fix 'overlapping/intersecting triangles' issue, patch by Christian Borss.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=649891

We are using a speaker setup which includes, among others, a "front left",
"front right", "center", "top center", and a "floor center" speaker. We
observed that a sound source panned slightly right beside the "center" is
almost solely played back via the "center" while a sound source panned slightly
left beside the "center" is played back by the "front left", the "top center",
and the "floor center" speaker. This has the effect that the auditory source-
width jumps, if we move the panned sound source from right to left. The reason
is as follows: for the measured azimuth/elevation angles of our speaker
positions (e.g., 3 elevated center speakers at 2°, 2°, and 3° azimuth
angle), define_loudspeakers() returns intersecting triangles. The attached
patch solves this issue.



svn path=/trunk/externals/vbap/; revision=15871

1 files changed, 10 insertions, 8 deletions

diff --git a/define_loudspeakers.c b/define_loudspeakers.c
index 7ec06f8..5c7e478 100644
--- a/define_loudspeakers.c
+++ b/define_loudspeakers.c
@@ -546,6 +546,8 @@ static int lines_intersect(int i,int j,int k,int l,t_ls  lss[MAX_LS_AMOUNT])
   //t_float angle;
   t_float dist_ij,dist_kl,dist_iv3,dist_jv3,dist_inv3,dist_jnv3;
   t_float dist_kv3,dist_lv3,dist_knv3,dist_lnv3;
+  // TODO epsilon needs to be updated for 64-bit/double precision
+  t_float epsilon = 1e-9;
 
   ls_cross_prod(lss[i],lss[j],&v1);
   ls_cross_prod(lss[k],lss[l],&v2);
@@ -567,17 +569,17 @@ static int lines_intersect(int i,int j,int k,int l,t_ls  lss[MAX_LS_AMOUNT])
   dist_lnv3 = (vec_angle(neg_v3,lss[l]));
 
   /* if one of loudspeakers is close to crossing point, don't do anything*/
-  if(fabsf(dist_iv3) <= 0.01 || fabsf(dist_jv3) <= 0.01 || 
-		 fabsf(dist_kv3) <= 0.01 || fabsf(dist_lv3) <= 0.01 ||
-     fabsf(dist_inv3) <= 0.01 || fabsf(dist_jnv3) <= 0.01 || 
-     fabsf(dist_knv3) <= 0.01 || fabsf(dist_lnv3) <= 0.01 )
+  if(fabsf(dist_iv3)  <= epsilon || fabsf(dist_jv3)  <= epsilon || 
+     fabsf(dist_kv3)  <= epsilon || fabsf(dist_lv3)  <= epsilon ||
+     fabsf(dist_inv3) <= epsilon || fabsf(dist_jnv3) <= epsilon || 
+     fabsf(dist_knv3) <= epsilon || fabsf(dist_lnv3) <= epsilon )
     return(0);
 
   // if crossing point is on line between both loudspeakers return 1
-  if (((fabsf(dist_ij - (dist_iv3 + dist_jv3)) <= 0.01 ) &&
-       (fabsf(dist_kl - (dist_kv3 + dist_lv3))  <= 0.01)) ||
-      ((fabsf(dist_ij - (dist_inv3 + dist_jnv3)) <= 0.01)  &&
-       (fabsf(dist_kl - (dist_knv3 + dist_lnv3)) <= 0.01 ))) {
+  if (((fabsf(dist_ij - (dist_iv3 + dist_jv3))   <= epsilon)  &&
+       (fabsf(dist_kl - (dist_kv3 + dist_lv3))   <= epsilon)) ||
+      ((fabsf(dist_ij - (dist_inv3 + dist_jnv3)) <= epsilon)  &&
+       (fabsf(dist_kl - (dist_knv3 + dist_lnv3)) <= epsilon))) {
     return (1);
   } else {
     return (0);