FModifier Influence/BlendIn-Out

Following on from my commit to introduce frame ranges for FModifiers,
those frame ranges can now have blend in/out values. By setting a
blendin or blendout value, you're specifying the number of frames for
the modifier's "full influence" to take effect or fade out relative to
the start/end frames.

The "full influence" above needs a little clarification.

When the "use influence" setting is enabled, "full influence" is taken
from the "influence" slider (a new setting). Otherwise, it uses 1.0
(i.e. unmodified influence, same as old behaviour before the
introduction of influence controls). The influence slider basically
says how much the modifier's effects are allowed to contribute to the
final result.

---

Notes:
- This opt-in "Use Influence" approach is really forced upon us
because there are heaps of old files for which we cannot easily
version patch without spending some effort going through all the data
in the file, hunting out the F-Modifiers.
- interpf() seems to use a backwards order compared to everything else

1 files changed, 55 insertions, 6 deletions

diff --git a/source/blender/blenkernel/intern/fmodifier.c b/source/blender/blenkernel/intern/fmodifier.c
index 4a1a0f9ac6b..dcf81c19479 100644
--- a/source/blender/blenkernel/intern/fmodifier.c
+++ b/source/blender/blenkernel/intern/fmodifier.c
@@ -1013,6 +1013,7 @@ FModifier *add_fmodifier (ListBase *modifiers, int type)
 	fcm= MEM_callocN(sizeof(FModifier), "F-Curve Modifier");
 	fcm->type = type;
 	fcm->flag = FMODIFIER_FLAG_EXPANDED;
+	fcm->influence = 1.0f;
 	BLI_addtail(modifiers, fcm);
 	
 	/* tag modifier as "active" if no other modifiers exist in the stack yet */
@@ -1200,6 +1201,47 @@ short list_has_suitable_fmodifier (ListBase *modifiers, int mtype, short acttype
 
 /* Evaluation API --------------------------- */
 
+/* helper function - calculate influence of FModifier */
+static float eval_fmodifier_influence (FModifier *fcm, float evaltime)
+{
+	float influence;
+	
+	/* sanity check */
+	if (fcm == NULL) 
+		return 0.0f;
+	
+	/* should we use influence stored in modifier or not 
+	 * NOTE: this is really just a hack so that we don't need to version patch old files ;)
+	 */
+	if (fcm->flag & FMODIFIER_FLAG_USEINFLUENCE)
+		influence = fcm->influence;
+	else
+		influence = 1.0f;
+		
+	/* restricted range or full range? */
+	if (fcm->flag & FMODIFIER_FLAG_RANGERESTRICT) {
+		if ((evaltime <= fcm->sfra) || (evaltime >= fcm->efra)) {
+			/* out of range */
+			return 0.0f;
+		}
+		else if ((evaltime > fcm->sfra) && (evaltime < fcm->sfra + fcm->blendin)) {
+			/* blend in range */
+			float a = fcm->sfra;
+			float b = fcm->sfra + fcm->blendin;
+			return influence * (evaltime - a) / (b - a);
+		}
+		else if ((evaltime < fcm->efra) && (evaltime > fcm->efra - fcm->blendout)) {
+			/* blend out range */
+			float a = fcm->efra;
+			float b = fcm->efra - fcm->blendout;
+			return influence * (evaltime - a) / (b - a);
+		}
+	}
+	
+	/* just return the influence of the modifier */
+	return influence;
+}
+
 /* evaluate time modifications imposed by some F-Curve Modifiers
  *	- this step acts as an optimisation to prevent the F-Curve stack being evaluated 
  *	  several times by modifiers requesting the time be modified, as the final result
@@ -1240,10 +1282,13 @@ float evaluate_time_fmodifiers (ListBase *modifiers, FCurve *fcu, float cvalue,
 			((fcm->sfra <= evaltime) && (fcm->efra >= evaltime)) )
 		{
 			/* only evaluate if there's a callback for this */
-			// TODO: implement the 'influence' control feature...
 			if (fmi->evaluate_modifier_time) {
-				if ((fcm->flag & (FMODIFIER_FLAG_DISABLED|FMODIFIER_FLAG_MUTED)) == 0)
-					evaltime= fmi->evaluate_modifier_time(fcu, fcm, cvalue, evaltime);
+				if ((fcm->flag & (FMODIFIER_FLAG_DISABLED|FMODIFIER_FLAG_MUTED)) == 0) {
+					float influence = eval_fmodifier_influence(fcm, evaltime);
+					float nval = fmi->evaluate_modifier_time(fcu, fcm, cvalue, evaltime);
+					
+					evaltime = interpf(nval, evaltime, influence);
+				}
 			}
 		}
 	}
@@ -1271,13 +1316,17 @@ void evaluate_value_fmodifiers (ListBase *modifiers, FCurve *fcu, float *cvalue,
 			continue;
 		
 		/* only evaluate if there's a callback for this, and if F-Modifier can be evaluated on this frame */
-		// TODO: implement the 'influence' control feature...
 		if ((fcm->flag & FMODIFIER_FLAG_RANGERESTRICT)==0 || 
 			((fcm->sfra <= evaltime) && (fcm->efra >= evaltime)) )
 		{
 			if (fmi->evaluate_modifier) {
-				if ((fcm->flag & (FMODIFIER_FLAG_DISABLED|FMODIFIER_FLAG_MUTED)) == 0)
-					fmi->evaluate_modifier(fcu, fcm, cvalue, evaltime);
+				if ((fcm->flag & (FMODIFIER_FLAG_DISABLED|FMODIFIER_FLAG_MUTED)) == 0) {
+					float influence = eval_fmodifier_influence(fcm, evaltime);
+					float nval = *cvalue;
+					
+					fmi->evaluate_modifier(fcu, fcm, &nval, evaltime);
+					*cvalue = interpf(nval, *cvalue, influence);
+				}
 			}
 		}
 	}