OpenGL - 如何滚动纹理？

发布于 2024-10-20 14:22:21 字数 582 浏览 1 评论 0原文

我正在从 pango 布局创建纹理，并使用 OpenGL 和 GLUT 将纹理映射到屏幕。我想滚动窗口中的纹理。我不关心滚动的控件，但如何将我想要看到的纹理部分映射到屏幕上？我假设我使用 glTranslate，但是我在哪里应用它？

提前致谢。

这是我目前所做的：

glEnable(GL_TEXTURE_2D);

{  
  glBegin(GL_QUADS);  

  {  
        glTexCoord2f(0.0f, 0.0f); glVertex2f(  0.0f+x,   0.0f+y);  
        glTexCoord2f(1.0f, 0.0f); glVertex2f(_width+x,   0.0f+y);  
        glTexCoord2f(1.0f, 1.0f); glVertex2f(_width+x, _height+y);  
        glTexCoord2f(0.0f, 1.0f); glVertex2f(  0.0f+x, _height+y);    
  }  

  glEnd();  
}

glFlush();    

glDisable(GL_TEXTURE_2D);

原文

I am creating a texture from a pango layout and mapping the texture to the screen using OpenGL and GLUT. I want to scroll the texture in the window. I'm not concerned with the controls to scroll, but how do I cause map the portion of the texture I want to see onto the screen? I assume I use glTranslate, but where do I apply it?

Thanks in advance.

Here is what I currently do:

glEnable(GL_TEXTURE_2D);

{  
  glBegin(GL_QUADS);  

  {  
        glTexCoord2f(0.0f, 0.0f); glVertex2f(  0.0f+x,   0.0f+y);  
        glTexCoord2f(1.0f, 0.0f); glVertex2f(_width+x,   0.0f+y);  
        glTexCoord2f(1.0f, 1.0f); glVertex2f(_width+x, _height+y);  
        glTexCoord2f(0.0f, 1.0f); glVertex2f(  0.0f+x, _height+y);    
  }  

  glEnd();  
}

glFlush();    

glDisable(GL_TEXTURE_2D);

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不喜欢何必死缠烂打 2024-10-27 14:22:21

另一种方法是使用纹理矩阵（矩阵模式 GL_TEXTURE）或在着色器中进行。

取决于需要修改的顶点数量。如果只有几个顶点，它可能会更高效，但对于许多顶点，纹理矩阵/着色器方法可能会更好。请注意，内置矩阵运算已被弃用，即现在建议使用纹理。

在着色器中滚动很容易：out.tex = in.tex + offset 其中 offset 可以是每帧设置的统一值或根据其他输入计算得出的值。

由于您的示例使用立即模式，因此我将使用纹理矩阵模式对其进行扩展。
但请注意，这是已弃用的方法。

glEnable(GL_TEXTURE_2D);
{
  glMatrixMode(GL_TEXTURE);
  glLoadIndentity();
  glTranslatef(x,y,0);
  glMatrixMode(GL_MODELVIEW);


  glBegin(GL_QUADS);
  {
    glTexCoord2f(0.0f, 0.0f); glVertex2f( 0.0f, 0.0f);
    glTexCoord2f(1.0f, 0.0f); glVertex2f(_width, 0.0f);
    glTexCoord2f(1.0f, 1.0f); glVertex2f(_width, _height);
    glTexCoord2f(0.0f, 1.0f); glVertex2f( 0.0f, _height);
  }
  glEnd();
} 
glFlush();
glDisable(GL_TEXTURE_2D);

Another way would be to use a texture matrix (matrix mode GL_TEXTURE) or do it in a shader.

Depends on how many vertices would have to be modified. If just a few it could be more performant but for many vertices a texture matrix/shader approach could be better. Note that built in matrix operations are deprecated, i.e. it now is recommended to use textures.

Scrolling in a shader would be easy: out.tex = in.tex + offset where offset could be a uniform which is set per frame or be calculated from other input.

Since your example uses immediate mode, I'll expand it with the texture matrix mode.
But please be aware that this is deprecated methodology.

glEnable(GL_TEXTURE_2D);
{
  glMatrixMode(GL_TEXTURE);
  glLoadIndentity();
  glTranslatef(x,y,0);
  glMatrixMode(GL_MODELVIEW);


  glBegin(GL_QUADS);
  {
    glTexCoord2f(0.0f, 0.0f); glVertex2f( 0.0f, 0.0f);
    glTexCoord2f(1.0f, 0.0f); glVertex2f(_width, 0.0f);
    glTexCoord2f(1.0f, 1.0f); glVertex2f(_width, _height);
    glTexCoord2f(0.0f, 1.0f); glVertex2f( 0.0f, _height);
  }
  glEnd();
} 
glFlush();
glDisable(GL_TEXTURE_2D);

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