增强现实演示
我正在尝试构建一个增强现实演示，例如这个 iPhone 应用程序： http://www.acrossair.com/acrossair_app_augmented_reality_nearesttube_london_for_iPhone_3GS.htm
但是我的几何/数学有点如今生锈了。
这就是我所知道的：
如果我的 Android 手机处于横向模式（主页按钮位于左侧），我的 z 轴指向我正在看的方向。
从我手机的传感器我知道我的 z 轴与北轴的角度是多少，我们称之为角度 theta。
如果我有一个从当前位置到我想要在屏幕上显示的点的向量，我可以计算该向量与 z 轴的角度。我们将这个角度称为 alpha。
因此，根据 alpha 角度，我可以感知该点的位置，并且可以在屏幕上显示它（如最近的地铁应用程序）。
这是一个简单演示的基本理论（当然它与App没什么不同，但这是第一步）。
有人能给我一些关于这件事的线索吗？
[更新]
我发现这个非常有趣的示例，但是我需要在 xx 和 yy 轴上都有运动。有什么提示吗？
I'm trying to build an Augmented Reality Demonstration, like this iPhone App:
http://www.acrossair.com/acrossair_app_augmented_reality_nearesttube_london_for_iPhone_3GS.htm
However my geometry/math is a bit rusty nowadays.
This is what I know:
If i have my Android phone on the landscape mode (with the home button on the left), my z axis points to the direction I'm looking.
From the sensors of my phone i know what is the angle my z axis has with the North axis, let's call this angle theta.
If I have a vector from my current position to the point I want to show in my screen, i can calculate the angle this vector does with my z axis. Let's call this angle alpha.
So, based on the alpha angle I have a perception of where the point is, and I'm able to show it in the screen (like the Nearest Tube App).
This is the basic theory of a simple demonstration (of course it's nothing like the App, but it's the first step).
Can someone give me some lights on this matter?
[Update]
I've found this very interesting example, however I need to have the movement on both xx and yy axis. Any hints?
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基础知识很简单。您需要您的位置和您的命运之间的角度（反正切）以及航向（来自手机中的数字罗盘）。请参阅此答案：增强现实运动下面有一些您可以使用的objective-c代码如果您来自java，可以阅读。
The basics are easy. You need the angle between your location and your destiny (arctangent), and the heading (from the digital compass in your phone). See this answer: Augmented Reality movement There is some objective-c code down there that you can read if you come from java.
您想要的是 3d 空间填充曲线，例如希尔伯特曲线。这是一个超过 3 坐标的空间索引。它相当于八叉树。您想要将对象存储在该八叉树中，并对您用 iPhone 记录的坐标（可能是屏幕中心的固定坐标）进行深度搜索。八叉树在八个方向上连续细分空间，3d 空间填充曲线是穿过空间的哈密尔顿路径，类似于分形，但它与八叉树的区域明显不同。我使用 2d-hilbert-curve 来加速地理空间数据库中的搜索。也许你想先从这个开始？
What you want is a 3d-Space-Filling-Curve for example a hilbert-curve. That is a spatial index over 3 ccordinate. It is comparable to a octree. You want to store the object in that octree and do a depth-firat search on the coordinate you have recorded with your iphone as fixed coordinate probably the center of the screen. A octree subdivde the space continously in eigth directions and a 3d-Space-Filling-Curve is an hamiltonian path through the space which is like a fracta but it is clearly distinctable from the region of the octree. I use 2d-hilbert-curve to speed search in geospatial databases. Maybe you want to start with this first?