[gameprogrammer] Re: flight simulation camera
- From: "richard sabbarton" <richard.sabbarton@xxxxxxxxx>
- To: "Julien Breton" <julienbreton@xxxxxxxxxx>, gameprogrammer@xxxxxxxxxxxxx
- Date: Fri, 28 Sep 2007 09:59:33 +0100
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 --'
> >
> > ---------------------
> > To unsubscribe go to http://gameprogrammer.com/mailinglist.html
> >
> >
>
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