某些多边形模式下OpenGL背景消失

问题描述

我通过绘制四边形来创建简单的渐变背景，如下所示:

I am creating a simple gradient background by drawing a quad as follows:

 glMatrixMode GL.GL_PROJECTION
 glLoadIdentity

 glMatrixMode GL.GL_MODELVIEW
 glLoadIdentity

 ***glPolygonMode GL_FRONT_AND_BACK, GL_LINE***

 glDisable glcDepthTest

   glBegin bmQuads

     glColor4d 1, 0, 0, 1

     glVertex2i -1, -1
     glVertex2i 1, -1

     glColor4d 0, 0, 1, 1

     glVertex2i 1, 1
     glVertex2i -1, 1

    GL.glEnd

  GL.glEnable glcDepthTest

然后，我设置我的查看矩阵并绘制我的3D场景.当(场景的)多边形模式设置为GL_FILL时，这可以按预期工作，但是当我(场景的)多边形模式设置为GL_LINE或GL_POINT时，背景四边形消失，并且背景绘制为 glClearColor .

I then set up my viewing matrices and draw my 3D scene. This works as expected when the polygon mode (of the scene) is set to GL_FILL, but when I set the polygon mode (of the scene) to GL_LINE or GL_POINT, the background quad disappears and the background is drawn as the color specified in glClearColor.

我尝试了几种不同的混合选项(包括完全禁用它)，所以我认为问题不在于混合模式.

I have tried several different blending options (including disabling it altogether), so I don't think the problem is blend mode related.

将以下多边形模式添加到上述代码中即可解决此问题！

Adding the following polygon mode to above code solves this issue!

glPolygonMode GL_FRONT_AND_BACK，GL_LINE

推荐答案

在绘制背景多边形之前，您需要将GL_FILL的多边形模式压入堆栈，然后将其从堆栈中弹出.

You need to push the polygon mode of GL_FILL onto the stack before drawing your background polygon, then pop it back off the stack.

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