sky rendering

[joevenzon]

It sounds like you understand it pretty well but I'll step through the code and explain it bit by bit anyway:

Code:

glPushMatrix();

This just tells OpenGL to remember the current transform matrix because we're going to want to return it to this state later on.

Code:

double temp_matrix[16];
game.cam.PutTransformInto(temp_matrix);
glLoadMatrixd(temp_matrix);

This LoadMatrix call overwrites the current transform matrix with the camera rotation (but not the camera translation).

Code:

if (game.track.GetVerticalTrackingSkyboxes())
{
     glTranslatef(0,game.cam.position.y,0);
}

If the IF is true, this adds (to the current transform) a translation up by the camera height.

Code:

glMultMatrixf(i->GetMatrix4()->data);

This adds (to the current transform) the object's transform, which is a 90 degree rotation to get the object coordinates and the opengl coordinates to line up and a translation by the object coordinates.

The upshot of all of this is that for skybox objects the scene is set up so that the camera is put at the center of the scene (0,0,0), the camera is rotated properly, if vertical skybox is true it's moved upward to its height, and the object is placed at whatever coordinates it was modeled at.

Now, as for your change to doing

Code:

glTranslatef(-objpos.x,-objpos.y,-objpos.z);

This would mean that the scene would be set up so that the camera is put at the center of the scene (0,0,0), the camera is rotated properly, and if vertical skybox is true the *center of the object* is placed at the center of the scene (0,0,0) or if it's false the object is placed at whatever coordinates it was modeled at.

It's important to note that the i->GetDraw()->object_center variable is the *calculated center* of the object's mesh, so for example if the object's mesh starts at 0 height and goes to 50, the object_center would be 25.

Anyway, if you're okay with using this translation I'll make the change and check it in (even if it does make "vertical tracking" a bit of a misnomer).