android - OpenGL ES 2.0 中的光线拾取

Question

我正在尝试在 OpenGL ES 2.0 中实现光线拾取以确定是否已单击对象。到目前为止，我只是想检查是否按下了特定的三角形。我用这个网站作为动力 http://android-raypick.blogspot.ca/2012/04/first-i-want-to-state-this-is-my-first.html

这是我目前所拥有的:

public void onClick(float x, float y)
{
    float[] temp = new float[4];
    float[] temp2 = new float[4];
    System.out.println("X coordinate: " + x);
    System.out.println("Y coordinate: " + y);
    float[] pos = new float[4];

    y = (float) viewport[3] - y;

    int res = GLU.gluUnProject(x, y, 1.0f, 
            mMVPMatrix, 0,
            mProjectionMatrix, 0,
            viewport, 0, 
            temp, 0);

    Matrix.multiplyMV(temp2, 0, mMVPMatrix, 0, temp, 0);
    float[] nearCoOrds = new float[3];

    if(res == GLES20.GL_TRUE)
    {
        nearCoOrds[0] = temp2[0] / temp2[3];
        nearCoOrds[1] = temp2[1] / temp2[3];
        nearCoOrds[2] = temp2[2] / temp2[3];
        System.out.println("Near0: " + nearCoOrds[0]);
        System.out.println("Near1: " + nearCoOrds[1]);
        System.out.println("Near2: " + nearCoOrds[2]);
    }

    res = GLU.gluUnProject(x, y, 0,
            mMVPMatrix, 0,
            mProjectionMatrix, 0,
            viewport, 0,
            temp, 0);

    Matrix.multiplyMV(temp2,0,mMVPMatrix, 0, temp, 0);
    float[] farCoOrds = new float[3];

    if(res == GLES20.GL_TRUE)
    {
        farCoOrds[0] = temp2[0] / temp2[3];
        farCoOrds[1] = temp2[1] / temp2[3];
        farCoOrds[2] = temp2[2] / temp2[3];
        System.out.println("Far0: " + farCoOrds[0]);
        System.out.println("Far1: " + farCoOrds[1]);
        System.out.println("Far2: " + farCoOrds[2]);
    }

    float[] coords = new float[3];

    coords[0] = farCoOrds[0]-nearCoOrds[0];
    coords[1] = farCoOrds[1]-nearCoOrds[1];
    coords[2] = farCoOrds[2]-nearCoOrds[2];

    System.out.println("REAL COORDS 0: " + coords[0]);
    System.out.println("REAL COORDS 1: " + coords[1]);
    System.out.println("REAL COORDS 2: " + coords[2]);

}

x 和y float 是手指按下屏幕位置的 x 和 y 坐标。 onClick 函数从 MainActivity 调用。

在

 GLU.gluUnProject(x, y, 1.0f, 
            mMVPMatrix, 0,
            mProjectionMatrix, 0,
            viewport, 0, 
            temp, 0);

mMVPMatrix 是模型 View 矩阵。 mProjectionMatrix 是投影矩阵，viewport 的值为 {0,0,screenhwidth,screenheight}。

我得到的输出示例是(触摸屏幕中间):

REAL COORDS 0: -0.21542415
REAL COORDS 1: 0.31117013
REAL COORDS 2: 9.000003

我的问题/主题是我不知道我是否在正确的轨道上？我的想法是正确的还是我似乎误解了什么？或者有什么其他方法可以实现对三角形的触摸检测吗？

感谢您的帮助或指导!

Answer 1

Android 有一个优秀的 OpenGL 框架，叫做 Rajawali .它支持对象拾取，the sample code看起来很简单，你应该试试。