剛寫了一個OpenGL字體顯示類, 發現顏色總是不對, 部分代碼如下:

????//繪制文字
????glPushAttrib(GL_LIST_BIT?|?GL_COLOR_BUFFER_BIT?|?GL_ENABLE_BIT);
????glDisable(GL_LIGHTING);

????//文字位置
????if(m_screen)
????{
????????double?x=m_x,y=m_y;
????????switch(m_layout)
????????{
????????case(LEFT_BOTTOM):break;
????????case(LEFT_TOP):///左上角
????????????y?=?m_parent->GetGLWindow()->GetSize().y-m_y;
????????????break;
????????case(RIGHT_BOTTOM):///右下角
????????????x?=?m_parent->GetGLWindow()->GetSize().x-m_x;
????????????break;
????????case(RIGHT_TOP):///右上角
????????????x?=?m_parent->GetGLWindow()->GetSize().x-m_x;
????????????y?=?m_parent->GetGLWindow()->GetSize().y-m_y;
????????????break;
????????case(LEFT_CENTER):///左側中心
????????????y?=?0.5*m_parent->GetGLWindow()->GetSize().y+m_y;
????????????break;
????????case(TOP_CENTER):///頂部中心
????????????x?=?0.5*m_parent->GetGLWindow()->GetSize().x+m_x;
????????????y?=?m_parent->GetGLWindow()->GetSize().y-m_y;
????????????break;
????????case(BOTTOM_CENTER):///底部中性
????????????x?=?0.5*m_parent->GetGLWindow()->GetSize().x+m_x;
????????????break;
????????case(RIGHT_CENTER):///右側中心
????????????x?=?m_parent->GetGLWindow()->GetSize().x-m_x;
????????????y?=?0.5*m_parent->GetGLWindow()->GetSize().y+m_y;
????????????break;
????????case(CENTER):///屏幕中心
????????????x?=?0.5*m_parent->GetGLWindow()->GetSize().x+m_x;
????????????y?=?0.5*m_parent->GetGLWindow()->GetSize().y+m_y;
????????????break;
????????}
????????glWindowPos2d(x,y);
????}
????else
????????glRasterPos3d(m_x,m_y,m_z);
????
????//文字顏色,必須在glWindowPos2d和glRasterPos3d前
????glColor4fv(Color);?//<------

????//調用顯示列表
????glListBase(m_base);
????glCallLists(m_list_len,GL_UNSIGNED_INT,m_lists);
????glPopAttrib();

?

百思不得其解, 翻開Red Book找到了答案:

? 8.1.3 選擇位圖的顏色

? ... 光柵顏色狀態變量被設置為調用函數glRasterPos*()時的顏色, ...

?

顯然只需要調整glColor*和 glRasterPos*的位置即可, 修改后的代碼如下:

????//繪制文字
????glPushAttrib(GL_LIST_BIT?|?GL_COLOR_BUFFER_BIT?|?GL_ENABLE_BIT);
????glDisable(GL_LIGHTING);

????//文字顏色,必須在glWindowPos2d和glRasterPos3d前
????glColor4fv(Color);

????//文字位置
????if(m_screen)
????{
????????double?x=m_x,y=m_y;
????????switch(m_layout)
????????{
????????case(LEFT_BOTTOM):break;
????????case(LEFT_TOP):///左上角
????????????y?=?m_parent->GetGLWindow()->GetSize().y-m_y;
????????????break;
????????case(RIGHT_BOTTOM):///右下角
????????????x?=?m_parent->GetGLWindow()->GetSize().x-m_x;
????????????break;
????????case(RIGHT_TOP):///右上角
????????????x?=?m_parent->GetGLWindow()->GetSize().x-m_x;
????????????y?=?m_parent->GetGLWindow()->GetSize().y-m_y;
????????????break;
????????case(LEFT_CENTER):///左側中心
????????????y?=?0.5*m_parent->GetGLWindow()->GetSize().y+m_y;
????????????break;
????????case(TOP_CENTER):///頂部中心
????????????x?=?0.5*m_parent->GetGLWindow()->GetSize().x+m_x;
????????????y?=?m_parent->GetGLWindow()->GetSize().y-m_y;
????????????break;
????????case(BOTTOM_CENTER):///底部中性
????????????x?=?0.5*m_parent->GetGLWindow()->GetSize().x+m_x;
????????????break;
????????case(RIGHT_CENTER):///右側中心
????????????x?=?m_parent->GetGLWindow()->GetSize().x-m_x;
????????????y?=?0.5*m_parent->GetGLWindow()->GetSize().y+m_y;
????????????break;
????????case(CENTER):///屏幕中心
????????????x?=?0.5*m_parent->GetGLWindow()->GetSize().x+m_x;
????????????y?=?0.5*m_parent->GetGLWindow()->GetSize().y+m_y;
????????????break;
????????}
????????glWindowPos2d(x,y);
????}
????else
????????glRasterPos3d(m_x,m_y,m_z);

????//調用顯示列表
????glListBase(m_base);
????glCallLists(m_list_len,GL_UNSIGNED_INT,m_lists);
????glPopAttrib();

轉載于:https://www.cnblogs.com/codezhang/archive/2009/06/20/1507320.html

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