fix Collision_ClipTrace_Line_Sphere calculation of impactdist (had a

discussion about this previously but forgot the solution, now reminded)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@11468 d7cf8633-e32d-0410-b094-e92efae38249

diff --git a/collision.c b/collision.c
index ed1fac4e586e1ef07f995eb6e7bb4c1c88c53d6d..f0251fb64a6966675e66cb73f40a1b4d50a508d3 100644 (file)
--- a/collision.c
+++ b/collision.c
@@ -1256,7 +1256,7 @@ void Collision_BrushForBox(colboxbrushf_t *boxbrush, const vec3_t mins, const ve
 // all the results are correct (impactpoint, impactnormal, and fraction)
 float Collision_ClipTrace_Line_Sphere(double *linestart, double *lineend, double *sphereorigin, double sphereradius, double *impactpoint, double *impactnormal)
 {
-       double dir[3], scale, v[3], deviationdist, impactdist, linelength;
+       double dir[3], scale, v[3], deviationdist2, impactdist, linelength;
        // make sure the impactpoint and impactnormal are valid even if there is
        // no collision
        VectorCopy(lineend, impactpoint);
@@ -1278,13 +1278,12 @@ float Collision_ClipTrace_Line_Sphere(double *linestart, double *lineend, double
        // of the line from the sphereorigin (deviation, how off-center it is)
        VectorMA(linestart, impactdist, dir, v);
        VectorSubtract(v, sphereorigin, v);
-       deviationdist = VectorLength2(v);
-       // if outside the radius, it's a miss for sure
-       // (we do this comparison using squared radius to avoid a sqrt)
-       if (deviationdist > sphereradius*sphereradius)
+       deviationdist2 = sphereradius * sphereradius - VectorLength2(v);
+       // if squared offset length is outside the squared sphere radius, miss
+       if (deviationdist2 < 0)
                return 1; // miss (off to the side)
        // nudge back to find the correct impact distance
-       impactdist -= sphereradius - deviationdist/sphereradius;
+       impactdist -= sqrt(deviationdist2);
        if (impactdist >= linelength)
                return 1; // miss (not close enough)
        if (impactdist < 0)