add tabread6c~

svn path=/trunk/externals/nusmuk/; revision=10150

1 files changed, 7 insertions, 5 deletions

diff --git a/tab/tabread4c~.c b/tab/tabread4c~.c
index 41f4ff3..c4a7804 100644
--- a/tab/tabread4c~.c
+++ b/tab/tabread4c~.c
@@ -72,7 +72,7 @@ static t_int *tabread4c_tilde_perform(t_int *w)
     int maxindex;
     t_word *buf = x->x_vec, *wp;
     int i;
-    double a0,a1,a2; // CH
+    double a3,a1,a2; // CH
     
     maxindex = x->x_npoints - 3;
 
@@ -117,10 +117,12 @@ static t_int *tabread4c_tilde_perform(t_int *w)
 //            cminusb - 0.1666667f * (1.-frac) * (
 //                (d - a - 3.0f * cminusb) * frac + (d + 2.0f*a - 3.0f*b)
 // CH
-		a0 = d - c - a + b;
-		a1 = a - b - a0;
-		a2 = c - a;
-		*out++ = ((a0*frac+a1)*frac+a2)*frac+b;       
+	// 4-point, 3rd-order Hermite (x-form)
+	a1 = 0.5f * (c - a);
+	a2 = a - 2.5 * b + 2.f * c - 0.5f * d;
+	a3 = 0.5f * (d - a) + 1.5f * (b - c);
+
+	*out++ =  ((a3 * frac + a2) * frac + a1) * frac + b;     
     }
     return (w+5);
  zero: