1 files changed, 87 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/analysis/interpolation/InterpolatingMicrosphere2D.java b/src/main/java/org/apache/commons/math3/analysis/interpolation/InterpolatingMicrosphere2D.java
new file mode 100644
index 0000000..fdc01b2
--- /dev/null
+++ b/src/main/java/org/apache/commons/math3/analysis/interpolation/InterpolatingMicrosphere2D.java
@@ -0,0 +1,87 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.math3.analysis.interpolation;
+
+import org.apache.commons.math3.util.FastMath;
+import org.apache.commons.math3.util.MathUtils;
+
+/**
+ * Utility class for the {@link MicrosphereProjectionInterpolator} algorithm.
+ * For 2D interpolation, this class constructs the microsphere as a series of
+ * evenly spaced facets (rather than generating random normals as in the
+ * base implementation).
+ *
+ * @since 3.6
+ */
+public class InterpolatingMicrosphere2D extends InterpolatingMicrosphere {
+    /** Space dimension. */
+    private static final int DIMENSION = 2;
+
+    /**
+     * Create a sphere from vectors regularly sampled around a circle.
+     *
+     * @param size Number of surface elements of the sphere.
+     * @param maxDarkFraction Maximum fraction of the facets that can be dark.
+     * If the fraction of "non-illuminated" facets is larger, no estimation
+     * of the value will be performed, and the {@code background} value will
+     * be returned instead.
+     * @param darkThreshold Value of the illumination below which a facet is
+     * considered dark.
+     * @param background Value returned when the {@code maxDarkFraction}
+     * threshold is exceeded.
+     * @throws org.apache.commons.math3.exception.NotStrictlyPositiveException
+     * if {@code size <= 0}.
+     * @throws org.apache.commons.math3.exception.NotPositiveException if
+     * {@code darkThreshold < 0}.
+     * @throws org.apache.commons.math3.exception.OutOfRangeException if
+     * {@code maxDarkFraction} does not belong to the interval {@code [0, 1]}.
+     */
+    public InterpolatingMicrosphere2D(int size,
+                                      double maxDarkFraction,
+                                      double darkThreshold,
+                                      double background) {
+        super(DIMENSION, size, maxDarkFraction, darkThreshold, background);
+
+        // Generate the microsphere normals.
+        for (int i = 0; i < size; i++) {
+            final double angle = i * MathUtils.TWO_PI / size;
+
+            add(new double[] { FastMath.cos(angle),
+                               FastMath.sin(angle) },
+                false);
+        }
+    }
+
+    /**
+     * Copy constructor.
+     *
+     * @param other Instance to copy.
+     */
+    protected InterpolatingMicrosphere2D(InterpolatingMicrosphere2D other) {
+        super(other);
+    }
+
+    /**
+     * Perform a copy.
+     *
+     * @return a copy of this instance.
+     */
+    @Override
+    public InterpolatingMicrosphere2D copy() {
+        return new InterpolatingMicrosphere2D(this);
+    }
+}