openGL加载obj文件+绘制大脑表层+高亮染色

绘制大脑表层并高亮染色的工作是以openGL加载obj文件为基础的，这里是我们用到的原始程序：只能加载一个obj文件的demo。

然而，一个完整的大脑表层是由很多分区组成的，因此我们的程序需要支持两个功能：

• 同时加载多个obj文件。
• 每个大脑分区obj文件保持其相对位置。

明白了需求后，我们就可以开始修改代码了~

glmUnitize函数的作用是单位化，也就是把模型通过平移和缩放变换限制到3维坐标系中点为中心的一个单位正方体区域内。所以控制obj显示位置是在glmUnitize()函数中，源代码如下：

 /* public functions */

 /* glmUnitize: "unitize" a model by translating it to the origin and
  * scaling it to fit in a unit cube around the origin.  Returns the
  * scalefactor used.
  *
  * model - properly initialized GLMmodel structure
  */
   GLfloat
 glmUnitize(GLMmodel* model, GLfloat center[3])
 {
   GLuint  i;
   GLfloat maxx, minx, maxy, miny, maxz, minz;
   GLfloat cx, cy, cz, w, h, d;
   GLfloat scale;

   assert(model);
   assert(model->vertices);

   /* get the max/mins */
   maxx = minx = model->vertices[3 + X];
   maxy = miny = model->vertices[3 + Y];
   maxz = minz = model->vertices[3 + Z];
   for (i = 1; i <= model->numvertices; i++) {
     if (maxx < model->vertices[3 * i + X])
       maxx = model->vertices[3 * i + X];
     if (minx > model->vertices[3 * i + X])
       minx = model->vertices[3 * i + X];

     if (maxy < model->vertices[3 * i + Y])
       maxy = model->vertices[3 * i + Y];
     if (miny > model->vertices[3 * i + Y])
       miny = model->vertices[3 * i + Y];

     if (maxz < model->vertices[3 * i + Z])
       maxz = model->vertices[3 * i + Z];
     if (minz > model->vertices[3 * i + Z])
       minz = model->vertices[3 * i + Z];
   }

   /* calculate model width, height, and depth */
   w = _glmAbs(maxx) + _glmAbs(minx);
   h = _glmAbs(maxy) + _glmAbs(miny);
   d = _glmAbs(maxz) + _glmAbs(minz);

   /* calculate center of the model */
   cx = (maxx + minx) / 2.0;
   cy = (maxy + miny) / 2.0;
   cz = (maxz + minz) / 2.0;

   /* calculate unitizing scale factor */
   scale = 2.0 / _glmMax(_glmMax(w, h), d);

   /* translate around center then scale */
   for (i = 1; i <= model->numvertices; i++) {
     model->vertices[3 * i + X] -= cx;
     model->vertices[3 * i + Y] -= cy;
     model->vertices[3 * i + Z] -= cz;
     model->vertices[3 * i + X] *= scale;
     model->vertices[3 * i + Y] *= scale;
     model->vertices[3 * i + Z] *= scale;
   }

   center[0] = cx;
   center[1] = cy;
   center[2] = cz;
   return scale;
 }

glmUnitize

这里我们要修改两个内容：

• 删除改变位置的代码
• 改变缩放比例，各个obj文件的缩放因子需要保持一致。

这是修改后的代码：

 /* public functions */

 /* glmUnitize: "unitize" a model by translating it to the origin and
  * scaling it to fit in a unit cube around the origin.  Returns the
  * scalefactor used.
  *
  * model - properly initialized GLMmodel structure
  */
   GLfloat
 glmUnitize(GLMmodel* model, GLfloat center[])
 {
   GLuint  i;
   GLfloat maxx, minx, maxy, miny, maxz, minz;
   GLfloat cx, cy, cz, w, h, d;
   GLfloat scale;

   assert(model);
   assert(model->vertices);

   /* get the max/mins */
   maxx = minx = model->vertices[ + X];
   maxy = miny = model->vertices[ + Y];
   maxz = minz = model->vertices[ + Z];
   for (i = ; i <= model->numvertices; i++) {
     if (maxx < model->vertices[ * i + X])
       maxx = model->vertices[ * i + X];
     if (minx > model->vertices[ * i + X])
       minx = model->vertices[ * i + X];

     if (maxy < model->vertices[ * i + Y])
       maxy = model->vertices[ * i + Y];
     if (miny > model->vertices[ * i + Y])
       miny = model->vertices[ * i + Y];

     if (maxz < model->vertices[ * i + Z])
       maxz = model->vertices[ * i + Z];
     if (minz > model->vertices[ * i + Z])
       minz = model->vertices[ * i + Z];
   }

   /* calculate model width, height, and depth */
   w = _glmAbs(maxx) + _glmAbs(minx);
   h = _glmAbs(maxy) + _glmAbs(miny);
   d = _glmAbs(maxz) + _glmAbs(minz);

   /* calculate center of the model */
   cx = (maxx + minx) / 2.0;
   cy = (maxy + miny) / 2.0;
   cz = (maxz + minz) / 2.0;

   /* calculate unitizing scale factor */
   //scale = 2.0 / _glmMax(_glmMax(w, h), d);
   scale = 0.01;
   /* translate around center then scale */
   for (i = ; i <= model->numvertices; i++) {
    /* model->vertices[3 * i + X] -= cx;
     model->vertices[3 * i + Y] -= cy;
     model->vertices[3 * i + Z] -= cz;*/
     model->vertices[ * i + X] *= scale;
     model->vertices[ * i + Y] *= scale;
     model->vertices[ * i + Z] *= scale;
   }

   center[] = cx;
   center[] = cy;
   center[] = cz;
   return scale;
 }

现在我们要解决同时加载多个obj文件的问题。

• pModel改为pModel数组，全局变量cnt记录当前加载到哪个obj文件。
• 遍历obj文件夹下的所有obj文件，并依次加载。

核心代码如下：

                 case 'o':
         case 'O':
         {
             string path="C:\\test";
             _finddata_t file_info;
             string current_path = path + "/*.obj";
             int handle = _findfirst(current_path.c_str(), &file_info);
             do
             {

                 string rt = "C:\\test\\";
                 string fn= rt + file_info.name;
                 memset(FileName, '\0', sizeof(FileName));
                 for (int i = ; i < fn.length(); i++)
                 {
                     FileName[i] = fn[i];
                 }
                 if (pModel[cnt] == NULL)
                 {
                     pModel[cnt] = glmReadOBJ(FileName);
                     // Generate normal for the model
                     glmFacetNormals(pModel[cnt]);
                     // Scale the model to fit the screen
                     glmUnitize(pModel[cnt], modelCenter);
                     // Init the modelview matrix as an identity matrix
                     glMatrixMode(GL_MODELVIEW);
                     glLoadIdentity();
                     glGetDoublev(GL_MODELVIEW_MATRIX, pModelViewMatrix);
                     cnt++;
                 //    break;
                 }

             } while (!_findnext(handle, &file_info));

             _findclose(handle);
         }

         break;

 void display()
 {
     glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
     glTranslated( 0.0, 0.0, -5.0 );
     glMultMatrixd( pModelViewMatrix );
     for (int i = ; i < cnt; i++)
     {
         if (pModel[i] != NULL)
         {
             glmDraw(pModel[i], GLM_FLAT);
         }
     }
     glutSwapBuffers();
 }

Display

现在我们要给加载的多个obj文件随机染色。

 void Color()
 {
     srand(unsigned(time()));
     for (int i = ; i < maxn; i++)
     {

         rr[i] = random(0.0, 0.7);
         gg[i] = random(0.0, 0.7);
         bb[i] = random(0.0, 0.7);
         cout << rr[i] << " " << gg[i] << " " << bb[i] << endl;
     }
 }

 /// Display the Object
 void display()
 {
     glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();

     glTranslated( 0.0, 0.0, -5.0 );
     glMultMatrixd( pModelViewMatrix );

     glEnable(GL_COLOR_MATERIAL);
     //glColorMaterial(GL_FRONT, GL_DIFFUSE);

     for (int i = ; i < cnt; i++)
     {
         if (pModel[i] != NULL)
         {
             glColor3f(rr[i],gg[i],bb[i]);
             glmDraw(pModel[i], GLM_FLAT|GLM_COLOR);
         }
     }
     glDisable(GL_COLOR_MATERIAL);
     glutSwapBuffers();
 }

到此为止吗，我们就完成了openGL加载obj文件+绘制大脑表层+高亮染色。点击下载：openGLhighlight.zip