希望在 ES 中进行经典的 OpenGL 鼠标拾取。我宁愿不使用第三方库，GLU 端口和 OpenGL 名称堆栈等都已淘汰。这几乎留下了逆视图变换和光线相交，对吗？
在以下帮助下，我已经走得很远了：http: //trac.bookofhook.com/bookofhook/trac.cgi/wiki/MousePicking http://eigenclass.blogspot.com/2008/10/opengl-es-picking-使用-ray-boundingbox.html
. . .但我还没到。这也让人觉得必须有更简单的方法！！
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!!!");
}
}
}
}