Preparation to add signed distance field collision detection.

btMiniSDF is based on https://github.com/InteractiveComputerGraphics/Discregrid

src/BulletCollision/CollisionShapes/btMiniSDF.h

@@ -0,0 +1,134 @@
+#ifndef MINISDF_H
+#define MINISDF_H
+
+#include "LinearMath/btVector3.h"
+#include "LinearMath/btAabbUtil2.h"
+#include "Linearmath/btAlignedObjectArray.h"
+
+
+struct btMultiIndex
+{
+	unsigned int ijk[3];
+};
+
+struct btAlignedBox3d
+{
+	btVector3 m_min;
+	btVector3 m_max;
+
+	const btVector3& min() const
+	{
+		return m_min;
+	}
+
+	const btVector3& max() const
+	{
+		return m_max;
+	}
+	
+
+	bool contains(const btVector3& x) const
+	{
+		return TestPointAgainstAabb2(m_min, m_max, x);
+	}
+
+	btAlignedBox3d(const btVector3& mn, const btVector3& mx)
+		:m_min(mn),
+		m_max(mx)
+	{
+	}
+
+	btAlignedBox3d()
+	{
+	}
+};
+
+struct btShapeMatrix
+{
+	double m_vec[32];
+
+	inline double&       operator[](int i)
+	{
+		return m_vec[i];
+	}
+
+	inline const double&       operator[](int i) const
+	{
+		return m_vec[i];
+	}
+
+};
+
+struct btShapeGradients
+{
+	btVector3	m_vec[32];
+
+	void topRowsDivide(int row, double denom)
+	{
+		for (int i=0;i<row;i++)
+		{
+			m_vec[i] /= denom;
+		}
+	}
+	
+	void bottomRowsMul(int row, double val)
+	{
+		for (int i=32-row;i<32;i++)
+		{
+			m_vec[i] *= val;
+		}
+	}
+	
+	inline double&       operator()(int i, int j)
+	{
+		return m_vec[i][j];
+	}
+};
+
+struct btCell32
+{
+	unsigned int m_cells[32];
+};
+
+struct btMiniSDF
+{
+
+	btAlignedBox3d m_domain;
+	unsigned int m_resolution[3];
+	btVector3 m_cell_size;
+	btVector3 m_inv_cell_size;
+	std::size_t m_n_cells;
+	std::size_t m_n_fields;
+	bool m_isValid;
+
+
+	btAlignedObjectArray<btAlignedObjectArray<double> > m_nodes;
+	btAlignedObjectArray<btAlignedObjectArray<btCell32 > > m_cells;
+	btAlignedObjectArray<btAlignedObjectArray<unsigned int> > m_cell_map;
+
+	btMiniSDF()
+	:m_isValid(false)
+	{
+	}
+	bool load(const char* data, int size);
+	bool isValid() const
+	{
+		return m_isValid;
+	}
+	unsigned int multiToSingleIndex(btMultiIndex const & ijk) const;
+	
+	btAlignedBox3d subdomain(btMultiIndex const& ijk) const;
+
+	btMultiIndex singleToMultiIndex(unsigned int l) const;
+
+	btAlignedBox3d subdomain(unsigned int l) const;
+
+
+	btShapeMatrix
+	shape_function_(btVector3 const& xi, btShapeGradients* gradient = 0) const;
+
+	bool interpolate(unsigned int field_id, double& dist, btVector3 const& x, btVector3* gradient) const;
+};
+
+
+#endif //MINISDF_H