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Diffstat (limited to '')
| -rw-r--r-- | source/LinearInterpolation.cpp | 251 |
1 files changed, 251 insertions, 0 deletions
diff --git a/source/LinearInterpolation.cpp b/source/LinearInterpolation.cpp new file mode 100644 index 000000000..d4536662e --- /dev/null +++ b/source/LinearInterpolation.cpp @@ -0,0 +1,251 @@ +
+// 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
+}
+
+
+
+
+
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