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-rw-r--r--libdimension/checker.c58
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diff --git a/libdimension/checker.c b/libdimension/checker.c
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+/*************************************************************************
+ * Copyright (C) 2010 Tavian Barnes <tavianator@gmail.com> *
+ * *
+ * This file is part of The Dimension Library. *
+ * *
+ * The Dimension Library is free software; you can redistribute it and/ *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version. *
+ * *
+ * The Dimension Library is distributed in the hope that it will be *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
+ * Lesser General Public License for more details. *
+ * *
+ * You should have received a copy of the GNU Lesser General Public *
+ * License along with this program. If not, see *
+ * <http://www.gnu.org/licenses/>. *
+ *************************************************************************/
+
+#include "dimension.h"
+
+/*
+ * Checker pattern
+ */
+
+static double
+dmnsn_checker_pattern_fn(const dmnsn_pattern *checker, dmnsn_vector v)
+{
+ double xmod = fmod(v.x, 2.0);
+ double ymod = fmod(v.y, 2.0);
+ double zmod = fmod(v.z, 2.0);
+
+ if (xmod < -dmnsn_epsilon)
+ xmod += 2.0;
+ if (ymod < -dmnsn_epsilon)
+ ymod += 2.0;
+ if (zmod < -dmnsn_epsilon)
+ zmod += 2.0;
+
+ /* Return 0 when an even number of coordinates are in [0, 1), 1 otherwise */
+ unsigned int n = 0;
+ if (xmod >= 1.0)
+ ++n;
+ if (ymod >= 1.0)
+ ++n;
+ if (zmod >= 1.0)
+ ++n;
+ return (n%2 == 0) ? 0.0 : 1.0;
+}
+
+dmnsn_pattern *
+dmnsn_new_checker_pattern()
+{
+ dmnsn_pattern *checker = dmnsn_new_pattern();
+ checker->pattern_fn = &dmnsn_checker_pattern_fn;
+ return checker;
+}