
        }
       
        light.zFar = 100;
        light.zNear = 1.0;
        light.shadowColor =  UIColor.blackColor()
        lightNode.position = SCNVector3Make(0 , 0.0 , 0.0);
        lightNode.eulerAngles =  SCNVector3(Scalar.halfPi, 0 , 0)      //point the shadow downwards 
        lightNode.light = light
        self._node.addChildNode(lightNode)