//获取LookAt矩阵
//相机的位置 相机的看着那个位置（决定相机方向） 相机上方位置
// see:https://zhuanlan.zhihu.com/p/66384929
// Rx Ry Rz 0
// Ux Uy Uz 0
// Dx Dy Dz 0
// 0 0 0 1 相机空间是左手系
public static HMatrix GetLookAtMat(HVector camera, HVector at, HVector up)
{
HMatrix matRet = new HMatrix();
HVector CameraXAxis, CameraYAxis, CameraZAxis;
CameraZAxis = at.Sub(camera);
CameraZAxis = CameraZAxis.Normalize();
CameraYAxis = up.Normalize();
CameraXAxis = CameraZAxis.CrossProduct(CameraYAxis);
CameraXAxis = CameraXAxis.Normalize();
matRet.m[0, 0] = CameraXAxis.x;
matRet.m[1, 0] = CameraXAxis.y;
matRet.m[2, 0] = CameraXAxis.z;
matRet.m[3, 0] = -CameraXAxis.DotProduct(camera);
matRet.m[0, 1] = CameraYAxis.x;
matRet.m[1, 1] = CameraYAxis.y;
matRet.m[2, 1] = CameraYAxis.z;
matRet.m[3, 1] = -CameraYAxis.DotProduct(camera);
matRet.m[0, 2] = CameraZAxis.x;
matRet.m[1, 2] = CameraZAxis.y;
matRet.m[2, 2] = CameraZAxis.z;
matRet.m[3, 2] = -CameraZAxis.DotProduct(camera);
matRet.m[0, 3] = matRet.m[1, 3] = matRet.m[2, 3] = 0.0f;
matRet.m[3, 3] = 1.0f;
return(matRet);
}
//向量插值
public HVector InterpVec(HVector vec, float t)
{
HVector vecRet = new HVector();
vecRet.x = MathHelper.Interp(x, vec.x, t);
vecRet.y = MathHelper.Interp(y, vec.y, t);
vecRet.z = MathHelper.Interp(z, vec.z, t);
vecRet.w = 1.0f;
return(vecRet);
}
//向量减法
public HVector Sub(HVector vec)
{
HVector vecRet = new HVector();
vecRet.w = 1;
vecRet.x = x - vec.x;
vecRet.y = y - vec.y;
vecRet.z = z - vec.z;
return(vecRet);
}
//向量加法
public HVector Add(HVector vec)
{
HVector vecRet = new HVector();
vecRet.w = 1;
vecRet.x = x + vec.x;
vecRet.y = y + vec.y;
vecRet.z = z + vec.z;
return(vecRet);
}
//向量乘矩阵
public HVector MulMat(HMatrix mat)
{
HVector vec = new HVector();
float X = x, Y = y, Z = z, W = w;
vec.x = X * mat.m[0, 0] + Y * mat.m[1, 0] + Z * mat.m[2, 0] + W * mat.m[3, 0];
vec.y = X * mat.m[0, 1] + Y * mat.m[1, 1] + Z * mat.m[2, 1] + W * mat.m[3, 1];
vec.z = X * mat.m[0, 2] + Y * mat.m[1, 2] + Z * mat.m[2, 2] + W * mat.m[3, 2];
vec.w = X * mat.m[0, 3] + Y * mat.m[1, 3] + Z * mat.m[2, 3] + W * mat.m[3, 3];
return(vec);
}
//归一化 且屏幕坐标
//宽->
//高↓
public HVector HomogenizeToScreenCoord(HVector Origin)
{
int ScreenWidth = HScreenDevice.GetInstance().ScreenWidth;
int ScreenHeight = HScreenDevice.GetInstance().ScreenHeight;
float rhw = 1.0f / Origin.w;
HVector vecRet = new HVector();
vecRet.x = (Origin.x * rhw + 1.0f) * ScreenWidth * 0.5f;
vecRet.y = (1.0f - Origin.y * rhw) * ScreenHeight * 0.5f;
vecRet.z = Origin.z * rhw;
vecRet.w = 1.0f;
return(vecRet);
}
//向量归一
public HVector Normalize()
{
HVector vecRet = new HVector();
float len = Length();
if (len != 0.0f)
{
vecRet.x = x / len;
vecRet.y = y / len;
vecRet.z = z / len;
}
return(vecRet);
}
//向量叉乘 返回向量 右手螺旋决定方向
public HVector CrossProduct(HVector vec)
{
HVector vecRet = new HVector();
float m1, m2, m3;
m1 = y * vec.z - z * vec.y;
m2 = z * vec.x - x * vec.z;
m3 = x * vec.y - y * vec.x;
vecRet.x = m1;
vecRet.y = m2;
vecRet.z = m3;
vecRet.w = 1.0f;
return(vecRet);
}
public void Init()
{
int ScreenWidth = HScreenDevice.GetInstance().ScreenWidth;
int ScreenHeight = HScreenDevice.GetInstance().ScreenHeight;
ModleMat = MathHelper.GetIdentityMat();
HVector camera = new HVector(5, 0, 0, 1);
HVector at = new HVector(0, 0, 0, 1);
HVector up = new HVector(0, 1, 0, 1);
ViewMat = MathHelper.GetLookAtMat(
camera,
at,
up
);
// fov = 90度 0.5pai
ProjectionMat = MathHelper.GetPerspectiveMat(3.1415926f * 0.5f, (float)ScreenWidth / (float)ScreenHeight, 1.0f, 500.0f);
UpdateMVPMat();
}
//坐标转换到屏幕坐标
public HVector MulMVPMat(HVector Origin)
{
return(Origin.MulMat(MVPMat));
}
//向量点乘 返回是值 A x B = |A||B|Cos
public float DotProduct(HVector vec)
{
return(x * vec.x + y * vec.y + z * vec.z);
}
public a2v(HVector posPara)
{
pos = posPara;
}
