drawing border around viewports

OpenGL OpenGL: Basic Coding
1

Hi, I am trying to display 4 different viewports in a window and I want to use a dark line to separate them. Can anyone help? thanks

2

You can draw lines by passing GL_LINES, GL_LINE_STRIP or GL_LINE_LOOP to glBegin. With a clever modelview and projection matrix, you can draw the lines in screen space coordinates, like this.

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-0.5, window_width-0.5, -0.5, window_height-0.5, -1, 1);
glBegin(GL_LINE_LOOP);
...

Now you can draw the lines in screen space coordinates, and then you just set the viewports and render them as you like.