[Plib-users] Intersection Testing / 3ds loading

[Thomas G. <pin...@we...>]

I am writing a game with PLIB it's a kind of 3d jump n run (like "tux a =
quest fo herring"). First I used heightmaps (modified majik-example), =
but now I wanted to use models for my terrain.
I made some models using anim8or and tried to load them. Most of them =
were white, although I applied materials and if i applied textures they =
were stretched over the whole model (but I think that's a problem in =
anim8or). Can I apply states to ssgEntities? How can I modify the =
VtxTables (or whatever the loader uses to store the veritces) of the =
model I loaded?

Problem No. 2:

Intersection Testing. The HOT-Testing works fine, I've always been doing =
it like this:

  invmat[3][0] =3D -ppos.xyz[0] ;
  invmat[3][1] =3D -ppos.xyz[1] ;
  invmat[3][2] =3D  0.0f          ;

  test_vec [0] =3D 0.0f ;
  test_vec [1] =3D 0.0f ;
  test_vec [2] =3D 100000.0f ;

  ssgHit *results ;
  int num_hits =3D ssgHOT ( tscene, test_vec, invmat, &results ) ;

  phits=3Dnum_hits;

  float hot =3D -1000000.0f ;


  for ( i =3D 0 ; i < num_hits ; i++ )
  {
    ssgHit *h =3D &results [ i ] ;

    float hgt =3D - h->plane[3] / h->plane[2] ;

    if ( hgt >=3D hot )
      hot =3D hgt ;
  }

Now (that I have models for the terrain with some walls and steep =
planes) I wanted to use the LOS-intersection testing for checking if I =
am running against a wall.
But it didn't work. I tried it this way:

    sgVec3 test_vec ;
    sgMat4 invmat ;
    sgMakeIdentMat4 ( invmat ) ;

    invmat[3][0] =3D -pos[0] ;
    invmat[3][1] =3D -pos[1] ;
    invmat[3][2] =3D -(pos[2]+1.5) ;

    test_vec [0] =3D 2.0*sin(turn*M_PI/180.0) ;
    test_vec [1] =3D 2.0*cos(turn*M_PI/180.0) ;
    test_vec [2] =3D 1.5 ;

    ssgHit *results ;
    int num_hits =3D ssgIsect ( tscene, sphere, invmat, &results ) ;

    float ehot =3D -1000000.0f ;

    for ( int i =3D 0 ; i < num_hits ; i++ )
    {
      ssgHit *eh =3D &results [ i ] ;

      float ehgt =3D - eh->plane[3] / eh->plane[2] ;

      if ( ehgt >=3D ehot )
        ehot =3D ehgt ;
    }

But it only showed my player's z-distance to the terrain and the normals =
of the polygons I am running on (I guess).
Well, very useful, too, but I wanted to know if my player is running =
against a wall (if the vector test_vec touches a plane).

What do I have to change?

Then I tried the Isect-method with a sphere:

    sgVec3 test_vec ;
    sgMat4 invmat ;
    sgMakeIdentMat4 ( invmat ) ;
    sgSphere *sphere;

    invmat[3][0] =3D -pos[0] ;
    invmat[3][1] =3D -pos[1] ;
    invmat[3][2] =3D -(pos[2]+1.5) ;

    sphere =3D new sgSphere;

    sphere->setCenter(0.0,0.0,1.2);
    sphere->setRadius(1.0);

    ssgHit *results ;
    int num_hits =3D ssgIsect ( tscene, sphere, invmat, &results ) ;

    float ehot =3D -1000000.0f ;

    for ( int i =3D 0 ; i < num_hits ; i++ )
    {
      ssgHit *eh =3D &results [ i ] ;

      float ehgt =3D - eh->plane[3] / eh->plane[2] ;

      if ( ehgt >=3D ehot )
        ehot =3D ehgt ;
    }

The Program crashes when I increase the sphere's radius, and plane[0] =
and plane[1] (A and B in the equation, I guess) change with the =
direction my player is looking in, plane[2 and 3] don't change. But the =
sphere touches neither the ground nor any other part of my scene.

Sorry for the long mail, but I am pretty in despair.

Cheeers, Thomas Gahr