[Plib-users] Help for code that is not documented and is confusing

[Dimitris M. <dm...@ya...>]

Hello people, I am trying to study plib and do some tricks with it, I found=
 code for doing things. No dicent documentation though. So everything I tri=
ed I did it blindly....=0ACan some one help me with the code snippets below=
 ?=0A=0AFIRST :=0A=0A    /* Look for the nearest polygon *beneath* my_posit=
ion */=0A    float HOT_TOLERANCE =3D 1.0f;=0A    ssgHit *results;=0A    int=
 num_hits;=0A    float hot;  /* H.O.T =3D=3D Height Of Terrain */=0A    sgV=
ec3 HOTvec;=0A    sgMat4 invmat;=0A    sgMakeIdentMat4( invmat );=0A    inv=
mat[3][0] =3D - my_position[0];=0A    invmat[3][1] =3D - my_position[1];=0A=
    invmat[3][2] =3D 0.0f;=0A=0A    sgSetVec3( HOTvec, 0.0f, 0.0f, -my_posi=
tion[2] + HOT_TOLERANCE );//FIXME I don't know why I use minus here!!=0A   =
 num_hits =3D ssgHOT( scene, HOTvec, invmat, &results );=0A    hot =3D DEEP=
EST_HELL;=0A    for ( int i =3D 0; i < num_hits; i++ ) {=0A        ssgHit *=
h =3D &results[i];=0A        float hgt =3D - h->plane[3] / h->plane[2];=0A =
       if ( hgt >=3D hot ) {=0A            hot =3D hgt;=0A            if ( =
normal !=3D NULL )=0A                sgCopyVec3( normal, h->plane );=0A    =
    }=0A    }=0A    return hot;=0A}=0A=0ABesides the fact that I took as "g=
lobal constant" the code, I didn;t understand why the inverse matrix! ?=0AW=
hat is supposed to do ?=0A=0Alower You see a FIXME, it is mine, and yes wha=
t does this line do ?=0AIf I have a 3000polygon coming against 5000 polygon=
s of another surface, the for loop, goes all this around to seek the collit=
ion?=0AWhat is, really ssgHit, and the division with float hgt ?=0A=0ANext =
I want to ask about the code in PPE about picking...To tell you the truth I=
 read OpenGL book about glLoadName* but I don't see how that would fit here=
 when I load a model and not drawing vertices....=0AHas anyone tried to dra=
w something in 3D from his mouse click? e.g. the ray and try to intercect w=
ith the objects in the scenery?=0AOR has anyone achieved to point and click=
 an object ? I haven't seen code to do that from plib...apart ppe, which pp=
e neither compiles nor has some remarks to understand it's stuff...=0A=0ACr=
ying for help...=0ADimitris=0A=0AThank you=0A=0A=0A=0A=0A       =0A________=
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