added missing xml docs

com.unity.perception/Runtime/Randomization/Samplers/SamplerUtility.cs

         /// <param name="interval">The interval at which the original AnimationCurve was sampled in order to produce integratedCurve</param>
         /// <param name="startTime">The time attribute of the first key of the original AnimationCurve</param>
         /// <param name="endTime">The time attribute of the last key of the original AnimationCurve</param>
-        /// <returns></returns>
+        /// <returns>The generated sample</returns>
-            for (int i = 0; i < integratedCurve.Length - 1; i++)
+            for (var i = 0; i < integratedCurve.Length - 1; i++)
             {
                 if (scaledSample > integratedCurve[i] && scaledSample < integratedCurve[i + 1])
                 {
                     return matchingTimeStamp;
                 }
             }
-            Debug.LogError("Could not find matching timestamp.");
-            return -1;
+            throw new ArithmeticException("Could not find matching timestamp.");
         }
 
         /// <summary>
         /// </summary>
+        /// <param name="array">The array to fill with integrated values</param>
+        /// <param name="curve">The animation curve to sample integrate</param>
+        /// <exception cref="ArgumentException"></exception>
         public static void IntegrateCurve(float[] array, AnimationCurve curve)
         {
             if (curve.length == 0)
             array[0] = 0;
             var previousValue = curve.Evaluate(startTime);
 
-            for (int i = 1; i < array.Length; i++)
+            for (var i = 1; i < array.Length; i++)
             {
                 if (curve.length == 1)
                 {

com.unity.perception/Runtime/Randomization/Samplers/SamplerValidationException.cs

 
 namespace UnityEngine.Experimental.Perception.Randomization.Samplers
 {
-    public class SamplerValidationException : Exception
+    class SamplerValidationException : Exception
     {
         public SamplerValidationException(string msg) : base(msg) {}
         public SamplerValidationException(string msg, Exception innerException) : base(msg, innerException) {}