F-Curve Modifiers: Experimental 'Additive' option for Generator Modifiers

This setting means that instead of blindly replacing the existing values, the generator modifier will instead apply its effects on top of any existing modifiers (and/or curve data). 
Thus, it is now possible to apply effects such sin/cos-based oscillations on top of keyframed motion. 

1 files changed, 37 insertions, 14 deletions

diff --git a/source/blender/blenkernel/intern/fcurve.c b/source/blender/blenkernel/intern/fcurve.c
index f087727dd9c..90e40dd50fb 100644
--- a/source/blender/blenkernel/intern/fcurve.c
+++ b/source/blender/blenkernel/intern/fcurve.c
@@ -1277,8 +1277,12 @@ static void fcm_generator_evaluate (FCurve *fcu, FModifier *fcm, float *cvalue,
 				value += data->coefficients[i] * powers[i];
 			
 			/* only if something changed, write *cvalue in one go */
-			if (data->poly_order)
-				*cvalue= value;
+			if (data->poly_order) {
+				if (data->flag & FCM_GENERATOR_ADDITIVE)
+					*cvalue += value;
+				else
+					*cvalue= value;
+			}
 				
 			/* cleanup */
 			if (powers) 
@@ -1296,8 +1300,12 @@ static void fcm_generator_evaluate (FCurve *fcu, FModifier *fcm, float *cvalue,
 				value *= (cp[0]*evaltime + cp[1]);
 				
 			/* only if something changed, write *cvalue in one go */
-			if (data->poly_order)
-				*cvalue= value;
+			if (data->poly_order) {
+				if (data->flag & FCM_GENERATOR_ADDITIVE)
+					*cvalue += value;
+				else
+					*cvalue= value;
+			}
 		}
 			break;
 			
@@ -1323,8 +1331,10 @@ static void fcm_generator_evaluate (FCurve *fcu, FModifier *fcm, float *cvalue,
 				case FCM_GENERATOR_FN_TAN: /* tangent wave */
 				{
 					/* check that argument is not on one of the discontinuities (i.e. 90deg, 270 deg, etc) */
-					if IS_EQ(fmod((arg - M_PI_2), M_PI), 0.0)
-						*cvalue= 0.0f; /* no value possible here */
+					if IS_EQ(fmod((arg - M_PI_2), M_PI), 0.0) {
+						if ((data->flag & FCM_GENERATOR_ADDITIVE) == 0)
+							*cvalue = 0.0f; /* no value possible here */
+					}
 					else
 						fn= tan;
 				}
@@ -1332,19 +1342,25 @@ static void fcm_generator_evaluate (FCurve *fcu, FModifier *fcm, float *cvalue,
 				case FCM_GENERATOR_FN_LN: /* natural log */
 				{
 					/* check that value is greater than 1? */
-					if (arg > 1.0f)
+					if (arg > 1.0f) {
 						fn= log;
-					else
-						*cvalue= 0.0f; /* no value possible here */
+					}
+					else {
+						if ((data->flag & FCM_GENERATOR_ADDITIVE) == 0)
+							*cvalue = 0.0f; /* no value possible here */
+					}
 				}
 					break;
 				case FCM_GENERATOR_FN_SQRT: /* square root */
 				{
 					/* no negative numbers */
-					if (arg > 0.0f)
+					if (arg > 0.0f) {
 						fn= sqrt;
-					else
-						*cvalue= 0.0f; /* no vlaue possible here */
+					}
+					else {
+						if ((data->flag & FCM_GENERATOR_ADDITIVE) == 0)
+							*cvalue = 0.0f; /* no value possible here */
+					}
 				}
 					break;
 					
@@ -1353,8 +1369,14 @@ static void fcm_generator_evaluate (FCurve *fcu, FModifier *fcm, float *cvalue,
 			}
 			
 			/* execute function callback to set value if appropriate */
-			if (fn)
-				*cvalue= data->coefficients[0]*fn(arg) + data->coefficients[3];
+			if (fn) {
+				float value= data->coefficients[0]*fn(arg) + data->coefficients[3];
+				
+				if (data->flag & FCM_GENERATOR_ADDITIVE)
+					*cvalue += value;
+				else
+					*cvalue= value;
+			}
 		}
 			break;
 
@@ -1446,6 +1468,7 @@ static void fcm_envelope_evaluate (FCurve *fcu, FModifier *fcm, float *cvalue, f
 	}
 	else {
 		/* evaltime occurs somewhere between segments */
+		// TODO: implement binary search for this to make it faster?
 		for (a=0; prevfed && fed && (a < env->totvert-1); a++, prevfed=fed, fed++) {  
 			/* evaltime occurs within the interval defined by these two envelope points */
 			if ((prevfed->time <= evaltime) && (fed->time >= evaltime)) {