如何在 3D 图形 OpenGL 中使用纹理

How to use texture in 3d graphic OpenGL

本文关键字:纹理 OpenGL 图形 3D      更新时间:2023-10-16

>正如Tommy所说,我做了一些更改:

所以,我会说步骤是:

  • 确保所有数组中至少有 11 个元素;
  • 启用纹理。

为什么此代码不会显示草纹理?

首先,加载纹理的图像:

QImage img;
if(!img.load("../g.jpg")){
    qDebug("Texture not found!");
}
else {
    t = QGLWidget::convertToGLFormat(img);
    qDebug("Textture Converted to GLFormat.");
}

然后调用应该用顶点数组绘制不平坦地面的 draw 方法:

 GLfloat vertices2[] = {
    2,2,0 , 2,-2,0 , -2,-2,0 , -2,2,0,
    0.7,0.6,0.6 , 0.4,0.9,0.1 , 0.1,0.2,0.3 , 0.8,0.3,0.8 ,
    0.5,-0.5,0.12 , 0,-0.9,0.4 , -0.8,-0.2,0.6
};
GLfloat colors[] = {35 , 73 , 12 , 10 , 6 , 41 , 32 , 10 , 13 , 35 , 42 , 86 , 12 , 2 , 6 ,9};
GLfloat TexCoords[] = {
    0.449,0.911,0.056,
    0.911,0.056,0.17,
    0.056,0.17,0.902,
    0.17,0.902,0.873,
    0.902,0.873,0.061,
    0.873,0.061,0.557,
    0.061,0.557,0.517,
    0.557,0.517,0.131,
    0.517,0.131,0.855,
    0.131,0.855,0.533,
    0.855,0.533,0.896,
    0.533,0.896,0.178,
    0.896,0.178,0.303,
    0.178,0.303,0.358,
    0.303,0.358,0.064,
    0.358,0.064,0.156,
    0.064,0.156,0.199,
    0.156,0.199,0.32,
    0.199,0.32,0.636,
    0.32,0.636,0.306,
    0.636,0.306,0.445,
    0.306,0.445,0.166,
    0.445,0.166,0.572,
    0.166,0.572,0.249,
    0.572,0.249,0.29,
    0.249,0.29,0.389,
    0.29,0.389,0.79,
    0.389,0.79,0.567,
    0.79,0.567,0.692,
    0.567,0.692,0.202,
    0.692,0.202,0.913,
    0.202,0.913,0.498
};
GLfloat NormalP[] = {     0.383,0.29,0.746,
                          0.29,0.746,0.301,
                          0.746,0.301,0.675,
                          0.301,0.675,0.541,
                          0.675,0.541,0.677,
                          0.541,0.677,0.896,
                          0.677,0.896,0.915,
                          0.896,0.915,0.295,
                          0.915,0.295,0.423,
                          0.295,0.423,0.76,
                          0.423,0.76,0.89,
                    };
GLubyte indices[]  = {
    1,2,9 , 9,8,1 , 1,8,7 , 7,1,0 ,
    0,7,4 , 0,4,5 , 0,5,3 , 3,5,6 ,
    3,6,10 , 3,10,2 , 2,10,9 , 9,6,10 ,
    6,5,4 , 6,4,7 , 6,7,8 , 6,8,9
};
GLuint mHandle;
glGenTextures(1, &mHandle);
glBindTexture(GL_TEXTURE_2D, mHandle);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D,0,GL_RGBA,t.width(),t.height(),0,GL_RGBA,GL_UNSIGNED_BYTE,t.bits());
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glColorPointer(3,GL_FLOAT,0,colors);
glVertexPointer(3, GL_FLOAT, 0, vertices2);
glTexCoordPointer(3,GL_FLOAT,0,TexCoords);
glNormalPointer(GL_FLOAT,0,NormalP);
glDrawElements(GL_TRIANGLES,54, GL_UNSIGNED_BYTE, indices);
glDisableClientState(GL_VERTEX_ARRAY);

在固定管线中,仅当启用时才应用纹理。您不显示呼叫glEnable(GL_TEXTURE_2D)

话虽如此,看起来您的数组大小也可能不正确。

glTexCoordPointer(3,GL_FLOAT,0,TexCoords); ... glDrawElements(GL_TRIANGLES,54, GL_UNSIGNED_BYTE, indices);的净效果是将从TexCoords读取 11 组纹理坐标,因为indices中最大的索引是 10 。但是,您的纹理坐标数组中只有两个纹理坐标,前提是您在 3D 中指定它们。

所以,我会说步骤是:

  • 确保所有数组中至少有 11 个元素;
  • 启用纹理。
如果您仅使用 2D 纹理而不对纹理

矩阵堆栈执行任何巧妙的操作,您可能还希望切换到以 2D 形式提供纹理坐标。

根据j-p的说法,公然的抄袭是为什么现在将其标记为社区wiki:创建新纹理ID后,您也无法绑定新纹理ID。OpenGL 有点奇怪,因为纹理 ID 在显示列表被证明不具有最初希望的属性后是一个螺栓,所以你可以侥幸做所有事情,而无需生成纹理,前提是你也从不绑定纹理,假设你只有一个纹理。但是,如果您要对此明智并生成它们,请确保绑定它们。生成不会隐式绑定。

另一个问题是您将 mipmap 作为采样参数的一部分启用:

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);

但是纹理没有 MIPMAP。要生成 mipmap,请在 glTexImage2D() 后添加以下调用:

glGenerateMipmap(GL_TEXTURE_2D);