1 files changed, 251 insertions, 0 deletions
diff --git a/src/LinearInterpolation.cpp b/src/LinearInterpolation.cpp
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+++ b/src/LinearInterpolation.cpp
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+
+// LinearInterpolation.cpp
+
+// Implements methods for linear interpolation over 1D, 2D and 3D arrays
+
+#include "Globals.h"
+#include "LinearInterpolation.h"
+
+
+
+
+
+/*
+// Perform an automatic test upon program start (use breakpoints to debug):
+
+extern void Debug3DNoise(float * a_Noise, int a_SizeX, int a_SizeY, int a_SizeZ, const AString & a_FileNameBase);
+
+class Test
+{
+public:
+	Test(void)
+	{
+		// DoTest1();
+		DoTest2();
+	}
+	
+	
+	void DoTest1(void)
+	{
+		float In[8] = {0, 1, 2, 3, 1, 2, 2, 2};
+		float Out[3 * 3 * 3];
+		LinearInterpolate1DArray(In, 4, Out, 9);
+		LinearInterpolate2DArray(In, 2, 2, Out, 3, 3);
+		LinearInterpolate3DArray(In, 2, 2, 2, Out, 3, 3, 3);
+		LOGD("Out[0]: %f", Out[0]);
+	}
+	
+	
+	void DoTest2(void)
+	{
+		float In[3 * 3 * 3];
+		for (int i = 0; i < ARRAYCOUNT(In); i++)
+		{
+			In[i] = (float)(i % 5);
+		}
+		float Out[15 * 16 * 17];
+		LinearInterpolate3DArray(In, 3, 3, 3, Out, 15, 16, 17);
+		Debug3DNoise(Out, 15, 16, 17, "LERP test");
+	}
+} gTest;
+//*/
+
+
+
+
+
+// Puts linearly interpolated values from one array into another array. 1D version
+void LinearInterpolate1DArray(
+	float * a_Src,
+	int a_SrcSizeX,
+	float * a_Dst,
+	int a_DstSizeX
+)
+{
+	a_Dst[0] = a_Src[0];
+	int DstSizeXm1 = a_DstSizeX - 1;
+	int SrcSizeXm1 = a_SrcSizeX - 1;
+	float fDstSizeXm1 = (float)DstSizeXm1;
+	float fSrcSizeXm1 = (float)SrcSizeXm1;
+	for (int x = 1; x < DstSizeXm1; x++)
+	{
+		int SrcIdx = x * SrcSizeXm1 / DstSizeXm1;
+		float ValLo = a_Src[SrcIdx];
+		float ValHi = a_Src[SrcIdx + 1];
+		float Ratio = (float)x * fSrcSizeXm1 / fDstSizeXm1 - SrcIdx;
+		a_Dst[x] = ValLo + (ValHi - ValLo) * Ratio;
+	}
+	a_Dst[a_DstSizeX - 1] = a_Src[a_SrcSizeX - 1];
+}
+
+
+
+
+
+// Puts linearly interpolated values from one array into another array. 2D version
+void LinearInterpolate2DArray(
+	float * a_Src,
+	int a_SrcSizeX, int a_SrcSizeY,
+	float * a_Dst,
+	int a_DstSizeX, int a_DstSizeY
+)
+{
+	ASSERT(a_DstSizeX > 0);
+	ASSERT(a_DstSizeX < MAX_INTERPOL_SIZEX);
+	ASSERT(a_DstSizeY > 0);
+	ASSERT(a_DstSizeY < MAX_INTERPOL_SIZEY);
+	
+	// Calculate interpolation ratios and src indices along each axis:
+	float RatioX[MAX_INTERPOL_SIZEX];
+	float RatioY[MAX_INTERPOL_SIZEY];
+	int   SrcIdxX[MAX_INTERPOL_SIZEX];
+	int   SrcIdxY[MAX_INTERPOL_SIZEY];
+	for (int x = 1; x < a_DstSizeX; x++)
+	{
+		SrcIdxX[x] = x * (a_SrcSizeX - 1) / (a_DstSizeX - 1);
+		RatioX[x] = ((float)(x * (a_SrcSizeX - 1)) / (a_DstSizeX - 1)) - SrcIdxX[x];
+	}
+	for (int y = 1; y < a_DstSizeY; y++)
+	{
+		SrcIdxY[y] = y * (a_SrcSizeY - 1) / (a_DstSizeY - 1);
+		RatioY[y] = ((float)(y * (a_SrcSizeY - 1)) / (a_DstSizeY - 1)) - SrcIdxY[y];
+	}
+	
+	// Special values at the ends. Notice especially the last indices being (size - 2) with ratio set to 1, to avoid index overflow:
+	SrcIdxX[0] = 0;
+	RatioX[0] = 0;
+	SrcIdxY[0] = 0;
+	RatioY[0] = 0;
+	SrcIdxX[a_DstSizeX - 1] = a_SrcSizeX - 2;
+	RatioX[a_DstSizeX - 1] = 1;
+	SrcIdxY[a_DstSizeY - 1] = a_SrcSizeY - 2;
+	RatioY[a_DstSizeY - 1] = 1;
+	
+	// Output all the dst array values using the indices and ratios:
+	int idx = 0;
+	for (int y = 0; y < a_DstSizeY; y++)
+	{
+		int idxLoY = a_SrcSizeX * SrcIdxY[y];
+		int idxHiY = a_SrcSizeX * (SrcIdxY[y] + 1);
+		float ry = RatioY[y];
+		for (int x = 0; x < a_DstSizeX; x++)
+		{
+			// The four src corners of the current "cell":
+			float LoXLoY = a_Src[SrcIdxX[x] +     idxLoY];
+			float HiXLoY = a_Src[SrcIdxX[x] + 1 + idxLoY];
+			float LoXHiY = a_Src[SrcIdxX[x] +     idxHiY];
+			float HiXHiY = a_Src[SrcIdxX[x] + 1 + idxHiY];
+			
+			// Linear interpolation along the X axis:
+			float InterpXLoY = LoXLoY + (HiXLoY - LoXLoY) * RatioX[x];
+			float InterpXHiY = LoXHiY + (HiXHiY - LoXHiY) * RatioX[x];
+			
+			// Linear interpolation along the Y axis:
+			a_Dst[idx] = InterpXLoY + (InterpXHiY - InterpXLoY) * ry;
+			idx += 1;
+		}
+	}
+}
+
+
+
+
+
+/// Puts linearly interpolated values from one array into another array. 3D version
+void LinearInterpolate3DArray(
+	float * a_Src,
+	int a_SrcSizeX, int a_SrcSizeY, int a_SrcSizeZ,
+	float * a_Dst,
+	int a_DstSizeX, int a_DstSizeY, int a_DstSizeZ
+)
+{
+	ASSERT(a_DstSizeX > 0);
+	ASSERT(a_DstSizeX < MAX_INTERPOL_SIZEX);
+	ASSERT(a_DstSizeY > 0);
+	ASSERT(a_DstSizeY < MAX_INTERPOL_SIZEY);
+	ASSERT(a_DstSizeZ > 0);
+	ASSERT(a_DstSizeZ < MAX_INTERPOL_SIZEZ);
+
+	// Calculate interpolation ratios and src indices along each axis:
+	float RatioX[MAX_INTERPOL_SIZEX];
+	float RatioY[MAX_INTERPOL_SIZEY];
+	float RatioZ[MAX_INTERPOL_SIZEZ];
+	int   SrcIdxX[MAX_INTERPOL_SIZEX];
+	int   SrcIdxY[MAX_INTERPOL_SIZEY];
+	int   SrcIdxZ[MAX_INTERPOL_SIZEZ];
+	for (int x = 1; x < a_DstSizeX; x++)
+	{
+		SrcIdxX[x] = x * (a_SrcSizeX - 1) / (a_DstSizeX - 1);
+		RatioX[x] = ((float)(x * (a_SrcSizeX - 1)) / (a_DstSizeX - 1)) - SrcIdxX[x];
+	}
+	for (int y = 1; y < a_DstSizeY; y++)
+	{
+		SrcIdxY[y] = y * (a_SrcSizeY - 1) / (a_DstSizeY - 1);
+		RatioY[y] = ((float)(y * (a_SrcSizeY - 1)) / (a_DstSizeY - 1)) - SrcIdxY[y];
+	}
+	for (int z = 1; z < a_DstSizeZ; z++)
+	{
+		SrcIdxZ[z] = z * (a_SrcSizeZ - 1) / (a_DstSizeZ - 1);
+		RatioZ[z] = ((float)(z * (a_SrcSizeZ - 1)) / (a_DstSizeZ - 1)) - SrcIdxZ[z];
+	}
+
+	// Special values at the ends. Notice especially the last indices being (size - 2) with ratio set to 1, to avoid index overflow:
+	SrcIdxX[0] = 0;
+	RatioX[0]  = 0;
+	SrcIdxY[0] = 0;
+	RatioY[0]  = 0;
+	SrcIdxZ[0] = 0;
+	RatioZ[0]  = 0;
+	SrcIdxX[a_DstSizeX - 1] = a_SrcSizeX - 2;
+	RatioX[a_DstSizeX - 1]  = 1;
+	SrcIdxY[a_DstSizeY - 1] = a_SrcSizeY - 2;
+	RatioY[a_DstSizeY - 1]  = 1;
+	SrcIdxZ[a_DstSizeZ - 1] = a_SrcSizeZ - 2;
+	RatioZ[a_DstSizeZ - 1]  = 1;
+
+	// Output all the dst array values using the indices and ratios:
+	int idx = 0;
+	for (int z = 0; z < a_DstSizeZ; z++)
+	{
+		int idxLoZ = a_SrcSizeX * a_SrcSizeY * SrcIdxZ[z];
+		int idxHiZ = a_SrcSizeX * a_SrcSizeY * (SrcIdxZ[z] + 1);
+		float rz = RatioZ[z];
+		for (int y = 0; y < a_DstSizeY; y++)
+		{
+			int idxLoY = a_SrcSizeX * SrcIdxY[y];
+			int idxHiY = a_SrcSizeX * (SrcIdxY[y] + 1);
+			float ry = RatioY[y];
+			for (int x = 0; x < a_DstSizeX; x++)
+			{
+				// The eight src corners of the current "cell":
+				float LoXLoYLoZ = a_Src[SrcIdxX[x] +     idxLoY + idxLoZ];
+				float HiXLoYLoZ = a_Src[SrcIdxX[x] + 1 + idxLoY + idxLoZ];
+				float LoXHiYLoZ = a_Src[SrcIdxX[x] +     idxHiY + idxLoZ];
+				float HiXHiYLoZ = a_Src[SrcIdxX[x] + 1 + idxHiY + idxLoZ];
+				float LoXLoYHiZ = a_Src[SrcIdxX[x] +     idxLoY + idxHiZ];
+				float HiXLoYHiZ = a_Src[SrcIdxX[x] + 1 + idxLoY + idxHiZ];
+				float LoXHiYHiZ = a_Src[SrcIdxX[x] +     idxHiY + idxHiZ];
+				float HiXHiYHiZ = a_Src[SrcIdxX[x] + 1 + idxHiY + idxHiZ];
+
+				// Linear interpolation along the Z axis:
+				float LoXLoYInZ = LoXLoYLoZ + (LoXLoYHiZ - LoXLoYLoZ) * rz;
+				float HiXLoYInZ = HiXLoYLoZ + (HiXLoYHiZ - HiXLoYLoZ) * rz;
+				float LoXHiYInZ = LoXHiYLoZ + (LoXHiYHiZ - LoXHiYLoZ) * rz;
+				float HiXHiYInZ = HiXHiYLoZ + (HiXHiYHiZ - HiXHiYLoZ) * rz;
+
+				// Linear interpolation along the Y axis:
+				float LoXInYInZ = LoXLoYInZ + (LoXHiYInZ - LoXLoYInZ) * ry;
+				float HiXInYInZ = HiXLoYInZ + (HiXHiYInZ - HiXLoYInZ) * ry;
+				
+				// Linear interpolation along the X axis:
+				a_Dst[idx] = LoXInYInZ + (HiXInYInZ - LoXInYInZ) * RatioX[x];
+				idx += 1;
+			}  // for x
+		}  // for y
+	}  // for z
+}
+
+
+
+
+