SimpleCameraLoop Actionscript

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RCSfile: SimpleCameraLoop.as,v  Revision: 1.3  Date: 2003/01/29 16:40:19  

Copyright 2003 Orgdot AS. All Rights Reserved. http://dev.swfit.com
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
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A simple interactive camera model - based on projection (rotation and scale) of flash movie clips. Rules: The camera back wall is circular and always perpendicular to the focal point. The centers of the movie clips are projected through the focal point. For ease of computation / orientation we let the clips exist on the same side of the focal point as the camera back wall.
The unrotated xy-coordinates are determined from where they hit the camera wall, and then rotated. If they do not hit the camera back wall, they are set invisible. The distance from the focal point determines the scale (and / or alpha) of the movie clips. The rotation of the movie clips is the opposite of the camera. See MouseEngineLoop for details on camera x, y, z, rotation etc.
author      Olaf Havnes
version     Revision: 1.3  Date: 2003/01/29 16:40:19  
since       SWFIT1.0


To start with we have a vector in space Pn = (xp, yp, zp) and a vector C (stored in _level0) representing the normal of the camera back wall.


Get the squared length.

p_len_sq = xp * xp + yp * yp + zp * zp;

The change should not be so dramatic as to make this very wrong

NB! Remember to supply an initial p_len!


p_len = (p_len + p_len_sq / p_len) / 2;

Compute the dot product :

p_dot_c = xp * /:camera_x + yp * /:camera_y + zp * /:camera_z;


Is the particle on the correct side of the focal point?

if (p_dot_c > 0)
{

intersection test: cos (A) > cos (Amax), and p_dot_c = |C| * |P| * cos (A)

we have stored some precomputed values at _level0:

   if (p_dot_c * p_dot_c > p_len_sq * /:cisect)
   {

show this clip

       _visible = true;
       

to find the intersection point we scale the vector P:

Pt = t * P, so that Pt touches the back wall. Then (Pt - C).C = 0,

or t = C.C / P.C = |C|^2 / P.C

       t = /:cam_len_sq / p_dot_c;
       
       x_tp = t * xp - /:camera_x;
       y_tp = t * yp - /:camera_y;
       z_tp = t * zp - /:camera_z;

project this vector onto the "rotated horizon unit vector" of the camera back wall

       xd = x_tp * /:huv_x + y_tp * /:huv_y + z_tp * /:huv_z;

project this vector onto the "rotated verizon unit vector" of the camera back wall

       yd = x_tp * /:vuv_x + y_tp * /:vuv_y + z_tp * /:vuv_z;
   }
   else
   {
       _visible = false;
   }
}
else
{

kill the particle ?

   reset = true;
}