add, but don't use, 3 pt inversion interpolation - doesn't work well!

1 files changed, 51 insertions, 2 deletions

diff --git a/device-functions.c b/device-functions.c
index 82d38e6..609208e 100644
--- a/device-functions.c
+++ b/device-functions.c
@@ -2493,6 +2493,35 @@ static int linear_interpolation (int x1, int x2, float y1, float y2, float y_nee
 }
 
 
+static int inverse_3pt_interpolation (int X1, int X2, int X3, float y1, float y2, float y3, float y_need)
+{
+	// assuming y = C + B / (x - A)
+	// A, B, C = constants
+	// x = word
+	// y = output
+
+	// doesn't seem to work well - abandoned
+
+        if ((y1 == y2) || (y2 == y3) || (y1 == y3) || (y_need == 0.0)) {
+                return -1;
+        }
+
+	float x1 = (float) X1;
+	float x2 = (float) X2;
+	float x3 = (float) X3;
+
+	float A = (x1*x2*y1 - x1*x2*y2 - x1*x3*y1 + x1*x3*y3 + x2*x3*y2 - x2*x3*y3) /
+		  (-x1*y2 + x1*y3 + x2*y1 - x2*y3 - x3*y1 + x3*y2);
+
+	float B = (y1 - y2) / ((1 / (x1 - A)) - (1 / (x2 - A)));
+
+	float C = y1 - B / (x1 - A);
+
+	float solved = A + B / (y_need - C);
+	return (int) solved;
+}
+
+
 static int inverse_interpolation (int x1, int x2, float y1, float y2, float y_need)
 {
 	// assuming y = B / (x - A)
@@ -2507,7 +2536,11 @@ static int inverse_interpolation (int x1, int x2, float y1, float y2, float y_ne
 	float A = ((y1 * x1) - (y2 * x2)) / (y1 - y2);
 	float B = y1 * (x1 - A);
 
-	return (int) (A + (B / y_need));
+	int solved = (int) (A + (B / y_need));
+
+//	printf ("x1 %d, x2 %d, y1 %e, y2 %e, solved %d for %e\n",x1,x2,y1,y2,solved,y_need);
+
+	return (int) solved;
 }
 
 
@@ -2823,7 +2856,11 @@ int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int
 				// we copy these floats out into variables because anything that touches
 				// floats seems to generate instructions that can't work on unaligned
 				// data and these are unaligned.
-				float pwlamp1, pwlamp2;
+				float pwlamp0, pwlamp1, pwlamp2;
+
+//				if (index>0) {
+//					memcpy(&pwlamp0, &pwl_amp[index-1], sizeof(pwlamp0));
+//				}
 				memcpy(&pwlamp1, &pwl_amp[index], sizeof(pwlamp1));
 				memcpy(&pwlamp2, &pwl_amp[index+1], sizeof(pwlamp2));
 
@@ -2886,6 +2923,13 @@ int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int
 
 					if (reciprocal_relationship) {
 						*word_out = inverse_interpolation (pwl_vc[index], pwl_vc[index+1], pwlamp1, pwlamp2, tweaked_use_ampl);
+
+//						if (index>0) {
+//							int test_word_out = inverse_3pt_interpolation (pwl_vc[index-1], pwl_vc[index], pwl_vc[index+1], pwlamp0, pwlamp1, pwlamp2, tweaked_use_ampl);
+//							printf ("%d %d\n",*word_out,test_word_out);
+//							*word_out = test_word_out;
+//						}
+
 					} else {
 						*word_out = linear_interpolation (pwl_vc[index], pwl_vc[index+1], pwlamp1, pwlamp2, tweaked_use_ampl);
 					}
@@ -2938,6 +2982,11 @@ int Set_VI_Control(int parameter,int channel,float new_ampl,int *point_found,int
 				*entry=entry_i;
 
 				*word_out = inverse_interpolation (pwl_vc[index], pwl_vc[index+1], pwl_amp[index], pwl_amp[index+1], tweaked_use_ampl);
+//				if (index>0) {
+//					int test_word_out = inverse_3pt_interpolation (pwl_vc[index-1], pwl_vc[index], pwl_vc[index+1], pwl_amp[index-1], pwl_amp[index], pwl_amp[index+1], tweaked_use_ampl);
+//					printf ("ext %d %d\n",*word_out,test_word_out);
+//					*word_out = test_word_out;
+//				}
 			}
 		}
 	}