用于渲染3d球体的纹理坐标

Question

我正在使用GL_QUAD_STRIP原始图绘制3d球体，它的工作原理除了我不知道如何设置纹理坐标。

我有一定数量的division将我的球体划分为相等的纬度和经度数。因此，球体的顶点所使用的划分如下

float x, y, z, dTheta=180/divisions, dLon=360/divisions, degToRad=3.14/180 ; 

    for(float lat =0 ; lat <=180 ; lat+=dTheta) 
    { 
     glBegin(GL_QUAD_STRIP) ; 
     for(float lon = 0 ; lon <=360; lon+=dLon) 
     { 

      x = r*cosf(lat * degToRad) * sinf(lon * degToRad) ; 
      y = r*sinf(lat * degToRad) * sinf(lon * degToRad) ; 
      z = r*cosf(lon * degToRad) ; 

      glNormal3f(x, y, z) ; 
      glVertex3f(x, y, z) ; 

      x = r*cosf((lat + dTheta) * degToRad) * sinf(lon * degToRad) ; 
      y = r*sinf((lat + dTheta) * degToRad) * sinf(lon * degToRad) ; 
      z = r*cosf(lon * degToRad) ; 

      glNormal3f(x, y, z) ; 
      glVertex3f(x, y, z) ; 
     } 
     glEnd() ; 

    } 

Answer 1

好了，问题是，我只是画2个顶点和GL_QUAD_STRIP要求4.下面的代码现已顶点都正确设置和纹理工作

double x, y, z, dTheta=180/divisions, dLon=360/divisions, degToRad=3.141592665885/180 ; 

    for(double lat =0; lat <=180; lat+=dTheta) 
    { 

     glBegin(GL_QUAD_STRIP) ; 
     for(double lon =0 ; lon <=360 ; lon+=dLon) 
     { 


      //Vertex 1 
      x = r*cos(lon * degToRad) * sin(lat * degToRad) ; 
      y = r*sin(lon * degToRad) * sin(lat * degToRad) ; 
      z = r*cos(lat * degToRad) ; 
      glNormal3d(x, y, z) ; 
      glTexCoord2d(lon/360-0.25, lat/180); 
      glVertex3d(x, y, z) ; 


      //Vetex 2 
      x = r*cos(lon * degToRad) * sin((lat + dTheta)* degToRad) ; 
      y = r*sin(lon * degToRad) * sin((lat + dTheta) * degToRad) ; 
      z = r*cos((lat + dTheta) * degToRad) ; 
      glNormal3d(x, y, z) ; 
      glTexCoord2d(lon/360-0.25, (lat + dTheta-1)/(180)); 
      glVertex3d(x, y, z) ; 


      //Vertex 3 
      x = r*cos((lon + dLon) * degToRad) * sin((lat) * degToRad) ; 
      y = r*sin((lon + dLon) * degToRad) * sin((lat) * degToRad) ; 
      z = r*cos((lat) * degToRad) ; 
      glNormal3d(x, y, z) ; 
      glTexCoord2d((lon + dLon)/(360)-0.25 ,(lat)/180); 
      glVertex3d(x, y, z) ; 


      //Vertex 4 
      x = r*cos((lon + dLon) * degToRad) * sin((lat + dTheta)* degToRad) ; 
      y = r*sin((lon + dLon)* degToRad) * sin((lat + dTheta)* degToRad) ; 
      z = r*cos((lat + dTheta)* degToRad) ; 
      glNormal3d(x, y, z) ; 
      glTexCoord2d((lon + dLon)/360-0.25, (lat + dTheta)/(180)); 
      glVertex3d(x, y, z) ; 


     } 
     glEnd() ; 

    } 

谁卡住希望人们可能会发现这很有用。

Answer 2

如果使用标准地distortioned球质地（如通常的地球地图）应该使用纹理坐标等（纬度/ 180，LON/360），即，归一化的近似值范围[0..1]。

Answer 3

添加新的变量：

float texX = 0.0; 
float texy = 0.0; 
float dTex = 1/ divisions; 

然后再加入到循环： 浮子X，Y，Z，dTheta = 180 /司，dLon = 360 /司，degToRad = 3.14/180;

for(float lat =0 ; lat <=180 ; lat+=dTheta, texX += dTex) 
{ 
    texY = 0.0; 
    glBegin(GL_QUAD_STRIP) ; 
    for(float lon = 0 ; lon <=360; lon+=dLon, texY += dTex) 
    { 

     x = r*cosf(lat * degToRad) * sinf(lon * degToRad) ; 
     y = r*sinf(lat * degToRad) * sinf(lon * degToRad) ; 
     z = r*cosf(lon * degToRad) ; 

     glNormal3f(x, y, z) ; 
     glTexCoord2f(texX, texY); 
     glVertex3f(x, y, z) ; 
    } 
    glEnd() ; 

}