How to draw 2D & 3D stuffs in OpenGL together? If p开发者_Go百科ossible, please show me some C++ code. Please show both how to draw behind & in front of 3D objects.
About that way:
void render_perspective_scene(void);
void render_ortho_scene(void);
void render_HUD();
void display()
{
float const aspect = (float)win_width/(float)win_height;
glViewport(0,0,win_width,win_height);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-aspect*near/lens, aspect*near/lens, -near/lens, near/lens, near, far);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
render_perspective_scene();
// just clear the depth buffer, so that everything that's
// drawn next will overlay the previously rendered scene.
glClear(GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-aspect*scale, aspect*scale, -scale, scale, 0, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
render_ortho_scene();
// Same for the HUD, only that we render
// that one in pixel coordinates.
glClear(GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, win_width, 0, win_height, 0, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
render_HUD();
}
You are on the right track but you must also disable depth testing when drawing your 2d-graphics: glDisable(GL_DEPTH_TEST);
Otherwise it might become hidden by your 3d-graphics.
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