SceneKit - 用于1：1的orthographicProjection指向SceneKit位置比率 [英] SceneKit - What orthographicProjection to use for 1:1 points to SceneKit position ratio

问题描述

必须使用什么orthographicProjection才能在SceneKit中以1：1的方式制作2D应用程序SceneKit指向屏幕点/像素比率？

What orthographicProjection does one have to use to be able to make a 2D application in SceneKit with 1:1 SceneKit points to screen points/pixels ratio?

示例：
我想在屏幕上放置一些东西（200,200），我想使用带有（200,200,0）的SCNVector。我需要什么orthographicProjection？

Example: I want to position something at (200, 200) on the screen and I want to use a SCNVector with (200, 200, 0) for it. What orthographicProjection do I need for this?

推荐答案

如果你想要一个正投影，其中一个场景空间单位对应一个点在屏幕空间中，您需要一个投影，其中左侧剪切平面为零，右侧剪切平面位于屏幕的点宽度。 （同上/下，近/远无关紧要，只要你在你设置的近/远处保持物体。）

If you want an orthographic projection where a unit of scene space corresponds to a point of screen space, you need a projection where the left clipping plane is at zero and the right clipping plane is at whatever the screen's width in points is. (Ditto for top/bottom, and near/far doesn't matter so long as you keep objects within whatever near/far you set up.)

为此它可能是最容易设置自己的投影矩阵，而不是计算 orthographicScale 和相机位置对应于您需要的尺寸：

For this it's probably easiest to set up your own projection matrix, rather than working out what orthographicScale and camera position correspond to the dimensions you need:

GLKMatrix4 mat = GLKMatrix4MakeOrtho(0, self.view.bounds.size.width,
                                     0, self.view.bounds.size.height,
                                     1, 100); // z range arbitrary
cameraNode.camera.projectionTransform = SCNMatrix4FromGLKMatrix4(mat);
// still need to position the camera for its direction & z range
cameraNode.position = SCNVector3Make(0, 0, 50); 

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