我想尝试编写类似于此
这样你可以渲染任何线 - 框架网格（甚至 BR 呈现应该以这种方式工作）。
如果您想升级到剪辑，则你应该采取每个线框架线，并计算与切割超平面的交集。如果我们选择超平面，通过点
O（0,0,0，u_cut）且正常 N（ 0,0,0,1）
然后这个任务会简化很多。有3个选项。让我们考虑边缘线与终点 A，B ：
（无交集）
（（Au> u_cut）&&（Bu> u_cut））| | （（Au< u_cut）&（Bu< u_cut））边
1路口
<$ c $ （（Au> = u_cut）&（Bu< = u_cut））|| （（Au = u_cut））so通过线性插值计算交点b $ b $ $ p $ code> x = Ax +（Bx-Ax）*（u_cut-Au）/（Bu-Au ）y = Ay +（By-Ay）*（u_cut-Au）/（Bu-Au）z = Az +（Bz-Az）*（u_cut-Au）/（Bu-Au）
并记住它的属性和边缘。
完全在里面 &（Bu == u_cut）
只要记住两个端点并呈现此边缘即可。
以这种方式处理完所有边后，您需要分析记忆的交点并根据连通性信息创建新边边缘之间。我没有这样做，所以我无法帮助。我会尝试连接共享相同邻居的记住点数，但不确定在 4D 中是否足够。
有关更多信息，请参阅我刚刚发现的相关 QA ：
- 所以我改变了相当多的体系结构。[edit2] solid mesh and cross-section
我将 4D 5x5 均匀转换矩阵（ reper4D ）移至单独的文件并添加了颜色并通过4D单形（4点4个四面体）定义网格。切割只是计算单纯形和切割超平面的交点（如上所述），得到3点（三角形），4点（四面体）或0点。它可以轻松渲染（不需要分析边缘之间的连接）。顺便说一句。我认为这就是
The worst part was to define the hypercube as set of simplexes ...
i want to try writing a playground similar to this 4D toys, so i started learning opengl. from my current understanding, people use VBOs and uniform transformation matrix for mostly-static objects (like cubes, skeletal animations etc., which usually just involves transformations)
i also heard that morphing between models also uses VBOs for caching both models, since both of them will be well defined and not so much intermediates.
but in the 4D toys mentioned above, objects are morphing and clipped a lot. and it is likely that there is no defined models, and many transitions in between. (it might be a simple square now, and a spiky ball clipped in half later ). in this case, is updating-vertex-VBO-per-frame or Vertex Arrays(which i saw in another question) a suitable solution?
解决方案For starters I would use 4D -> 3D projection instead of cut by hyperplane. The result is not the same but will get you closer to your goal (so you can latter upgrade this to cut). So similarly like in 3D -> 2D conversions used in graphics you got 2 choices one is using perspective projection and second is just ignoring the 4th dimension coordinate while rendering. I will use the latter as it is simpler.
structures
To make this as simple as I can I will use wire-frame instead of BR rendering. So you need to handle 4D mesh (wire-frame). I would use 2 tables:
double pnt[]; // 4D point list (x,y,z,u) int lin[]; // lines point indexes (i0,i1)first one stores all the vertexes of your mesh and the second hold index pairs of points connected by lines in wire-frame representation.
transforms
If I would only ignore the 4th coordinate then we would not get the desired functionality. So to make the 4th dimension work we need to add 4D transform to orient our mesh in 4D before rendering. So use homogenous transform matrix and lets call ir rep. In 4D it should be 5x5 orthonormal matrix with 4x4 rotation part rot.
To make this even easier avoid smooth rotations for now (as in 4D that is not as easy) and compute random rotation 4x4 matrix instead. So just set all the cells randomly <-1,+1>. Handle each row as basis vector. To make them orthonormal just make them unit and exploit cross product. For more info see:
- How to generate a randomly oriented, high dimension circle in python?
render
simply convert point table by your transform matrix
(x',y',z',u',W) = rep * (x,y,z,u,1)then take the (x,y,z`) and render ...
no intersection
((A.u > u_cut)&&(B.u > u_cut)) || ((A.u < u_cut)&&(B.u < u_cut))just ignore such edge
1 intersection
((A.u >= u_cut)&&(B.u <= u_cut)) || ((A.u <= u_cut)&&(B.u >= u_cut))so compute the intersection via linear interpolation
x = A.x + (B.x-A.x)*(u_cut-A.u)/(B.u-A.u) y = A.y + (B.y-A.y)*(u_cut-A.u)/(B.u-A.u) z = A.z + (B.z-A.z)*(u_cut-A.u)/(B.u-A.u)and remember such point and also edge to which it belongs to.
fully inside
(A.u == u_cut)&&(B.u == u_cut)just remember both endpoints and also render this edge.
- Visualising 4D objects in OpenGL
- 4D to 3D perspective projection
- 4D rotations
Here simple OpenGL/C++ example of 4D hyper cube:
//--------------------------------------------------------------------------- //--- Mesh 4D: ver 0.000 ---------------------------------------------------- //--------------------------------------------------------------------------- #ifndef _mesh4D_h #define _mesh4D_h //--------------------------------------------------------------------------- #include <math.h> #include "nd_math.h" #include "list.h" //--------------------------------------------------------------------------- const double pi = M_PI; const double pi2 =2.0*M_PI; const double pipol=0.5*M_PI; const double deg=M_PI/180.0; const double rad=180.0/M_PI; //--------------------------------------------------------------------------- class mesh4D { public: matrix<5> rep; // 4D uniform 5x5 transform matrix List<double> pnt; // 4D point list (x,y,z,u) List<int> lin; // lines point indexes (i0,i1) mesh4D() {} mesh4D(mesh4D& a) { *this=a; } ~mesh4D() {} mesh4D* operator = (const mesh4D *a) { *this=*a; return this; } //mesh4D* operator = (const mesh4D &a) { ...copy... return this; } void set_randomrep(); // random oriented uniform 4D transform matrix with origin (0,0,0,0) void set_hypercube(double a); void draw(); }; //--------------------------------------------------------------------------- void mesh4D::set_randomrep() { int i,j; matrix<4> rot; rep.unit(); rot.rnd(); rot.orthonormal(); for (i=0;i<4;i++) for (j=0;j<4;j++) rep[i][j]=rot[i][j]; } void mesh4D::set_hypercube(double a) { rep.unit(); // reset orientation pnt.num=0; // clear point list lin.num=0; // clear line list pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); // A0 lin.add( 0+0); lin.add( 0+1); lin.add( 0+1); lin.add( 0+3); lin.add( 0+3); lin.add( 0+2); lin.add( 0+2); lin.add( 0+0); // A1 lin.add( 4+0); lin.add( 4+1); lin.add( 4+1); lin.add( 4+3); lin.add( 4+3); lin.add( 4+2); lin.add( 4+2); lin.add( 4+0); // A=A0+A1 lin.add( 0+0); lin.add( 4+0); lin.add( 0+1); lin.add( 4+1); lin.add( 0+2); lin.add( 4+2); lin.add( 0+3); lin.add( 4+3); // B0 lin.add( 8+0); lin.add( 8+1); lin.add( 8+1); lin.add( 8+3); lin.add( 8+3); lin.add( 8+2); lin.add( 8+2); lin.add( 8+0); // B1 lin.add(12+0); lin.add(12+1); lin.add(12+1); lin.add(12+3); lin.add(12+3); lin.add(12+2); lin.add(12+2); lin.add(12+0); // B=B0+B1 lin.add( 8+0); lin.add(12+0); lin.add( 8+1); lin.add(12+1); lin.add( 8+2); lin.add(12+2); lin.add( 8+3); lin.add(12+3); // hyper cube = A+B lin.add( 0+0); lin.add( 8+0); lin.add( 0+1); lin.add( 8+1); lin.add( 0+2); lin.add( 8+2); lin.add( 0+3); lin.add( 8+3); lin.add( 0+4); lin.add( 8+4); lin.add( 0+5); lin.add( 8+5); lin.add( 0+6); lin.add( 8+6); lin.add( 0+7); lin.add( 8+7); } //--------------------------------------------------------------------------- void mesh4D::draw() { int i,j; double _zero=1e-3; vector<5> a,b; glBegin(GL_LINES); for (i=0;i<lin.num;) { // extrac first point j=lin[i]*4; i++; a.a[0]=pnt[j]; j++; a.a[1]=pnt[j]; j++; a.a[2]=pnt[j]; j++; a.a[3]=pnt[j]; j++; a.a[4]=1.0; // W=1 // extrac second point j=lin[i]*4; i++; b.a[0]=pnt[j]; j++; b.a[1]=pnt[j]; j++; b.a[2]=pnt[j]; j++; b.a[3]=pnt[j]; j++; b.a[4]=1.0; // W=1 // transform a=rep*a; b=rep*b; // render glVertex3dv(a.a); // use just x,y,z glVertex3dv(b.a); // use just x,y,z } glEnd(); } //--------------------------------------------------------------------------- #endif //---------------------------------------------------------------------------I used mine dynamic list.h template so:
List<double> xxx; is the same as double xxx[]; xxx.add(5); adds 5 to end of the list xxx[7] access array element (safe) xxx.dat[7] access array element (unsafe but fast direct access) xxx.num is the actual used size of the array xxx.reset() clears the array and set xxx.num=0 xxx.allocate(100) preallocate space for 100 items
the nd_math.h is mine lib for N-Dimensional computations. What you need is just 4D,5D vector and 4x4, 5x5 matrix math from linear algebra.
Both libs are a bit big in size and also legal issues prevent me to share their code here.
The usage is simple:
// globals and init mesh4D mesh double animx=-50.0,danimx=0.0; double animy= 0.0,danimy=2.0; mesh.set_hypercube(0.5); // render glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D( -2.0, 2.0, -2.0, 2.0 ); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glRotated(animx,1.0,0.0,0.0); glRotated(animy,0.0,1.0,0.0); mesh.draw(); glFlush(); SwapBuffers(hdc); // some timer animx+=danimx; if (animx>=360.0) animx-=360.0; animy+=danimy; if (animy>=360.0) animy-=360.0; call_render_here(); // on key press or mouse wheel or what ever mesh.set_randomrep();And here preview for some rep rotations ...
so this way you can render any wire-frame mesh (even BR rendering should works this way).
If you want to upgrade to the cut then you should take each Wire-frame line and compute its intersection with cutting hyperplane. If we chose hyperplane that goes through point
O(0,0,0,u_cut)and has normal
N(0,0,0,1)Then the task will simplify a lot. there are 3 options. Lets consider edge line with endpoints A,B:
After all edges are processed this way then you need to analyze the remembered intersection points and create new edges from them based on connectivity info between edges. I did not do this yet so I can not help with this. I would try to connect remembered points sharing the same neighbor but not sure if that is enough in 4D.
For more info take a look at related QAs I just found:
[Edit1] code with perspective
//--------------------------------------------------------------------------- //--- Mesh 4D: ver 0.001 ---------------------------------------------------- //--------------------------------------------------------------------------- #ifndef _mesh4D_h #define _mesh4D_h //--------------------------------------------------------------------------- #include <math.h> #include "nd_math.h" #include "list.h" //--------------------------------------------------------------------------- const double pi = M_PI; const double pi2 =2.0*M_PI; const double pipol=0.5*M_PI; const double deg=M_PI/180.0; const double rad=180.0/M_PI; //--------------------------------------------------------------------------- class mesh4D { public: matrix<5> rep; // 4D uniform 5x5 transform matrix List<double> pnt; // 4D point list (x,y,z,u) List<int> lin; // lines point indexes (i0,i1) mesh4D() {} mesh4D(mesh4D& a) { *this=a; } ~mesh4D() {} mesh4D* operator = (const mesh4D *a) { *this=*a; return this; } //mesh4D* operator = (const mesh4D &a) { ...copy... return this; } void set_randomrep(); // random oriented uniform 4D transform matrix with origin (0,0,0,0) void set_hypercube(double a); void draw(); }; //--------------------------------------------------------------------------- void mesh4D::set_randomrep() { int i,j; matrix<4> rot; rot.rnd(); rot.orthonormal(); for (i=0;i<4;i++) for (j=0;j<4;j++) rep[i][j]=rot[i][j]; } //--------------------------------------------------------------------------- void mesh4D::set_hypercube(double a) { rep.unit(); // reset orientation rep[0][4]=0.0; // set position rep[1][4]=0.0; rep[2][4]=0.0; rep[3][4]=3.0*a; pnt.num=0; // clear point list lin.num=0; // clear line list pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(-a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(-a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); pnt.add(+a); // A0 lin.add( 0+0); lin.add( 0+1); lin.add( 0+1); lin.add( 0+3); lin.add( 0+3); lin.add( 0+2); lin.add( 0+2); lin.add( 0+0); // A1 lin.add( 4+0); lin.add( 4+1); lin.add( 4+1); lin.add( 4+3); lin.add( 4+3); lin.add( 4+2); lin.add( 4+2); lin.add( 4+0); // A=A0+A1 lin.add( 0+0); lin.add( 4+0); lin.add( 0+1); lin.add( 4+1); lin.add( 0+2); lin.add( 4+2); lin.add( 0+3); lin.add( 4+3); // B0 lin.add( 8+0); lin.add( 8+1); lin.add( 8+1); lin.add( 8+3); lin.add( 8+3); lin.add( 8+2); lin.add( 8+2); lin.add( 8+0); // B1 lin.add(12+0); lin.add(12+1); lin.add(12+1); lin.add(12+3); lin.add(12+3); lin.add(12+2); lin.add(12+2); lin.add(12+0); // B=B0+B1 lin.add( 8+0); lin.add(12+0); lin.add( 8+1); lin.add(12+1); lin.add( 8+2); lin.add(12+2); lin.add( 8+3); lin.add(12+3); // hyper cube = A+B lin.add( 0+0); lin.add( 8+0); lin.add( 0+1); lin.add( 8+1); lin.add( 0+2); lin.add( 8+2); lin.add( 0+3); lin.add( 8+3); lin.add( 0+4); lin.add( 8+4); lin.add( 0+5); lin.add( 8+5); lin.add( 0+6); lin.add( 8+6); lin.add( 0+7); lin.add( 8+7); } //--------------------------------------------------------------------------- void mesh4D::draw() { int i,j; const double _zero=1e-3; double focal_length=1.0; vector<5> a,b; glBegin(GL_LINES); for (i=0;i<lin.num;) { // extrac first point j=lin[i]*4; i++; a.a[0]=pnt[j]; j++; a.a[1]=pnt[j]; j++; a.a[2]=pnt[j]; j++; a.a[3]=pnt[j]; j++; a.a[4]=1.0; // W=1 // extrac second point j=lin[i]*4; i++; b.a[0]=pnt[j]; j++; b.a[1]=pnt[j]; j++; b.a[2]=pnt[j]; j++; b.a[3]=pnt[j]; j++; b.a[4]=1.0; // W=1 // transform a=rep*a; b=rep*b; // perspective: camera projection plane u=0, focus at (0,0,0,-focal_length) if (a[3]>=0.0) a*=divide(focal_length,a[3]+focal_length); else a.zero(); if (b[3]>=0.0) b*=divide(focal_length,b[3]+focal_length); else b.zero(); // render glVertex3dv(a.a); // use just x,y,z glVertex3dv(b.a); // use just x,y,z } glEnd(); } //--------------------------------------------------------------------------- #endif //---------------------------------------------------------------------------And preview:
[Edit2] solid mesh and cross-section
so I changed the architecture quite a bit. I moved the 4D 5x5 homogenuous transform matrix (reper4D) to separate file and added colors and mesh definition by 4D simplexes (4 point 4 side tetrahedrons). The cut is simply computing the intersection (as described above) of simplex and cutting hyperplane resulting in either 3 points (triangle) , 4 points (tetrahedron) or 0 points. Which can be rendered easily (no need to analyze the connections between edges). Btw. I think this is how Miegakure works. Here updated code:
//--------------------------------------------------------------------------- //--- Mesh 4D: ver 1.000 ---------------------------------------------------- //--------------------------------------------------------------------------- #ifndef _mesh4D_h #define _mesh4D_h //--------------------------------------------------------------------------- #include "list.h" #include "reper4D.h" //--------------------------------------------------------------------------- class mesh4D { public: reper4D rep; // 4D uniform 5x5 transform matrix List<double> pnt; // 4D point list (x,y,z,w) List<int> lin; // 4D wireframe (i0,i1) List<int> fac; // 4D simplexes (i0,i1,i2,i3) List<DWORD> col; // simplex colors (RGB) mesh4D() {} mesh4D(mesh4D& a) { *this=a; } ~mesh4D() {} mesh4D* operator = (const mesh4D *a) { *this=*a; return this; } //mesh4D* operator = (const mesh4D &a) { ...copy... return this; } void set_hypercube(double a); void draw_cut(double w_cut); // render cross section by w=w_cut hyperplane void draw (double focal_length=-1.0,double w_near=-1.0); // render mesh (focal_length<0) -> no perspective, else perspective view in W+ direction void draw_wireframe(double focal_length=-1.0,double w_near=-1.0); // render wireframe (focal_length<0) -> no perspective, else perspective view in W+ direction }; //--------------------------------------------------------------------------- void mesh4D::set_hypercube(double a) { const double tab_pnt[]= { -a, -a, -a, -a, +a, -a, -a, -a, -a, +a, -a, -a, +a, +a, -a, -a, -a, -a, +a, -a, +a, -a, +a, -a, -a, +a, +a, -a, +a, +a, +a, -a, -a, -a, -a, +a, +a, -a, -a, +a, -a, +a, -a, +a, +a, +a, -a, +a, -a, -a, +a, +a, +a, -a, +a, +a, -a, +a, +a, +a, +a, +a, +a, +a, }; const int tab_lin[]= { // A0 0+0, 0+1, 0+1, 0+3, 0+3, 0+2, 0+2, 0+0, // A1 4+0, 4+1, 4+1, 4+3, 4+3, 4+2, 4+2, 4+0, // A=A0+A1 0+0, 4+0, 0+1, 4+1, 0+2, 4+2, 0+3, 4+3, // B0 8+0, 8+1, 8+1, 8+3, 8+3, 8+2, 8+2, 8+0, // B1 12+0, 12+1, 12+1, 12+3, 12+3, 12+2, 12+2, 12+0, // B=B0+B1 8+0, 12+0, 8+1, 12+1, 8+2, 12+2, 8+3, 12+3, // hyper cube = A+B 0+0, 8+0, 0+1, 8+1, 0+2, 8+2, 0+3, 8+3, 0+4, 8+4, 0+5, 8+5, 0+6, 8+6, 0+7, 8+7, }; // 5x simplex per cube #define _cube(a0,a1,a2,a3,a4,a5,a6,a7) a1,a2,a4,a7, a0,a1,a2,a4, a2,a4,a6,a7, a1,a2,a3,a7, a1,a4,a5,a7 // 4D hypercube = 8 cubes const int tab_fac[]= { _cube( 0, 1, 2, 3, 4, 5, 6, 7), _cube( 0, 1, 2, 3, 8, 9,10,11), _cube( 4, 5, 6, 7,12,13,14,15), _cube( 8, 9,10,11,12,13,14,15), _cube( 0, 1, 4, 5, 8, 9,12,13), _cube( 0, 2, 4, 6, 8,10,12,14), _cube( 1, 3, 5, 7, 9,11,13,15), _cube( 2, 3, 6, 7,10,11,14,15), }; #undef _cube const DWORD tab_col[]= { // BBGGRR, BBGGRR, BBGGRR, BBGGRR, BBGGRR, 0x00FF0000,0x00FF0000,0x00FF0000,0x00FF0000,0x00FF0000, 0x0000FF00,0x0000FF00,0x0000FF00,0x0000FF00,0x0000FF00, 0x000000FF,0x000000FF,0x000000FF,0x000000FF,0x000000FF, 0x0000FFFF,0x0000FFFF,0x0000FFFF,0x0000FFFF,0x0000FFFF, 0x00FF00FF,0x00FF00FF,0x00FF00FF,0x00FF00FF,0x00FF00FF, 0x00FFFF00,0x00FFFF00,0x00FFFF00,0x00FFFF00,0x00FFFF00, 0x00FFFFFF,0x00FFFFFF,0x00FFFFFF,0x00FFFFFF,0x00FFFFFF, 0x004080FF,0x004080FF,0x004080FF,0x004080FF,0x004080FF, }; int i,n; vector<4> p; rep.reset(); pnt.num=0; for (i=0,n=sizeof(tab_pnt)/sizeof(tab_pnt[0]);i<n;i++) pnt.add(tab_pnt[i]); lin.num=0; for (i=0,n=sizeof(tab_lin)/sizeof(tab_lin[0]);i<n;i++) lin.add(tab_lin[i]); fac.num=0; for (i=0,n=sizeof(tab_fac)/sizeof(tab_fac[0]);i<n;i++) fac.add(tab_fac[i]); col.num=0; for (i=0,n=sizeof(tab_col)/sizeof(tab_col[0]);i<n;i++) col.add(tab_col[i]); } //--------------------------------------------------------------------------- void mesh4D::draw_cut(double w_cut) { const double _zero=1e-6; const int edge2[]={0,1,0,2,0,3,1,2,2,3,3,1,-1}; // simplex wireframe i0,i1 const int edge3[]={0,1,2,3,0,1,3,1,2,3,2,0,-1}; // simplex triangles i0,i1,i2 int e,i,j,k,k0,k1,k2,inside[4]; DWORD rgb; vector<4> p[4],q[4]; vector<3> xyz[4],nor,a,b; for (i=0;i<fac.num;) { rgb=col[i>>2]; // extrac points (x,y,z,w) for (k=0;k<4;k++) { j=fac[i]*4; i++; p[k].a[0]=pnt[j]; j++; p[k].a[1]=pnt[j]; j++; p[k].a[2]=pnt[j]; j++; p[k].a[3]=pnt[j]; j++; // transform rep.l2g(p[k],p[k]); inside[k]=1; } // process edge2 and compute cross section cut intersection points for (e=0,k=0;edge2[e]>=0;) { k0=edge2[e]; e++; k1=edge2[e]; e++; // fully inside if (fabs(p[k0][3]-w_cut)+fabs(p[k1][3]-w_cut)<=_zero) { if ((k<4)&&(inside[k0])){ q[k]=p[k0]; k++; inside[k0]=0; } if ((k<4)&&(inside[k1])){ q[k]=p[k1]; k++; inside[k1]=0; } continue; } // no intersection if (((p[k0][3]> w_cut)&&(p[k1][3]> w_cut))||((p[k0][3]< w_cut)&&(p[k1][3]< w_cut))) continue; // 1 intersection if (k<4) { q[k]=p[k1]-p[k0]; q[k]*=divide(w_cut-p[k0][3],p[k1][3]-p[k0][3]); q[k]+=p[k0]; q[k][3]=w_cut; k++; continue; } } // 4D -> 3D vector for (k0=0;k0<k;k0++) for (k1=0;k1<3;k1++) xyz[k0][k1]=q[k0][k1]; // render triangle if (k==3) { // normal a=xyz[1]-xyz[0]; b=xyz[2]-xyz[1]; nor.cross(a,b); nor.unit(); // render glBegin(GL_TRIANGLES); glNormal3dv(nor.a); glColor4ubv((BYTE*)(&rgb)); glVertex3dv(xyz[0].a); glVertex3dv(xyz[1].a); glVertex3dv(xyz[2].a); glEnd(); } // render simplex if (k==4) for (e=0;edge3[e]>=0;) { k0=edge3[e]; e++; k1=edge3[e]; e++; k2=edge3[e]; e++; // normal a=xyz[k1]-xyz[k0]; b=xyz[k2]-xyz[k1]; nor.cross(a,b); nor.unit(); // render glBegin(GL_TRIANGLES); glNormal3dv(nor.a); glColor4ubv((BYTE*)(&rgb)); glVertex3dv(xyz[k0].a); glVertex3dv(xyz[k1].a); glVertex3dv(xyz[k2].a); glEnd(); } } } //--------------------------------------------------------------------------- void mesh4D::draw(double focal_length,double w_near) { const int edge3[]={0,1,2,3,0,1,3,1,2,3,2,0,-1}; // simplex triangles i0,i1,i2 int i,j,k,k0,k1,k2; DWORD rgb; vector<4> p; vector<3> xyz[4],nor,a,b; // 4D simplexes glColor3f(0.3,0.3,0.3); for (i=0;i<fac.num;) { rgb=col[i>>2]; // extrac points (x,y,z,w) for (k=0;k<4;k++) { j=fac[i]*4; i++; p[0]=pnt[j]; j++; p[1]=pnt[j]; j++; p[2]=pnt[j]; j++; p[3]=pnt[j]; j++; // transform rep.l2g(p,p); // perspective projection if (focal_length>0.0) { p[3]-=w_near; if (p[3]>=0.0) p*=divide(focal_length,p[3]+focal_length); else p.zero(); } // 4D -> 3D vector xyz[k].ld(p[0],p[1],p[2]); } // render simplex for (k=0;edge3[k]>=0;) { k0=edge3[k]; k++; k1=edge3[k]; k++; k2=edge3[k]; k++; // normal a=xyz[k1]-xyz[k0]; b=xyz[k2]-xyz[k1]; nor.cross(a,b); nor.unit(); // render // glBegin(GL_LINE_LOOP); glBegin(GL_TRIANGLES); glNormal3dv(nor.a); glColor4ubv((BYTE*)(&rgb)); glVertex3dv(xyz[k0].a); glVertex3dv(xyz[k1].a); glVertex3dv(xyz[k2].a); glEnd(); } } } //--------------------------------------------------------------------------- void mesh4D::draw_wireframe(double focal_length,double w_near) { int i,j,k; vector<4> p[4]; // 4D wireframe glColor3f(1.0,1.0,1.0); glBegin(GL_LINES); for (i=0;i<lin.num;) { // extrac points (x,y,z,w) for (k=0;k<2;k++) { j=lin[i]*4; i++; p[k].a[0]=pnt[j]; j++; p[k].a[1]=pnt[j]; j++; p[k].a[2]=pnt[j]; j++; p[k].a[3]=pnt[j]; j++; // transform rep.l2g(p[k],p[k]); // perspective projection if (focal_length>0.0) { p[k][3]-=w_near; if (p[k][3]>=0.0) p[k]*=divide(focal_length,p[k][3]+focal_length); else p[k].zero(); } // render glVertex3dv(p[k].a); // use just x,y,z } } glEnd(); } //--------------------------------------------------------------------------- #endif //---------------------------------------------------------------------------And the preview for cross section render:
The worst part was to define the hypercube as set of simplexes ...
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