opengl - 如何将片段着色器应用于每个像素？

Question

我将一些透明贴花渲染到单独的帧缓冲区中。现在我正在尝试将此缓冲区与后台缓冲区（活动目标）混合。

我假设我必须将 fbo 的颜色缓冲区作为纹理加载到片段着色器中，并将纹理颜色输出到活动目标。如何告诉显卡为每个像素执行此操作？

Answer 1

绘制一个覆盖整个屏幕的四边形或两个三角形。

Answer 2

my code for the fullscreen rectangle/quad this is old method - from OpenGL 1.1, but works :) For new OpenGL 3.* you have to use VBO/Arrays

glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();

glBegin(GL_QUADS);
glTexCoord2f( 0,0 );
glVertex3d( -1.0,-1.0, 0 );
glTexCoord2f( 1,0 );
glVertex3d(  1.0,-1.0, 0 );
glTexCoord2f( 1,1 );
glVertex3d(  1.0, 1.0, 0 );
glTexCoord2f( 0,1 );
glVertex3d( -1.0, 1.0, 0 );
glEnd();

glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glPopMatrix();

of course you have to setup textures before