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我已经实现了 3d 光线拾取并且在准确性方面存在一些问题。在屏幕底部或中心进行选择时 - 一切正常，但在屏幕顶部的坐标似乎移动了一点。因此，当我在屏幕顶部附近选择对象时，我通常不会选择我正在点击的对象，而是选择较低的对象。

这是截图http://img838.imageshack.us/img838/9192/device20120723171612.png

我认为这个问题可能出在矩阵中，所以我是这样定义它们的：

模型视图

GLU.gluLookAt(gl, 
        camera.position.x, camera.position.y, camera.position.z,
        camera.target.x,   camera.target.y,   camera.target.z,
        camera.upAxis.x,   camera.upAxis.y,   camera.upAxis.z);

投影

horizontalCenter = 0f;
verticalCenter = 0f;
shortSideLength = 1.0f;
zNear = 1f;
zFar = 200.0f;
surfaceAspectRatio = (float) w / (float) h;
float n = shortSideLength / 2f;
gl.glFrustumf(horizontalCenter - surfaceAspectRatio*n, 
              horizontalCenter + surfaceAspectRatio*n, 
              verticalCenter - n, verticalCenter + n, zNear, zFar);

我的选择代码：

public static Point3d pickSquare(int size, float step, float tapX, float tapY, float[] modelView, float[] projection)
{

    float[] near = new float[4];
    GLU.gluUnProject(tapX, raypickingViewport[3] - tapY, 0f, modelView, 0, projection, 0, raypickingViewport, 0, near, 0);
    if (near[3] != 0)
    {
        near[0] = near[0] / near[3];
        near[1] = near[1] / near[3];
        near[2] = near[2] / near[3];
    }
    Point3d near3 = new Point3d(near[0], near[1], near[2]);

    float[] far = new float[4];
    GLU.gluUnProject(tapX, raypickingViewport[3] - tapY, 1f, modelView, 0, projection, 0, raypickingViewport, 0, far, 0);
    if (far[3] != 0)
    {
        far[0] = far[0] / far[3];
        far[1] = far[1] / far[3];
        far[2] = far[2] / far[3];
    }
    Point3d far3 = new Point3d(far[0], far[1], far[2]);

    // here I'm searching for intersection with x0z plane using equation 
    // (x-x1)/(x2-x1) = (y-y1)/(y2-y1) = (z-z1)/(z2-z1)
    // My y is 0 so I can find x and y coords.

    float intersectY = (-near3.y) / (far3.y - near3.y);
    float pickX = intersectY * (far3.x - near3.x) + near3.x;
    float pickZ = intersectY * (far3.z - near3.z) + near3.z;
    return  new Point3d(pickX, 0f, pickZ);   
}

感谢您的答复。

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1 回答 1

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问题出在android状态栏中。在 480x800 屏幕上，它的高度是 38 像素，所以我在选取方法中添加了这一行：

tapY-=38;

现在一切都很好

于 2012-07-25T13:19:24.170 回答