public ViewTransform(RtPoint from, RtPoint to, RtVector up)
{
Up = up;
To = to;
From = from;
Forward = (To - From).Normalize();
var upNormalized = Up.Normalize();
Left = Forward.Cross(upNormalized);
var trueUp = Left.Cross(Forward);
var orientation = RtMatrix.Identity;
orientation.M11 = Left.X;
orientation.M12 = Left.Y;
orientation.M13 = Left.Z;
orientation.M21 = trueUp.X;
orientation.M22 = trueUp.Y;
orientation.M23 = trueUp.Z;
orientation.M31 = -Forward.X;
orientation.M32 = -Forward.Y;
orientation.M33 = -Forward.Z;
var translation = RtMatrix.Identity;
translation.M14 = -from.X;
translation.M24 = -from.Y;
translation.M34 = -from.Z;
Matrix = orientation * translation;
}
Matrix LookAt(Vector3 up)
{
Vector3 right = Forward.Cross(up);
right.Normalize( );
Vector3 recalcUp = right.Cross(Forward);
recalcUp.Normalize( );
return
(Matrix.LookAtLH(Position, Target, recalcUp));
}
public void Update(float delaMs)
{
// view
Vector3 t = this.Translate;
if (target.HasValue)
{
// look at
View = Matrix4x4.GenLookAt(t, target.Value, up);
// 将view matrix的前三行三列(3x3)，每一行对应：Left, Up, Forward三轴，来求得各个轴的当前角度
// 因为LookAt实际上是求了view的反向变换：逆矩阵，下面的矩阵的转置为原来的变换矩阵
/*
* view 是右手坐标系
* lx,ly,lz是x，左边为正，所以命名为：Left:l
* ux,uy,uz是y，上边为正，所以命名为：Up:u
* fx,fy,fz是z，向前为正，所以命名为：Forward:f
* http://www.songho.ca/opengl/gl_camera.html#lookat
|lx|ly|lz|0 | |1 |0 |0 |-tx| |lx|ly|lz|lx*(-tx)+ly*(-ty)+lz*(-tz)|
|ux|uy|uz|0 |* |0 |1 |0 |-ty|= |ux|uy|uz|ux*(-tx)+uy*(-ty)+uz*(-tz)|
|fx|fy|fz|0 | |0 |0 |1 |-tz| |fx|fy|fz|fx*(-tx)+fy*(-ty)+fz*(-tz)|
|0 | 0| 0|1 | |0 |0 |0 |1 | |0 |0 |0 |1 |
* */
// 后面再实现
}
else
{
t = -t;
var r = R_Before_T;
// translate
View = Matrix4x4.GenTranslateMat(t.x, t.y, t.z) * Matrix4x4.GenEulerMat(r.x, r.y, r.z);
// rotate
View = Matrix4x4.GenEulerMat(Euler.x, Euler.y, Euler.z).MulMat(View);
}
var matV = Matrix4x4.GenEulerMat(-Euler.x, -Euler.y, -Euler.z);
Forward = matV * forward;
Right = matV * right;
Up = Forward.Cross(Right);
// proj
if (isOrtho)
{
// orthogonal
Proj = Matrix4x4.GenOrthoFrustum(aspect, size, near, far);
}
else
{
// perspective
Proj = Matrix4x4.GenFrustum(fov, aspect, near, far);
}
}