Rename extlibs to thirdparty

thirdparty/include/chipmunk/cpMarch.h

@@ -0,0 +1,28 @@
+// Copyright 2013 Howling Moon Software. All rights reserved.
+// See http://chipmunk2d.net/legal.php for more information.
+
+/// Function type used as a callback from the marching squares algorithm to sample an image function.
+/// It passes you the point to sample and your context pointer, and you return the density.
+typedef cpFloat (*cpMarchSampleFunc)(cpVect point, void *data);
+
+/// Function type used as a callback from the marching squares algorithm to output a line segment.
+/// It passes you the two endpoints and your context pointer.
+typedef void (*cpMarchSegmentFunc)(cpVect v0, cpVect v1, void *data);
+
+/// Trace an anti-aliased contour of an image along a particular threshold.
+/// The given number of samples will be taken and spread across the bounding box area using the sampling function and context.
+/// The segment function will be called for each segment detected that lies along the density contour for @c threshold.
+CP_EXPORT void cpMarchSoft(
+  cpBB bb, unsigned long x_samples, unsigned long y_samples, cpFloat threshold,
+  cpMarchSegmentFunc segment, void *segment_data,
+  cpMarchSampleFunc sample, void *sample_data
+);
+
+/// Trace an aliased curve of an image along a particular threshold.
+/// The given number of samples will be taken and spread across the bounding box area using the sampling function and context.
+/// The segment function will be called for each segment detected that lies along the density contour for @c threshold.
+CP_EXPORT void cpMarchHard(
+  cpBB bb, unsigned long x_samples, unsigned long y_samples, cpFloat threshold,
+  cpMarchSegmentFunc segment, void *segment_data,
+  cpMarchSampleFunc sample, void *sample_data
+);