Question

我是旧版openGL。我正在场景中绘制多个对象。我希望绘制的球体具有纹理，但所有其他对象都是纯色。但是，如果在绘制球体后尝试禁用纹理，则其他所有颜色均为黑色。

这是我创建纹理的代码

    glGenTextures(1, &textures);
    glBindTexture(GL_TEXTURE_2D, textures);

    glEnable(GL_TEXTURE_2D);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image->Width(), image->Height(), 0, GL_RGB, GL_UNSIGNED_BYTE, image->imageField());
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

这是我画球的地方：

id Objects::sphere(float xPos, float yPos, float zPos){
    const int NR_PHI = 20;
    const int NR_THETA = 20;

    glColor3f(1, 1, 1);

  for(int longitude = 0; longitude < NR_PHI; longitude++)
    for(int latitude = 0; latitude < NR_THETA; latitude++){
      float d_phi   = 2*M_PI/NR_PHI;
      float d_theta = M_PI/NR_THETA; 
      glBegin(GL_TRIANGLES);
      glBindTexture(GL_TEXTURE_2D, textures);
      double x, y, z;

      x = cos(longitude*d_phi)*sin(latitude*d_theta) + xPos;
      y = sin(longitude*d_phi)*sin(latitude*d_theta) + yPos;
      z = cos(latitude*d_theta) + zPos;
      glNormal3f(x, y, z);
      glTexCoord2f(static_cast<float>(longitude)/NR_PHI, static_cast<float>(latitude)/NR_THETA);
      glVertex3f(x, y, z);
      x = cos((longitude+1)*d_phi)*sin(latitude*d_theta) + xPos;
      y = sin((longitude+1)*d_phi)*sin(latitude*d_theta) + yPos;
      z = cos(latitude*d_theta) + zPos;
      glNormal3f(x, y, z);
      glTexCoord2f(d_phi,0);
      glTexCoord2f(static_cast<float>(longitude+1)/NR_PHI, static_cast<float>(latitude)/NR_THETA);
      glVertex3f(x, y, z);
      x = cos((longitude+1)*d_phi)*sin((latitude+1)*d_theta) + xPos;
      y = sin((longitude+1)*d_phi)*sin((latitude+1)*d_theta) + yPos;
      z = cos((latitude+1)*d_theta) + zPos;
      glNormal3f(x, y, z);
      glTexCoord2f(static_cast<float>(longitude+1)/NR_PHI, static_cast<float>(latitude+1)/NR_THETA);
      glVertex3f(x, y, z);      

      x = cos(longitude*d_phi)*sin(latitude*d_theta) + xPos;
      y = sin(longitude*d_phi)*sin(latitude*d_theta) + yPos;
      z = cos(latitude*d_theta) + zPos; 
      glNormal3f(x, y, z);
      glTexCoord2f(static_cast<float>(longitude)/NR_PHI, static_cast<float>(latitude)/NR_THETA);
      glVertex3f(x, y, z);
      x = cos((longitude+1)*d_phi)*sin((latitude+1)*d_theta) + xPos;
      y = sin((longitude+1)*d_phi)*sin((latitude+1)*d_theta) + yPos;
      z = cos((latitude+1)*d_theta) + zPos;
      glNormal3f(x, y, z);
      glTexCoord2f(static_cast<float>(longitude+1)/NR_PHI, static_cast<float>(latitude+1)/NR_THETA);
      glVertex3f(x, y, z);
      x = cos((longitude)*d_phi)*sin((latitude+1)*d_theta) + xPos;
      y = sin((longitude)*d_phi)*sin((latitude+1)*d_theta) + yPos;
      z = cos((latitude+1)*d_theta) + zPos;
      glNormal3f(x, y, z);
      glTexCoord2f(static_cast<float>(longitude)/NR_PHI, static_cast<float>(latitude+1)/NR_THETA);
      glVertex3f(x, y, z);      

      glBindTexture(GL_TEXTURE_2D, 0);     
      glEnd();
  } 
}

Answer 1

You can't call glBindTexture() inside a glBegin()/glEnd() pair:

在glBegin和glEnd之间只能使用GL命令的子集。这些命令是 glVertex， glColor， glSecondaryColor， glIndex， glNormal， glFogCoord， glTexCoord， glMultiTexCoord， glVertexAttrib， glEvalCoord， glEvalPoint， glArrayElement， glMaterial，以及 glEdgeFlag。也，可以使用 glCallList或 glCallLists执行显示仅包含前面命令的列表。 如果在glBegin和glEnd之间执行了其他任何GL命令，设置了错误标志并且忽略了该命令。

请移动glBindTexture()，直到glBegin()前调用几行。

旧版OpenGL纹理无法正常工作

1 个答案: