add vibration support + fix controller axes

src/Input/Gamepad.cs

@@ -1,4 +1,5 @@
 using System;
+using MoonWorks.Math;
 using SDL2;
 
 namespace MoonWorks.Input
@@ -35,6 +36,16 @@ namespace MoonWorks.Input
             Handle = handle;
         }
 
+        public bool SetVibration(float leftMotor, float rightMotor, uint durationInMilliseconds)
+        {
+            return SDL.SDL_GameControllerRumble(
+                Handle,
+                (ushort)(MathHelper.Clamp(leftMotor, 0f, 1f) * 0xFFFF),
+                (ushort)(MathHelper.Clamp(rightMotor, 0f, 1f) * 0xFFFF),
+                durationInMilliseconds
+            ) == 0;
+        }
+
         internal void Update()
         {
             A.Update(IsPressed(SDL.SDL_GameControllerButton.SDL_CONTROLLER_BUTTON_A));
@@ -69,19 +80,19 @@ namespace MoonWorks.Input
         private float UpdateAxis(SDL.SDL_GameControllerAxis axis)
         {
             var axisValue = SDL.SDL_GameControllerGetAxis(Handle, axis);
-            return Normalize(axisValue, short.MinValue, short.MaxValue);
+            return Normalize(axisValue, short.MinValue, short.MaxValue, -1, 1);
         }
 
         // Triggers only go from 0 to short.MaxValue
         private float UpdateTrigger(SDL.SDL_GameControllerAxis trigger)
         {
             var triggerValue = SDL.SDL_GameControllerGetAxis(Handle, trigger);
-            return Normalize(triggerValue, 0, short.MaxValue);
+            return Normalize(triggerValue, 0, short.MaxValue, 0, 1);
         }
 
-        private float Normalize(float value, short min, short max)
+        private float Normalize(float value, short min, short max, short newMin, short newMax)
         {
-            return (value - min) / (max - min);
+            return ((value - min) * (newMax - newMin)) / (max - min) + newMin;
         }
     }
 }

src/Input/Input.cs

@@ -36,6 +36,11 @@ namespace MoonWorks.Input
             }
         }
 
+        public bool GamepadExists(int slot)
+        {
+            return slot < gamepads.Count;
+        }
+
         public Gamepad GetGamepad(int slot)
         {
             return gamepads[slot];

src/Math/Vector3.cs

@@ -492,6 +492,19 @@ namespace MoonWorks.Math
 			result.Z = MathHelper.Clamp(value1.Z, min.Z, max.Z);
 		}
 
+		/// <summary>
+        /// Clamps the magnitude of the specified vector.
+        /// </summary>
+        /// <param name="value">The vector to clamp.</param>
+        /// <param name="maxLength">The maximum length of the vector.</param>
+        /// <returns></returns>
+		public static Vector3 ClampMagnitude(
+			Vector3 value,
+			float maxLength
+		) {
+            return (value.LengthSquared() > maxLength * maxLength) ? (Vector3.Normalize(value) * maxLength) : value;
+        }
+
 		/// <summary>
 		/// Computes the cross product of two vectors.
 		/// </summary>