iphone - OpenGL ES (iPhone) 触摸拾取

Question

希望在 ES 中进行经典的 OpenGL 鼠标拾取。我不想使用第三方库，GLU 端口和 OpenGL 名称堆栈等都已退出。这几乎留下了逆 View 变换和光线相交，对吗？

在以下人员的帮助下我已经取得了很大的进展: http://trac.bookofhook.com/bookofhook/trac.cgi/wiki/MousePicking http://eigenclass.blogspot.com/2008/10/opengl-es-picking-using-ray-boundingbox.html

。 。 .但我还没到那儿。这也让人觉得必须有一种更简单的方法!!

这是一些代码:

    -(void)handleTouch:(CGPoint)point {
    GLfloat width = backingWidth;
    GLfloat height = backingHeight;
    GLfloat x = point.x;
    GLfloat y = point.y;
    GLfloat z = 0.0f;

    //viewport -> normalized dev coord -> clip
    GLfloat n[] = {
        2 * x / width - 1,
        2 * y / height,
        2 * z - 1,
        1
    };

    float fov = 45.0f * (M_PI / 180.0f);
    float near = 0.01, far = 10.0f;
    float aspect = (float)backingWidth / (float)backingHeight;
    float top = tan(fov) * near;
    //float bottom = -top;
    //float left = aspect * bottom;
    float right = aspect * top;

    //I'm a viewing volume symmetric projection matrix
    GLfloat P[] = {
        near / right, 0, 0, 0,
        0, near / top, 0, 0,
        0, 0, -(far + near) / (far - near), (-2 * far * near) / (far - near),
        0, 0, -1, 0
    };

    GLfloat Pminus1[] = {
        1/P[0], 0, 0, 0,
        0, 1/P[5], 0, 0,
        0, 0, 0, 1/P[14],
        0, 0, 1/P[11], -(P[10]/ (P[11]*P[14]))
    };

    //clip -> view
    GLfloat v[] = {
        Pminus1[0] * n[0] + Pminus1[1] * n[1] + Pminus1[2] * n[2] + Pminus1[3] * n[3],
        Pminus1[4] * n[0] + Pminus1[5] * n[1] + Pminus1[6] * n[2] + Pminus1[7] * n[3],
        Pminus1[8] * n[0] + Pminus1[9] * n[1] + Pminus1[10] * n[2] + Pminus1[11] * n[3],
        Pminus1[12] * n[0] + Pminus1[13] * n[1] + Pminus1[14] * n[2] + Pminus1[15] * n[3]
    };

    //view -> world
    GLfloat Rt[] = {
        mv[0], mv[4], mv[8],
        mv[1], mv[5], mv[9],
        mv[2], mv[6], mv[10]
    };

    GLfloat tPrime[] = {
        Rt[0] * mv[3] + Rt[1] * mv[7] + Rt[2] * mv[11],
        Rt[3] * mv[3] + Rt[4] * mv[7] + Rt[5] * mv[11],
        Rt[6] * mv[3] + Rt[7] * mv[7] + Rt[8] * mv[11]
    };

    GLfloat Mminus1[] = {
        Rt[0], Rt[1], Rt[2], -(tPrime[0]),
        Rt[3], Rt[4], Rt[5], -(tPrime[1]),
        Rt[6], Rt[7], Rt[8], -(tPrime[2]),
        0, 0, 0, 1
    };

    //point in world space
    GLfloat w[] = {
        Mminus1[0] * v[0] + Mminus1[1] * v[1] + Mminus1[2] * v[2] + Mminus1[3] * v[3],
        Mminus1[4] * v[0] + Mminus1[5] * v[1] + Mminus1[6] * v[2] + Mminus1[7] * v[3],
        Mminus1[8] * v[0] + Mminus1[9] * v[1] + Mminus1[10] * v[2] + Mminus1[11] * v[3],
        Mminus1[12] * v[0] + Mminus1[13] * v[1] + Mminus1[14] * v[2] + Mminus1[15] * v[3]
    };

    //r = a + t(w - a)
    GLfloat a[] = {0.0f, -0.1f, 0.0f};
    GLfloat wminusa[] = {w[0] - a[0], w[1] - a[1], w[2] - a[2]};

    vector[0] = a[0];
    vector[1] = a[1],
    vector[2] = a[2];
    vector[3] = w[0];
    vector[4] = w[1];
    vector[5] = -10.0f;

    //3 non-colinear points on the plane 
    GLfloat p1[] = {rect.origin.x, rect.origin.y, 0};
    GLfloat p2[] = {rect.origin.x + rect.size.width, rect.origin.y, 0};
    GLfloat p3[] = {rect.origin.x + rect.size.width, rect.origin.y + rect.size.height, 0};

    //location plane normal vector, Ax + By + Cz + D = 0
    GLfloat lp[] = {
        p1[1] * (p2[2] - p3[2]) + p2[1] * (p3[2] - p1[2]) + p3[1] * (p1[2] - p2[2]),
        p1[2] * (p2[0] - p3[0]) + p2[2] * (p3[0] - p1[0]) + p3[2] * (p1[0] - p2[0]),
        p1[0] * (p2[1] - p3[1]) + p2[0] * (p3[1] - p1[1]) + p3[0] * (p1[1] - p2[1]),
        -(p1[0] * (((p2[1] * p3[2]) - (p3[1] * p2[2]))) + p2[0] * (((p3[1] * p1[2]) - (p1[1] * p3[2]))) + p3[0] * (((p1[1] * p2[2]) - (p2[1] * p1[2]))))
    };

    GLfloat PnRd = (lp[0] * wminusa[0]) + (lp[1] * wminusa[1]) + (lp[2] * wminusa[2]);
    if(PnRd != 0) {
        GLfloat PnR0D = -((lp[0] * a[0]) + (lp[1] * a[1]) + (lp[2] * a[2]) + lp[3]);
        if(PnR0D != 0) {
            GLfloat t = PnR0D / PnRd;
            if(t >= 0) {
                GLfloat p[] = {
                    a[0] + wminusa[0] * t,
                    a[1] + wminusa[1] * t,
                    a[2] + wminusa[2] * t
                };
                if(p[0] > rect.origin.x &&
                   p[0] < rect.origin.x + rect.size.width &&
                   p[1] > rect.origin.y &&
                   p[1] < rect.origin.y + rect.size.height)
                    NSLog(@"BOOM!!!");
            }
        }
    }
}

Answer 1

这篇文章很难理解。我正在尝试使用 GLKView 在 iOS 5 上推出自己的产品；我已经研究出如何触摸检测像素 RGBA，正如我所描述的 here ，现在我正在尝试找出如何快速将场景对象的颜色更改为唯一的颜色，以配合此方法。