目录
一,四元数相关概念
四元数
欧拉角
常用四元数相关函数
相互转换
二,案例
案例:沿面中心翻转
案例:路径导弹
案例:RBD刚体还原过渡
一,四元数相关概念
四元数
- 在vex内四元数为((x,y,z),w);
//VEX内获得四元数 vector4 quaternion(matrix3 rotations) //仅应用矩阵的旋转信息 vector4 quaternion(float angle, vector axis) vector4 quaternion(vector angleaxis) //方向为旋转轴,大小为旋转角度vector4 eulertoquaternion(vector rotations, int order)
注,数学运算,如绕某向量 K=(, , ) 旋转,则四元数为:
- (x,y,z) = (, , ) *
- w =
- 且满足条件:+++=1
欧拉角
由环绕三个轴旋转的角度组成的矢量表示
- 绕著x轴的旋转(Roll),绕著交点线的旋转(Pitch),绕著z轴的旋转(Yaw);
- 任何旋转矩阵都是由三个基本旋转矩阵复合而成的;
- 不同旋转顺序,结果不同,默认旋转顺序XYZ;
//VEX内获得欧拉角 vector quaterniontoeuler(vector4 orient, int order)
注,可使用Transform节点应用欧拉角;
常用四元数相关函数
dihedral()
quaternion()
qrotate()
qmultiply()
qinvert()
qdistance()
qconvert()
eulertoquaternion()
quaterniontoeuler()
slerp()
相互转换
//矩阵转四元数 matrix m = detail(1, 'xform'); vector4 q = quaternion(matrix3(m));
//四元数转矩阵 vector4 q = quaternion(ch('ang'), chv('axis')); matrix3 m = qconvert(q);
//欧拉角转矩阵或四元数 v@euler_angle = degrees(chv('ang')); vector4 q = eulertoquaternion(@euler_angle); matrix3 m = qconvert(q);
//四元数或矩阵,获取欧拉角 matrix m = detail(1, 'xform'); vector4 q = quaternion(matrix3(m)); v@euler_angle = degrees(quaterniontoeuler(q, 0));
二,案例
- 设置旋转,dihedral,quaternion,orient(可用于copy);
- 合并旋转,qmultiply
- 应用旋转,qrotate
案例:沿面中心翻转
//point层级,并获取所属面的其他点
int pts[] = primpoints(0, @primnum);
vector pos0 = point(0, 'P', pts[0]);
vector pos1 = point(0, 'P', pts[1]);
vector pos2 = point(0, 'P', pts[2]);
vector pos3 = point(0, 'P', pts[3]);
//方法一,先归到中心点旋转,在还原 vector center = (pos0+pos1+pos2+pos3)/4; vector axis = normalize(pos1-pos0);@P -= center;float ang = @Time; vector4 q = quaternion(ang, axis); @P = qrotate(q,@P);@P += center;
//方法二,使用maketransform vector pivot = (pos0+pos1+pos2+pos3)/4; vector axis = normalize(pos1-pos0);//直接绕axis旋转 float ang = @Time; vector4 q_r = quaternion(ang, axis); vector r = degrees(quaterniontoeuler(q_r, 0));@P *= maketransform(0,0,0,r,1,pivot,0);//绕x轴旋转,中心点旋转偏移到axis float ang = @Time; vector dir = set(1,0,0); vector r = dir * degrees(ang); vector4 q_pr = dihedral(dir, axis); vector pr = degrees(quaterniontoeuler(q_pr, 0));@P *= maketransform(0,0,0,r,1,pivot,pr);
//方法三,使用函数instance vector pivot = (pos0+pos1+pos2+pos3)/4; vector axis = normalize(pos1-pos0);float ang = @Time; vector4 orient = quaternion(ang, axis); @P *= instance(pivot,0,1,0,orient,pivot);
//方法二,手搓矩阵(即将本身或局部坐标系恢复到世界坐标系,旋转后,在还原到原坐标系) vector center = (pos0+pos1+pos2+pos3)/4; vector xaxis = normalize(pos1-pos0); vector yaxis = normalize(prim(0,'N',@primnum)); vector zaxis = normalize(cross(xaxis, yaxis));matrix m = set(xaxis, yaxis, zaxis, center); m.xa = m.ya = m.za = 0; @P *= invert(m);float ang = @Time; vector4 q = quaternion(ang, set(1,0,0)); @P = qrotate(q, @P);@P *= m;
案例:路径导弹
//方法一
vector tangentu = -primuv(1, 'tangentu', 0, ch('u'));
vector tangentv = primuv(1, 'tangentv', 0, ch('u'));
vector pos = primuv(1, 'P', 0, ch('u'));vector4 rot1 = dihedral(set(1,0,0), tangentu);
vector4 rot2 = quaternion(@Time*10, set(1,0,0));
vector4 rot = qmultiply(rot1, rot2);//如不是pack物体
@P = qrotate(rot, @P) + pos;//如是pack物体,使用以下代码
@P = pos;
matrix3 m = qconvert(rot);
setprimintrinsic(0, "transform", 0, m);
//方法二
vector x_axis = -primuv(1, 'tangentu', 0, ch('u'));
vector y_axis = primuv(1, 'tangentv', 0, ch('u'));
vector z_axis = cross(x_axis, y_axis);
vector pos = primuv(1, 'P', 0, ch('u'));matrix m = set(normalize(x_axis), normalize(y_axis), normalize(z_axis), pos);
vector4 q = quaternion(@Time*10, set(1,0,0));@P = qrotate(q, @P);
@P *= m;
案例:RBD刚体还原过渡
- RBD刚体的中心和质心(rest信息)的区别;
注,pack对象intrinsic属性
- transform,存储旋转信息,使用setprimintrinsic函数设置;
- packedfulltransform,存储所有的变换信息(只读);
//DOP内部还原的原始位置为rest,注意设置input端口
//直接用rbdbulletsolver(SOP),原始位置还是originP
float bias = chramp('bias', fit(@Frame-@offset*10,75,125,0,1));
matrix3 cm = primintrinsic(0, 'transform', @ptnum);
matrix3 blend = slerp(cm, 3@m, pow(bias,2));
setprimintrinsic(0, 'transform', @ptnum, blend);
v@P = lerp(@P, v@rest, bias);
float bias = chramp('bias', fit(@Frame-@offset*10,75,125,0,1));
matrix fm = getpackedtransform(0, @ptnum);
vector t = cracktransform(0, 0, 0, 0, 4@fm);
translate(4@fm, -t);
translate(4@fm, v@rest);
matrix blend = slerp(fm, 4@fm, bias);
setpackedtransform(0, @ptnum, blend);
案例:拉直螺旋线
- 原理1:以0号点为中心旋转1号点及后续所有点到Y轴上,在以1号点为中心旋转2号点及后续所有点到Y轴上,依次类推;可使用solver或循环(在旋转一次的基础在旋转,容易理解);
- 原理2,每层循环记录上次循环的上一个拉直点(prepos);每层循环先移动到原点旋转Y轴,在加上prepos;
- for等循环体内的point()始终都是读取输入端口的属性,setpointattrib始终会在输出时设置;
//solver节点内,detail层级
int i = @Frame;
vector pos0 = point(0, 'P', i-1);
vector pos1 = point(0, 'P', i);
vector4 rot = dihedral(pos1-pos0, set(0,1,0));vector pos = qrotate(rot, pos1-pos0);
setpointattrib(0, 'P', i, pos+pos0);for(int j=i+1; j<npoints(0); j++){vector pos2 = point(0, 'P', j);pos2 = qrotate(rot, pos2-pos0);setpointattrib(0, 'P', j, pos2+pos0);
}
//point层级,每层循环互不关联
vector prepos = 0;for(int i=1; i< @Frame; i++){vector pivot = point(0, 'P', i-1);vector pos = point(0, 'P', i); vector4 rot = dihedral(pos-pivot, set(0,1,0)); if(@ptnum>=i){vector mpos = qrotate(rot, @P-pivot);//@P=mpos+prepos; //会对下一循环影响setpointattrib(0, 'P', @ptnum, mpos+prepos);}prepos = qrotate(rot, pos-pivot)+prepos;
}