Added support for back easing functions. Easier than anticipated. Nee…

…ds optimization, but that's what contributors are for
warrenm · Jun 3, 2011 · a651ada · a651ada
1 parent ebebd2d
commit a651ada
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Showing 4 changed files with 27 additions and 8 deletions.
diff --git a/AHEasing/PlaygroundViewController.m b/AHEasing/PlaygroundViewController.m
@@ -122,6 +122,8 @@ - (void)configureEasingFunction
 		case CurveTypeElastic:
 			currentFunction = (currentEasing == EaseIn) ? ElasticEaseIn : (currentEasing == EaseOut) ? ElasticEaseOut : ElasticEaseInOut;
 			break;
+		case CurveTypeBack:
+			currentFunction = (currentEasing == EaseIn) ? BackEaseIn : (currentEasing == EaseOut) ? BackEaseOut : BackEaseInOut;
 	}
 
 	[graphView setEasingFunction:currentFunction];

diff --git a/AHEasing/easing.c b/AHEasing/easing.c
@@ -234,19 +234,31 @@ AHFloat ElasticEaseInOut(AHFloat p)
 	}
 }
 
+// Modeled after the overshooting cubic y = x^3 - x*sin(x*pi)
 AHFloat BackEaseIn(AHFloat p)
 {
-	return p;
+	return p * p * p - p * sin(p * M_PI);
 }
 
+// Modeled after overshooting cubic y = 1 - ((1-x)^3 - (1-x)*sin((1-x)*pi))
 AHFloat BackEaseOut(AHFloat p)
 {
-	return p;
+	AHFloat f = (1 - p);
+	return 1 - (f * f * f - f * sin(f * M_PI));
 }
 
 AHFloat BackEaseInOut(AHFloat p)
 {
-	return p;
+	if(p < 0.5)
+	{
+		AHFloat f = 2 * p;
+		return 0.5 * (f * f * f - f * sin(f * M_PI));
+	}
+	else
+	{
+		AHFloat f = (1 - (2 * p - 1));
+		return 0.5 * (1 - (f * f * f - f * sin(f * M_PI))) + 0.5;
+	}
 }
 
 AHFloat BounceEaseIn(AHFloat p)

diff --git a/AHEasing/easing.h b/AHEasing/easing.h
@@ -64,10 +64,10 @@ AHFloat ElasticEaseIn(AHFloat p);
 AHFloat ElasticEaseOut(AHFloat p);
 AHFloat ElasticEaseInOut(AHFloat p);
 
-// Overshooting cubic easing
-//AHFloat BackEaseIn(AHFloat p);
-//AHFloat BackEaseOut(AHFloat p);
-//AHFloat BackEaseInOut(AHFloat p);
+// Overshooting cubic easing; 
+AHFloat BackEaseIn(AHFloat p);
+AHFloat BackEaseOut(AHFloat p);
+AHFloat BackEaseInOut(AHFloat p);
 
 // Exponentially-decaying bounce easing
 //AHFloat BounceEaseIn(AHFloat p);

diff --git a/AHEasing/en.lproj/PlaygroundView.xib b/AHEasing/en.lproj/PlaygroundView.xib
@@ -88,7 +88,7 @@
 						<bool key="IBUIOpaque">NO</bool>
 						<string key="targetRuntimeIdentifier">IBCocoaTouchFramework</string>
 						<int key="IBSegmentControlStyle">2</int>
-						<int key="IBNumberOfSegments">9</int>
+						<int key="IBNumberOfSegments">10</int>
 						<int key="IBSelectedSegmentIndex">0</int>
 						<object class="NSArray" key="IBSegmentTitles">
 							<bool key="EncodedWithXMLCoder">YES</bool>
@@ -101,6 +101,7 @@
 							<string>Circ</string>
 							<string>Exp</string>
 							<string>Elastic</string>
+							<string>Back</string>
 						</object>
 						<object class="NSMutableArray" key="IBSegmentWidths">
 							<bool key="EncodedWithXMLCoder">YES</bool>
@@ -113,6 +114,7 @@
 							<real value="0.0"/>
 							<real value="0.0"/>
 							<real value="0.0"/>
+							<real value="0.0"/>
 						</object>
 						<object class="NSMutableArray" key="IBSegmentEnabledStates">
 							<bool key="EncodedWithXMLCoder">YES</bool>
@@ -125,6 +127,7 @@
 							<boolean value="YES"/>
 							<boolean value="YES"/>
 							<boolean value="YES"/>
+							<boolean value="YES"/>
 						</object>
 						<object class="NSMutableArray" key="IBSegmentContentOffsets">
 							<bool key="EncodedWithXMLCoder">YES</bool>
@@ -137,6 +140,7 @@
 							<string>{0, 0}</string>
 							<string>{0, 0}</string>
 							<string>{0, 0}</string>
+							<string>{0, 0}</string>
 						</object>
 						<object class="NSMutableArray" key="IBSegmentImages">
 							<bool key="EncodedWithXMLCoder">YES</bool>
@@ -149,6 +153,7 @@
 							<reference ref="4"/>
 							<reference ref="4"/>
 							<reference ref="4"/>
+							<reference ref="4"/>
 						</object>
 					</object>
 					<object class="IBUISegmentedControl" id="942628741">