Torus 的纹理应用不正确

Question

我正在创建一个带有 6 Torus 的开放式 GL 程序。当我应用纹理时，它以一种颜色显示。尽管它不是单一的颜色。

我正在从数组中获取图像。除 Torus 纹理外，其他纹理（天空盒、行星、HUD）应用正确。我也尝试使用光源，但没有成功。有人可以帮我实现这个目标吗？

下面是我的代码。

                glPushMatrix();
                glEnable(GL_TEXTURE_2D);
                glTranslatef(xpos, ypos, zpos);
                glRotatef(fPlanetRot, 0.0f, -1.0f, 0.0f);
                glColor3f(0.0, 0.0, 0.0);

                // Select the texture object
                glBindTexture(GL_TEXTURE_2D, textures[3]);

                glutSolidTorus(0.1, 1.0, 30, 30);
                glDisable(GL_TEXTURE_2D);
                glPopMatrix();

//This is where I load the texture

void SetupRC()
{
    //textures

    GLuint texture;
    // allocate a texture name
    glGenTextures( 1, &texture );
    glPixelStorei(GL_UNPACK_ALIGNMENT,1);

    //there are quite a few ways of loading images
    // Load textures in a for loop
    glGenTextures(TEXTURE_COUNT, textures);
    //this puts the texture into OpenGL texture memory
 //   glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE); - not defined so probably need to update GLEW - not needed here so ignore
    for(int iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++)
    {
        // Bind to next texture object
        glBindTexture(GL_TEXTURE_2D, textures[iLoop]);
        
        // Load texture data, set filter and wrap modes
        //note that gltLoadTGA is in the glm.cpp file and not a built-in openGL function
        pBytes0 = gltLoadTGA(textureFiles[iLoop],&iWidth, &iHeight,
                             &iComponents, &eFormat);
        
        glTexImage2D(GL_TEXTURE_2D, 0, iComponents, iWidth, iHeight, 0, eFormat, GL_UNSIGNED_BYTE, pBytes0);
        
            //set up texture parameters
        
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
        //try these too
        glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_ADD);
         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
        free(pBytes0);
    }
    
    //enable textures
    glEnable(GL_TEXTURE_2D);

    
    glEnable(GL_DEPTH_TEST);    // Hidden surface removal    
    glFrontFace(GL_CCW);// Counter clock-wise polygons face out
    glEnable(GL_CULL_FACE);     // Do not calculate inside

//    glCullFace(GL_FRONT_AND_BACK);
    
    // Enable lighting
    glEnable(GL_LIGHTING);
    glEnable(GL_POINT_SMOOTH);
    // Setup and enable light 0
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT,whiteLightLessBright);
    glLightfv(GL_LIGHT0,GL_DIFFUSE,redLight);
    glLightfv(GL_LIGHT0,GL_POSITION,lightPos);
    glEnable(GL_LIGHT0);

    // Enable colour tracking
    glEnable(GL_COLOR_MATERIAL);
    
    // Set Material properties to follow glColor values
    glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
    
    // Black blue background
    glClearColor(0.0f, 0.0f, 0.03f, 1.0f );
}

Answer 1

简而言之：

glutSolidTorus() 只是不发出环面的纹理坐标，而只发出坐标和每个顶点的法线。

长话短说：

出于好奇，我谷歌了一下，我相信我找到了对 OP 观察的解释

Other textures (skybox, planet, HUD) are applying properly except Torus textures.

首先我看了一下文档。 11.4 glutSolidTorus, glutWireTorus 但我找不到任何提示是否支持或不支持纹理坐标。我尝试了其他一些文档，但大多数都是此文档的副本，或者也没有提到纹理。

接下来我试图找到“glutSolidTorus 纹理”的示例图像，但我找不到。

非常可疑……

所以，我终于在github上看到了glutSolidTorus()的源代码：

void APIENTRY
glutSolidTorus(GLdouble innerRadius, GLdouble outerRadius,
  GLint nsides, GLint rings)
{
  doughnut(innerRadius, outerRadius, nsides, rings);
}

doughnut()函数定义在同一个源文件中：

static void
doughnut(GLfloat r, GLfloat R, GLint nsides, GLint rings)
{
  int i, j;
  GLfloat theta, phi, theta1;
  GLfloat cosTheta, sinTheta;
  GLfloat cosTheta1, sinTheta1;
  GLfloat ringDelta, sideDelta;

  ringDelta = 2.0 * M_PI / rings;
  sideDelta = 2.0 * M_PI / nsides;

  theta = 0.0;
  cosTheta = 1.0;
  sinTheta = 0.0;
  for (i = rings - 1; i >= 0; i--) {
    theta1 = theta + ringDelta;
    cosTheta1 = cos(theta1);
    sinTheta1 = sin(theta1);
    glBegin(GL_QUAD_STRIP);
    phi = 0.0;
    for (j = nsides; j >= 0; j--) {
      GLfloat cosPhi, sinPhi, dist;

      phi += sideDelta;
      cosPhi = cos(phi);
      sinPhi = sin(phi);
      dist = R + r * cosPhi;

      glNormal3f(cosTheta1 * cosPhi, -sinTheta1 * cosPhi, sinPhi);
      glVertex3f(cosTheta1 * dist, -sinTheta1 * dist, r * sinPhi);
      glNormal3f(cosTheta * cosPhi, -sinTheta * cosPhi, sinPhi);
      glVertex3f(cosTheta * dist, -sinTheta * dist,  r * sinPhi);
    }
    glEnd();
    theta = theta1;
    cosTheta = cosTheta1;
    sinTheta = sinTheta1;
  }
}

答案简单明了——glutSolidTorus() 只是不发出环面的纹理坐标，而只发出坐标和每个顶点的法线。因此，所有像素从一开始就将具有相同且唯一的纹理坐标。这将导致颜色均匀的环面（如 OP 所观察到的那样）。

所以，当 glutSolidTorus() 不支持纹理时，为什么glutSolidSphere()？同源文件中给出了答案：

void APIENTRY
glutSolidSphere(GLdouble radius, GLint slices, GLint stacks)
{
  QUAD_OBJ_INIT();
  gluQuadricDrawStyle(quadObj, GLU_FILL);
  gluQuadricNormals(quadObj, GLU_SMOOTH);
  /* If we ever changed/used the texture or orientation state
     of quadObj, we'd need to change it to the defaults here
     with gluQuadricTexture and/or gluQuadricOrientation. */
  gluSphere(quadObj, radius, slices, stacks);
}

即glutSolidSphere() 只是 gluSphere() 的包装。医生。 gluSphere() 的人明确提到纹理：

If texturing is turned on (with gluQuadricTexture), then texture coordinates are generated so that t ranges from 0.0 at z = - radius to 1.0 at z = radius (t increases linearly along longitudinal lines), and s ranges from 0.0 at the +y axis, to 0.25 at the +x axis, to 0.5 at the -y axis, to 0.75 at the -x axis, and back to 1.0 at the +y axis.

如果 OP 打算拥有带纹理的环面，则 glutSolidTorus() 必须替换为发出纹理坐标的自定义版本。使用给定的源代码，扩展函数应该不会太难。（请不要忘记给它一个新名称，以防止 link 符号重复定义错误 glutSolidTorus()…）

我后来找到的有用链接：

（可能重复但 [closed]）
3D Opengl Graphics: Texture mapping on Torus

Torus 的纹理应用不正确

Texture for Torus is not applying properly

c++

opengl

textures

opengl-compat