openGL 纹理和颜色答案

【问题标题】：openGL texture and colorsopenGL 纹理和颜色
【发布时间】：2011-06-22 18:39:34
【问题描述】：

我正在学习如何在 openGL 中应用纹理。我将纹理应用到立方体的一个面上，并使用原始颜色为其他面着色。在我应用纹理之前，颜色看起来很好，在我应用它之后，它们变得更暗。怎么了？

void LoadGLTextures() {
    // Load Texture
    Image *image1;
    // allocate space for texture
    image1 = (Image *) malloc(sizeof(Image));
    if (image1 == NULL) {
    printf("Error allocating space for image");
    exit(0);
    }

    if (!ImageLoad("dd.bmp", image1)) {
    exit(1);
    }

    // Create Texture
    glGenTextures(1, &texture[0]);
    glBindTexture(GL_TEXTURE_2D, texture[0]);   // 2d texture (x and y size)

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); // scale linearly when image bigger than texture
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); // scale linearly when image smalled than texture

    // 2d texture, level of detail 0 (normal), 3 components (red, green, blue), x size from image, y size from image,
    // border 0 (normal), rgb color data, unsigned byte data, and finally the data itself.
    glTexImage2D(GL_TEXTURE_2D, 0, 3, image1->sizeX, image1->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, image1->data);
}


int main()
{
sf::Window App(sf::VideoMode(600, 600, 32), "SFML OpenGL", sf::Style::Close);
glEnable(GL_DEPTH_TEST);
glDepthMask(GL_TRUE);
glDepthFunc(GL_LEQUAL);
glEnable(GL_TEXTURE_2D);
glShadeModel(GL_SMOOTH);
LoadGLTextures();
glBindTexture(GL_TEXTURE_2D, texture[0]);
while (App.IsOpened())
{
    App.SetActive();
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glBegin(GL_QUADS);
    //back
    glColor3f(0.0f,0.0f,0.0f); //cyan
    glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.2f,0.2f,0.2f); //top left
    glTexCoord2f(1.0f, 1.0f); glVertex3f(0.2f,0.2f,0.2f); //top right
    glTexCoord2f(1.0f, 0.0f); glVertex3f(0.2f,-0.2f,0.2f); //bottom right
    glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.2f,-0.2f,0.2f); //bottom left
    //bottom
    glColor3f(0.0f,1.0f,0.0f); //green
    glVertex3f(0.2f,-0.2f,0.2f); //back right
    glVertex3f(-0.2f,-0.2f,0.2f); //back left
    glVertex3f(-0.2f,-0.2f,-0.2f); //front left
    glVertex3f(0.2f,-0.2f,-0.2f); //front right
    //front
    glColor3f(0.0f,0.0f,1.0f); //blue
    glVertex3f(0.2f,-0.2f,-0.2f); //bottom right
    glVertex3f(-0.2f,-0.2f,-0.2f); //bottom left
    glVertex3f(-0.2f,0.2f,-0.2f); //top left
    glVertex3f(0.2f,0.2f,-0.2f); //top right
    //top
    glColor3f(1.0f,1.0f,0.0f); //yellow
    glVertex3f(0.2f,0.2f,-0.2f); //front right
    glVertex3f(-0.2f,0.2f,-0.2f); //front left
    glVertex3f(-0.2f,0.2f,0.2f); //back left
    glVertex3f(0.2f,0.2f,0.2f); //back right
    //left
    glColor3f(0.0f,1.0f,1.0f); //pink
    glVertex3f(-0.2f,-0.2f,-0.2f); //bottom front
    glVertex3f(-0.2f,-0.2f,0.2f); //bottom back
    glVertex3f(-0.2f,0.2f,0.2f); //top back
    glVertex3f(-0.2f,0.2f,-0.2f); //top front
    //right
    glColor3f(1.0f,0.0f,0.0f); //red
    glVertex3f(0.2f,-0.2f,-0.2f); //bottom front
    glVertex3f(0.2f,-0.2f,0.2f); //bottom back
    glVertex3f(0.2f,0.2f,0.2f); //top back
    glVertex3f(0.2f,0.2f,-0.2f); //top front
    glEnd();

    glFlush();

    App.Display();

    sf::Event Event;
    while (App.GetEvent(Event))
    {
        if (Event.Type == sf::Event::Closed)
            App.Close();
        if ((Event.Type == sf::Event::KeyPressed) && (Event.Key.Code == sf::Key::Escape))
            App.Close();
        if ((Event.Type == sf::Event::KeyPressed) && (Event.Key.Code == sf::Key::Right))
            glRotated(20.0d,0.0d,0.2d,0.0d);
        if ((Event.Type == sf::Event::KeyPressed) && (Event.Key.Code == sf::Key::Left))
            glRotated(-20.0d,0.0d,0.2d,0.0d);
        if ((Event.Type == sf::Event::KeyPressed) && (Event.Key.Code == sf::Key::Up))
            glRotated(20.0d,0.2d,0.0d,0.0d);
        if ((Event.Type == sf::Event::KeyPressed) && (Event.Key.Code == sf::Key::Down))
            glRotated(-20.0d,0.2d,0.0d,0.0d);
        if ((Event.Type == sf::Event::KeyPressed) && (Event.Key.Code == sf::Key::PageUp))
            glRotated(20.0d,0.0d,0.0d,0.2d);
        if ((Event.Type == sf::Event::KeyPressed) && (Event.Key.Code == sf::Key::PageDown))
            glRotated(-20.0d,0.0d,0.0d,0.2d);
    }
}
return EXIT_SUCCESS;
}

【问题讨论】：

如何生成立方体和纹理面？如果您发布一些代码，可能会更容易回答您的问题。
你能给我们看一些代码，或者一张图片吗？谢谢
好的，我看到了LoadGLTextures() 函数，但是你在哪里生成几何图形呢？
有什么想法吗？我只想在一侧应用纹理并让另一侧正确着色。

标签： opengl textures

【解决方案1】：

OpenGL 是一个状态机。这意味着最后一个纹理坐标集将应用于所有后续顶点。因此，即使您停止提供纹理坐标，它仍会在应用到整个面的最后设置的纹理坐标处应用纹理的颜色。

要停止纹理，您必须使用 glDisable(GL_TEXTURE_2D); 禁用纹理，将其放入您的代码中：

// ...
App.SetActive();
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

glEnable(GL_TEXTURE_2D); // <- enable texturing for the one face
glBegin(GL_QUADS);
//back
glColor3f(0.0f,0.0f,0.0f); //cyan
glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.2f,0.2f,0.2f); //top left
glTexCoord2f(1.0f, 1.0f); glVertex3f(0.2f,0.2f,0.2f); //top right
glTexCoord2f(1.0f, 0.0f); glVertex3f(0.2f,-0.2f,0.2f); //bottom right
glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.2f,-0.2f,0.2f); //bottom left
glEnd(); // <- first end the current primitive list

glDisable(GL_TEXTURE_2D); // <- disable texturing for the rest of the faces
glBegin(GL_QUADS);
//bottom
glColor3f(0.0f,1.0f,0.0f); //green
glVertex3f(0.2f,-0.2f,0.2f); //back right
glVertex3f(-0.2f,-0.2f,0.2f); //back left
glVertex3f(-0.2f,-0.2f,-0.2f); //front left
glVertex3f(0.2f,-0.2f,-0.2f); //front right
//front

//...

【讨论】：

启用后，需要绑定一个贴图
@BЈовић：我故意省略了那部分。此外，纹理不会通过禁用纹理来解除绑定。
好的，我刚刚比较了您和他的解决方案（他发布为其他答案）。他的不同之处仅在于绑定。但看看他的问题，我看到他在生成纹理后绑定

【解决方案2】：

尝试在绘制纹理面之前启用 GL_TEXTURE2D，然后立即禁用它。

...
//back
glEnable(GL_TEXTURE2D);
glBegin(GL_QUADS);
glColor3f(0.0f,0.0f,0.0f); //cyan
glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.2f,0.2f,0.2f); //top left
glTexCoord2f(1.0f, 1.0f); glVertex3f(0.2f,0.2f,0.2f); //top right
glTexCoord2f(1.0f, 0.0f); glVertex3f(0.2f,-0.2f,0.2f); //bottom right
glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.2f,-0.2f,0.2f); //bottom left
glEnd();
glDisable(GL_TEXTURE2D);
glBegin(GL_QUADS);
//bottom
...

【讨论】：

glEnable(…)/glDisable(…) 不允许在 glBegin(…)/glEnd() 块内。
-1：因为 OpenGL 不正确。正如 Datenwolf 所说，您不能在 glBegin/glEnd 中间激活或停用纹理。
好的。除此之外 glDisable(GL_TEXTURE2D) 不是解决方案吗？

【解决方案3】：

你完全正确，现在是正确的代码：

    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, texture);
    glBegin(GL_QUADS);
    //back
    glColor3f(1.0f,1.0f,1.0f); //white
    glTexCoord2f(0.0f, 1.0f); glVertex3f(-0.2f,0.2f,0.2f); //top left
    glTexCoord2f(1.0f, 1.0f); glVertex3f(0.2f,0.2f,0.2f); //top right
    glTexCoord2f(1.0f, 0.0f); glVertex3f(0.2f,-0.2f,0.2f); //bottom right
    glTexCoord2f(0.0f, 0.0f); glVertex3f(-0.2f,-0.2f,0.2f); //bottom left
    glEnd();
    glDisable(GL_TEXTURE_2D);
    glBegin(GL_QUADS);
    //bottom
    glColor3f(0.0f,1.0f,0.0f); //green
    glVertex3f(0.2f,-0.2f,0.2f); //back right
    glVertex3f(-0.2f,-0.2f,0.2f); //back left
    glVertex3f(-0.2f,-0.2f,-0.2f); //front left
    glVertex3f(0.2f,-0.2f,-0.2f); //front right
    //front
    glColor3f(0.0f,0.0f,1.0f); //blue
    glVertex3f(0.2f,-0.2f,-0.2f); //bottom right
    glVertex3f(-0.2f,-0.2f,-0.2f); //bottom left
    glVertex3f(-0.2f,0.2f,-0.2f); //top left
    glVertex3f(0.2f,0.2f,-0.2f); //top right
    //top
    glColor3f(1.0f,1.0f,0.0f); //yellow
    glVertex3f(0.2f,0.2f,-0.2f); //front right
    glVertex3f(-0.2f,0.2f,-0.2f); //front left
    glVertex3f(-0.2f,0.2f,0.2f); //back left
    glVertex3f(0.2f,0.2f,0.2f); //back right
    //left
    glColor3f(0.0f,1.0f,1.0f); //pink
    glVertex3f(-0.2f,-0.2f,-0.2f); //bottom front
    glVertex3f(-0.2f,-0.2f,0.2f); //bottom back
    glVertex3f(-0.2f,0.2f,0.2f); //top back
    glVertex3f(-0.2f,0.2f,-0.2f); //top front
    //right
    glColor3f(1.0f,0.0f,0.0f); //red
    glVertex3f(0.2f,-0.2f,-0.2f); //bottom front
    glVertex3f(0.2f,-0.2f,0.2f); //bottom back
    glVertex3f(0.2f,0.2f,0.2f); //top back
    glVertex3f(0.2f,0.2f,-0.2f); //top front
    glEnd();

【讨论】：