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Ground collision detection optimizations contributed by Norman Vine.

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curt 1998-07-16 17:34:24 +00:00
parent 8a7fc0d34e
commit 5ed5107fc1
1 changed files with 58 additions and 19 deletions
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77
Scenery/tile.cxx
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@ -29,6 +29,14 @@
#include "tile.hxx"
// return the sign of a value
#define FG_SIGN( x ) ((x) >= 0 ? 1 : -1)
// return min or max of two values
#define FG_MIN(A,B) ((A) < (B) ? (A) : (B))
#define FG_MAX(A,B) ((A) > (B) ? (A) : (B))
// Constructor
fgFRAGMENT::fgFRAGMENT ( void ) {
}
@ -46,6 +54,7 @@ void fgFRAGMENT::add_face(int n1, int n2, int n3) {
}
/*
// return the sign of a value
static int fg_sign( double x ) {
if ( x >= 0 ) {
@ -76,6 +85,21 @@ static double fg_max( double a, double b, double c ) {
return(result);
}
*/
// return the minimum of the three values
static double fg_min3 (double a, double b, double c)
{
return (a > b ? FG_MIN (b, c) : FG_MIN (a, c));
}
// return the maximum of the three values
static double fg_max3 (double a, double b, double c)
{
return (a < b ? FG_MAX (b, c) : FG_MAX (a, c));
}
// test if line intesects with this fragment. p0 and p1 are the two
@ -151,20 +175,26 @@ int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
y0 = end0->y; y1 = end1->y;
z0 = end0->z; z1 = end1->z;
a1 = x1 - x0;
if ( fabs(x1 - x0) > FG_EPSILON ) {
a1 = 1.0 / (x1 - x0);
} else {
// we got a big divide by zero problem here
a1 = 0.0;
}
b1 = y1 - y0;
c1 = z1 - z0;
// intersect the specified line with this plane
t1 = b * b1 / a1;
t2 = c * c1 / a1;
t1 = b * b1 * a1;
t2 = c * c1 * a1;
// printf("a = %.2f t1 = %.2f t2 = %.2f\n", a, t1, t2);
if ( fabs(a + t1 + t2) > FG_EPSILON ) {
result->x = (t1*x0 - b*y0 + t2*x0 - c*z0 + d) / (a + t1 + t2);
result->y = (b1/a1) * (result->x - x0) + y0;
result->z = (c1/a1) * (result->x - x0) + z0;
t3 = a1 * (result->x - x0);
result->y = b1 * t3 + y0;
result->z = c1 * t3 + z0;
// printf("result(d) = %.2f\n",
// a * result->x + b * result->y + c * result->z);
} else {
@ -187,7 +217,9 @@ int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
// as any
return(1);
}
if ( fg_sign(t1 - t2) == fg_sign(t1 - t3) ) {
side1 = FG_SIGN (t1 - t2);
side2 = FG_SIGN (t1 - t3);
if ( side1 == side2 ) {
// same side, punt
continue;
}
@ -195,12 +227,12 @@ int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
// check to see if intersection point is in the bounding
// cube of the face
xmin = fg_min(p1[0], p2[0], p3[0]);
xmax = fg_max(p1[0], p2[0], p3[0]);
ymin = fg_min(p1[1], p2[1], p3[1]);
ymax = fg_max(p1[1], p2[1], p3[1]);
zmin = fg_min(p1[2], p2[2], p3[2]);
zmax = fg_max(p1[2], p2[2], p3[2]);
xmin = fg_min3 (p1[0], p2[0], p3[0]);
xmax = fg_max3 (p1[0], p2[0], p3[0]);
ymin = fg_min3 (p1[1], p2[1], p3[1]);
ymax = fg_max3 (p1[1], p2[1], p3[1]);
zmin = fg_min3 (p1[2], p2[2], p3[2]);
zmax = fg_max3 (p1[2], p2[2], p3[2]);
// printf("bounding cube = %.2f,%.2f,%.2f %.2f,%.2f,%.2f\n",
// xmin, ymin, zmin, xmax, ymax, zmax);
// punt if outside bouding cube
@ -226,7 +258,7 @@ int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
dx = xmax - xmin;
dy = ymax - ymin;
dz = zmax - zmin;
min_dim = fg_min(dx, dy, dz);
min_dim = fg_min3 (dx, dy, dz);
if ( fabs(min_dim - dx) <= FG_EPSILON ) {
// x is the smallest dimension
x1 = p1[1]; y1 = p1[2];
@ -245,27 +277,31 @@ int fgFRAGMENT::intersect( fgPoint3d *end0, fgPoint3d *end1, int side_flag,
x2 = p2[0]; y2 = p2[1];
x3 = p3[0]; y3 = p3[1];
rx = result->x; ry = result->y;
} else {
// all dimensions are really small so lets call it close
// enough and return a successful match
return(1);
}
// check if intersection point is on the same side of p1 <-> p2 as p3
side1 = fg_sign((y1 - y2) * ((x3) - x2) / (x1 - x2) + y2 - (y3));
side2 = fg_sign((y1 - y2) * ((rx) - x2) / (x1 - x2) + y2 - (ry));
side1 = FG_SIGN ((y1 - y2) * ((x3) - x2) / (x1 - x2) + y2 - (y3));
side2 = FG_SIGN ((y1 - y2) * ((rx) - x2) / (x1 - x2) + y2 - (ry));
if ( side1 != side2 ) {
// printf("failed side 1 check\n");
continue;
}
// check if intersection point is on correct side of p2 <-> p3 as p1
side1 = fg_sign((y2 - y3) * ((x1) - x3) / (x2 - x3) + y3 - (y1));
side2 = fg_sign((y2 - y3) * ((rx) - x3) / (x2 - x3) + y3 - (ry));
side1 = FG_SIGN ((y2 - y3) * ((x1) - x3) / (x2 - x3) + y3 - (y1));
side2 = FG_SIGN ((y2 - y3) * ((rx) - x3) / (x2 - x3) + y3 - (ry));
if ( side1 != side2 ) {
// printf("failed side 2 check\n");
continue;
}
// check if intersection point is on correct side of p1 <-> p3 as p2
side1 = fg_sign((y1 - y3) * ((x2) - x3) / (x1 - x3) + y3 - (y2));
side2 = fg_sign((y1 - y3) * ((rx) - x3) / (x1 - x3) + y3 - (ry));
side1 = FG_SIGN ((y1 - y3) * ((x2) - x3) / (x1 - x3) + y3 - (y2));
side2 = FG_SIGN ((y1 - y3) * ((rx) - x3) / (x1 - x3) + y3 - (ry));
if ( side1 != side2 ) {
// printf("failed side 3 check\n");
continue;
@ -309,6 +345,9 @@ fgTILE::~fgTILE ( void ) {
// $Log$
// Revision 1.3 1998/07/16 17:34:24 curt
// Ground collision detection optimizations contributed by Norman Vine.
//
// Revision 1.2 1998/07/12 03:18:28 curt
// Added ground collision detection. This involved:
// - saving the entire vertex list for each tile with the tile records.