View Full Version : glTrue3dCoordinates ?

06-03-2005, 05:46 PM
Hello All,

I have an object that have 4 vertices.

I can rotate it, translate it, etc. with glTranslate, glRotate inside the push and pop.

The only thing I want is to know where, in my 3d world, this object is renderized.

I mean: the 3d world coordinates of the 4 vertices.

I can translate it for any 3d coordinate but its 4 vertices remains with the original x,y,z coordinates.

Is there any command I am missing and can give
the holy 3d-world coordinates I need ?

In my program besides the display of the objects I put the display of the coordinatees of the object and they are all the same (no changing), even when my object is flying around and rotating ...

I need this to create vectors to my Pilot eye.
Any Help ?

Any glTrue3dCoordinates ?


Ehsan Kamrani
06-03-2005, 06:05 PM
The order of transformation is too important.Assume that you are start with the function glLoadIdentity().If you first use from the glVertex*()s to construct your object and then transform the modelview matrix, you can't rotate, translate or scale your object.In this case you are using from the *original*coordinate system-glLoadIdentity()-to specify your vertices.
Actually, the glVertex*() is measued from the current coordinate system. So if you first transform your modelview matrix-Your coordinate system-and then write your glVertex*() functions, you are using from the *transformed* coordinate system to specify your vertices.In this case, transformations can change the position of the vertices.

06-03-2005, 06:44 PM
Thanks Ehsan.

I will try this.

In fact I am doing a flight sim and the Pilot View is hard to implement.
Iīve created a simple object with 4 vertices that represent the PilotEye, the Front view,
the right viewe and the Up. I put this object in the same coordinates of the planed cg
and so I could use the vertices to create the vectors and create the pilot view for the camera
but that damn thing is happening.
The plane yaw, pitch, roll, all ok but its coordinates are tied to some thing

three days in the same horrible thing.

Itīs terrible losting lots of days implementing a flight model and cannot implement a simple
Pilot View ....

Well, I will try.

Thanks again