[gameprogrammer] Re: flight simulation camera
- From: Julien Breton <julienbreton@xxxxxxxxxx>
- To: <gameprogrammer@xxxxxxxxxxxxx>
- Date: Mon, 1 Oct 2007 10:13:07 +0200
Hi Richard,
When I turrn the plane around the Y axe in global coordinates the plane turns
on his Y axe in the same time. Now with your function the camera turns around Y
with the plane in the plane coordinates.
I have just a little problem because the camera looks always straight (the
camera doesn't turn on her Y axe) but I think it's not a big problem.
thanks for your help,
Julien
Date: Fri, 28 Sep 2007 09:59:33 +0100
From: richard.sabbarton@xxxxxxxxx
To: julienbreton@xxxxxxxxxx; gameprogrammer@xxxxxxxxxxxxx
Subject: [gameprogrammer] Re: flight simulation camera
Hi Julien,
It is assumed that you already know your rotation. This, in your case would be
the position/rotation of the plane. So, assume your Plane is at plX,plY,plZ
and is rotated by prX, prY, prZ.
Your camera position would be behind the plane so plX, plY - CameraDistance,
plZ. You would have an offset camera position of 0,CameraDistance,0.
So of you had a point class with the RotatePoint() function you could use...
CMyPoint CameraOffset;
CameraOffset.x = 0;
CameraOffset.y = -5; (distance of camera)
CameraOffset.z = 0;
CameraOffset.RotatePoint(prX,prY,prZ);
This would take your camera offset and rotate it around Zero... You can then
move your camera to that point which would be
CameraOffset.xRotated + plX , CameraOffset.yRotated + plY ,
CameraOffset.zRotated + plZ
This is the actual position of the camera to place it behind the plan. You
then need to rotate the camera at the same angle as your plane using whatever
code you are using now.
Regards
Richard
On 28/09/2007, Julien Breton <julienbreton@xxxxxxxxxx> wrote:
Hello,
Thanks for your code,
I have a question,
When you have calculate xRotated, yRotated and zRotate give you the values to
glRotatef function ? (ex : glRotatef (xRotated, 1.0, 0.0, 0.0)), may be I can
use gluLookAt?
Thanks,
Julien.
Date: Thu, 27 Sep 2007 11:07:06 +0100
From: richard.sabbarton@xxxxxxxxx
To: gameprogrammer@xxxxxxxxxxxxx
Subject: [gameprogrammer] Re: flight simulation camera
Hi There,
I had exactly the same problem recently because I was making some calculations
in the wrong order. The problem was with the glTranslate and glRotate. I tend
to rotate the world around the camera rather than the camera around the world.
So I will first do a glTranslate/rotate to move to the point you want to draw
your plane. Then do a glPushMatrix() and render the rest of your scene. Once
the rest of your scene is drawn then you can do glPopMatrix() and then render
the plane. It should always be right where you want it to be.
I am just a beginner really. But this is how I would do this. There are
probably better ways.
The problem I ran into was the start point of ammo when firing. I wanted my
bullets to appear to fire from underneath you but, when looking down, they
started right in front of you. And when looking up you couldn't see them all.
Sounds like a similar issue. The problem is that you know the angle of your
plane and you know the distance behind it that you want to move but what you
need calculate is the x,y,z of the camera. In the same way I needed to
calculate the x,y,z of my ammo start point. I wrote the following code to
rotate a 3D point as part of a 3D point class I was working on.
// x,y,z are members of a 3D Point Class as are xRotated
// yRotated and zRotated. We use the rotated points for
// rendering but we leave the original x,y,z unchanged
// to avoid any distortion.
RotatePoint(int DegAroundX, int DegAroundY, int DegAroundZ){
// Define some variables needed to perform the rotation
FLOAT oldx,oldy,oldz,newx,newy,newz,alpha; // We need to use FLOAT
values for accuracy
oldx = x;
oldy = y;
oldz = z;
// ROTATE AROUND Y FIRST;
alpha = (FLOAT)DegAroundY / (FLOAT)57.29578; // We have to divide
Degrees by 57.29578
// to convert to radians
newx = cos(alpha)*oldx - sin(alpha)*oldz;
newy = oldy;
newz = sin(alpha)*oldx + cos(alpha)*oldz;
oldx = newx; // After each rotation we have to ensure
oldy = newy; // that the new values are pushed into the
oldz = newz; // old values because otherwise we will be
// rotating partially rotated values.
// Then Around X;
alpha = (FLOAT)DegAroundX / (FLOAT)57.29578;
newz = cos(alpha)*oldz - sin(alpha)*oldy;
newy = sin(alpha)*oldz + cos(alpha)*oldy;
newx = oldx;
oldx = newx;
oldy = newy;
oldz = newz;
// Then Around Z;
alpha = (FLOAT)DegAroundZ / (FLOAT)57.29578;
newx = cos(alpha)*oldx - sin(alpha)*oldy;
newy = sin(alpha)*oldx + cos(alpha)*oldy;
newz = oldz;
xRotated = newx;
yRotated = newy;
zRotated = newz;
}
I apologise for the minimal comments. cos, sin & tan were giving me a headache
by the time I was done. I started putting a repository of notes and stuff on
my website. You can take a look at it here.
http://www.fullonsoftware.co.uk/main.html. I put them in my Snippets section.
Lots of my beginners stuff about openGL and C++. Plus some screenshots of my
(now stalled) most recent project.
Regards
Richard
On 27/09/2007, Julien Breton <julienbreton@xxxxxxxxxx> wrote:
Thanks for your answer,
My probleme is that my camera don't stay locked to the plane. When I start my
exe the camera is behind the plane but when I turn the plane around the Y axe
(in global coordinates) the camera moves but don't stay behind the plane. I can
always see the plane but on the right (or left) and front at the end but I want
stay behind the plane.
It's not easy to explain and sorry for my English.
I use C++/OpenGL
Julien
> From: david@xxxxxxxxxxx
> To: gameprogrammer@xxxxxxxxxxxxx
> Subject: [gameprogrammer] Re: flight simulation camera
> Date: Thu, 27 Sep 2007 09:40:31 +0200
>
> On Thursday 27 September 2007, Julien Breton wrote:
> >
> > Hello,
> >
> > Do you know where I can find an example of a flight simulation
> > camera ?
>
> What do you mean, exactly?
>
> From what I've seen, the basic logic of how the camera works in
> simulators (flight, racing etc) is that it's simply locked to the
> vehicle, ie it sits where the pilot/driver would be, looking straight
> ahead.
>
> In racing simulators, it's common to add minor adjustments to the
> position and view angle of the camera, to hint about the G-forces
> that are "lost in transmission". (Lost, unless you're using a moving
> platform, that is.) I suppose you could do that in a flight simulator
> too, but I can't remember seeing that. X-Plane has a different
> solution: Blackout and redout is simulated by fading the view to
> black and red respectively. Simple and effective. (Not very not
> relevant to racing though, as you'd normally never get that kind of
> G-forces on the vertical axis in a car for extended periods of time.)
>
>
> //David Olofson - Programmer, Composer, Open Source Advocate
>
> .------- http://olofson.net
- Games, SDL examples -------.
> | http://zeespace.net - 2.5D rendering engine |
> |
http://audiality.org - Music/audio engine |
> | http://eel.olofson.net - Real time scripting |
> '--
http://www.reologica.se - Rheology instrumentation --'
>
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