对于体素艺术应用程序,目标是让用户在SceneKit场景中移动和旋转相机,然后点击以放置块 .
下面的代码允许用户通过平移来旋转相机 . 手势结束后,我们移动现有的块,使其在相机的Z轴上为-X单位(即相机前面的-X单位) .
cameraNode
是场景的观点,是 userNode
的孩子 . 当用户移动操纵杆时,我们更新 userNode.
的位置
Question: 其他SO帖子通过应用变换而不是更改旋转和位置属性来操纵相机节点 . 一种方法比另一种更好吗?
func sceneViewPannedOneFinger(sender: UIPanGestureRecognizer) {
// Get pan distance & convert to radians
let translation = sender.translationInView(sender.view!)
var xRadians = GLKMathDegreesToRadians(Float(translation.x))
var yRadians = GLKMathDegreesToRadians(Float(translation.y))
// Get x & y radians
xRadians = (xRadians / 6) + curXRadians
yRadians = (yRadians / 6) + curYRadians
// Limit yRadians to prevent rotating 360 degrees vertically
yRadians = max(Float(-M_PI_2), min(Float(M_PI_2), yRadians))
// Set rotation values to avoid Gimbal Lock
cameraNode.rotation = SCNVector4(x: 1, y: 0, z: 0, w: yRadians)
userNode.rotation = SCNVector4(x: 0, y: 1, z: 0, w: xRadians)
// Save value for next rotation
if sender.state == UIGestureRecognizerState.Ended {
curXRadians = xRadians
curYRadians = yRadians
}
// Set preview block
setPreviewBlock()
}
private func setPreviewBlock(var futurePosition: SCNVector3 = SCNVector3Zero, reach: Float = 8) -> SCNVector3 {
// Get future position
if SCNVector3EqualToVector3(futurePosition, SCNVector3Zero) {
futurePosition = userNode.position
}
// Get current position after accounting for rotations
let hAngle = Float(cameraNode.rotation.w * cameraNode.rotation.x)
let vAngle = Float(userNode.rotation.w * userNode.rotation.y)
var position = getSphericalCoords(hAngle, t: vAngle, r: reach)
position += userNode.position
// Snap position to grid
position = position.rounded()
// Ensure preview block never dips below floor
position.y = max(0, position.y)
// Return if snapped position hasn't changed
if SCNVector3EqualToVector3(position, previewBlock.position) {
return position
}
// If here, animate preview block to new position
SCNTransaction.begin()
SCNTransaction.setAnimationDuration(AnimationTime)
previewBlock.position = position
SCNTransaction.commit()
// Return position
return position
}
func getSphericalCoords(s: Float, t: Float, r: Float) -> SCNVector3 {
return SCNVector3(-(cos(s) * sin(t) * r),
sin(s) * r,
-(cos(s) * cos(t) * r))
}