CWE-ou-minkata/Sources/Plasma/CoreLib/hsFastMath.cpp

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#include "HeadSpin.h"
#pragma hdrstop

#include "hsGeometry3.h"
#include "hsFastMath.h"

const float hsFastMath::kSqrtTwo = sqrt(2.f);
const float hsFastMath::kInvSqrtTwo = hsInvert(hsFastMath::kSqrtTwo);
const float hsFastMath::kTwoPI = M_PI * 2.f;

hsPoint2 statCosSinTable[9] = // must match length in inline
{
    { 1.f, 0.f },
    { hsFastMath::kInvSqrtTwo, hsFastMath::kInvSqrtTwo },
    { 0.f, 1.f },
    { -hsFastMath::kInvSqrtTwo, hsFastMath::kInvSqrtTwo },
    { -1.f, 0.f },
    { -hsFastMath::kInvSqrtTwo, -hsFastMath::kInvSqrtTwo },
    { 0.f, -1.f },
    { hsFastMath::kInvSqrtTwo, -hsFastMath::kInvSqrtTwo },
    { 1.f, 0.f }
};

const hsPoint2* hsFastMath::fCosSinTable = statCosSinTable;

unsigned char statSeedTable[] = {
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};

float hsFastMath::IATan2OverTwoPi(float y, float x)
{
    const int tabSize = 16; // pad with one extra because hi can go hi
    const int tabMax = tabSize-1;
    static float tab[tabSize+1] = {
                    0.f,
                    0.0105947f,
                    0.0210962f,
                    0.0314165f,
                    0.0414762f,
                    0.0512082f,
                    0.0605595f,
                    0.0694914f,
                    0.0779791f,
                    0.0860104f,
                    0.0935835f,
                    0.100705f,
                    0.107388f,
                    0.113651f,
                    0.119514f,
                    0.125f,
                    0 };

    if( (x == 0)&&(y == 0) )
        return 0;

    int xNeg, yNeg;
    if((yNeg = (y < 0)))y = -y;
    if((xNeg = (x < 0)))x = -x;
    bool yBigger = y >= x;
    float div = yBigger ? x / y : y / x;

    float fInd = div * tabMax;
    int lo = int(fInd);
    int hi = lo+1;
    float frac = fInd - lo;

    float res = tab[lo];
    res += frac * (tab[hi] - res);

    // now move to proper half quadrant
    hsAssert((res >= 0)&&(res <= 0.25f), "Lookup atan2 out of bounds");
    if( yBigger )
        res = 0.25f - res;
    switch( (yNeg << 1)|xNeg )
    {
    case 0:
        break;
    case 1:
        res = 0.5f - res;
        break;
    case 3:
        res += 0.5f;
        break;
    case 2:
        res = 1.f - res;
        break;
    }
    return res;
}