First Commit

src/main/java/eu/crushedpixel/replaymod/interpolation/BasicSpline.java

@@ -0,0 +1,71 @@
+package eu.crushedpixel.replaymod.interpolation;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Collection;
+import java.util.List;
+
+public abstract class BasicSpline {
+	public void calcNaturalCubic(List valueCollection, Field val, Collection<Cubic> cubicCollection) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
+		int num = valueCollection.size()-1;
+
+		double[] gamma = new double[num+1];
+		double[] delta = new double[num+1];
+		double[] D = new double[num+1];
+
+		int i;
+		/*
+	           We solve the equation
+	          [2 1       ] [D[0]]   [3(x[1] - x[0])  ]
+	          |1 4 1     | |D[1]|   |3(x[2] - x[0])  |
+	          |  1 4 1   | | .  | = |      .         |
+	          |    ..... | | .  |   |      .         |
+	          |     1 4 1| | .  |   |3(x[n] - x[n-2])|
+	          [       1 2] [D[n]]   [3(x[n] - x[n-1])]
+
+	          by using row operations to convert the matrix to upper triangular
+	          and then back sustitution.  The D[i] are the derivatives at the knots.
+		 */
+		gamma[0] = 1.0f / 2.0f;
+		for(i=1; i< num; i++) {
+			gamma[i] = 1.0f/(4.0f - gamma[i-1]);
+		}
+		gamma[num] = 1.0f/(2.0f - gamma[num-1]);
+
+		Double p0 = val.getDouble(valueCollection.get(0));
+		Double p1 = val.getDouble(valueCollection.get(1));
+
+		delta[0] = 3.0f * (p1 - p0) * gamma[0];
+		for(i=1; i< num; i++) {
+			p0 = val.getDouble(valueCollection.get(i-1));
+			p1 = val.getDouble(valueCollection.get(i+1));
+			delta[i] = (3.0f * (p1 - p0) - delta[i - 1]) * gamma[i];
+		}
+		p0 = val.getDouble(valueCollection.get(num-1));
+		p1 = val.getDouble(valueCollection.get(num));
+
+		delta[num] = (3.0f * (p1 - p0) - delta[num - 1]) * gamma[num];
+
+		D[num] = delta[num];
+		for(i=num-1; i >= 0; i--) {
+			D[i] = delta[i] - gamma[i] * D[i+1];
+		}
+
+	    //now compute the coefficients of the cubics
+		cubicCollection.clear();
+
+		for(i=0; i<num; i++) {
+			p0 = val.getDouble(valueCollection.get(i));
+			p1 = val.getDouble(valueCollection.get(i+1));
+
+			cubicCollection.add(new Cubic(
+					p0, 
+					D[i], 
+					3*(p1 - p0) - 2*D[i] - D[i+1],
+					2*(p0 - p1) +   D[i] + D[i+1]
+					)
+					);
+		}
+	}
+}