ImfEnvmap.cpp

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2004, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
//
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///////////////////////////////////////////////////////////////////////////


//-----------------------------------------------------------------------------
//
//	Environment maps
//
//-----------------------------------------------------------------------------

#include <ImfEnvmap.h>
#include "ImathFun.h"
#include <algorithm>
#include <math.h>

using namespace std;
using namespace Imath;

namespace Imf {
namespace LatLongMap {

V2f
latLong (const V3f &dir)
{
    float r = sqrt (dir.z * dir.z + dir.x * dir.x);

    float latitude = (r < abs (dir.y))?
             acos (r / dir.length()) * sign (dir.y):
             asin (dir.y / dir.length());

    float longitude = (dir.z == 0 && dir.x == 0)? 0: atan2 (dir.x, dir.z);

    return V2f (latitude, longitude);
}


V2f
latLong (const Box2i &dataWindow, const V2f &pixelPosition)
{
    float latitude, longitude;

    if (dataWindow.max.y > dataWindow.min.y)
    {
    latitude = -M_PI *
          ((pixelPosition.y  - dataWindow.min.y) /
           (dataWindow.max.y - dataWindow.min.y) - 0.5f);
    }
    else
    {
    latitude = 0;
    }

    if (dataWindow.max.x > dataWindow.min.x)
    {
    longitude = -2 * M_PI *
           ((pixelPosition.x  - dataWindow.min.x) /
            (dataWindow.max.x - dataWindow.min.x) - 0.5f);
    }
    else
    {
    longitude = 0;
    }

    return V2f (latitude, longitude);
}


V2f
pixelPosition (const Box2i &dataWindow, const V2f &latLong)
{
    float x = latLong.y / (-2 * M_PI) + 0.5f;
    float y = latLong.x / -M_PI + 0.5f;

    return V2f (x * (dataWindow.max.x - dataWindow.min.x) + dataWindow.min.x,
        y * (dataWindow.max.y - dataWindow.min.y) + dataWindow.min.y);
}


V2f
pixelPosition (const Box2i &dataWindow, const V3f &direction)
{
    return pixelPosition (dataWindow, latLong (direction));
}


V3f
direction (const Box2i &dataWindow, const V2f &pixelPosition)
{
    V2f ll = latLong (dataWindow, pixelPosition);

    return V3f (sin (ll.y) * cos (ll.x),
        sin (ll.x),
        cos (ll.y) * cos (ll.x));
}

} // namespace LatLongMap


namespace CubeMap {

int
sizeOfFace (const Box2i &dataWindow)
{
    return min ((dataWindow.max.x - dataWindow.min.x + 1),
        (dataWindow.max.y - dataWindow.min.y + 1) / 6);
}


Box2i
dataWindowForFace (CubeMapFace face, const Box2i &dataWindow)
{
    int sof = sizeOfFace (dataWindow);
    Box2i dwf;

    dwf.min.x = 0;
    dwf.min.y = int (face) * sof;

    dwf.max.x = dwf.min.x + sof - 1;
    dwf.max.y = dwf.min.y + sof - 1;

    return dwf;
}


V2f
pixelPosition (CubeMapFace face, const Box2i &dataWindow, V2f positionInFace)
{
    Box2i dwf = dataWindowForFace (face, dataWindow);
    V2f pos (0, 0);

    switch (face)
    {
      case CUBEFACE_POS_X:

    pos.x = dwf.min.x + positionInFace.y;
    pos.y = dwf.max.y - positionInFace.x;
    break;

      case CUBEFACE_NEG_X:

    pos.x = dwf.max.x - positionInFace.y;
    pos.y = dwf.max.y - positionInFace.x;
    break;

      case CUBEFACE_POS_Y:

    pos.x = dwf.min.x + positionInFace.x;
    pos.y = dwf.max.y - positionInFace.y;
    break;

      case CUBEFACE_NEG_Y:

    pos.x = dwf.min.x + positionInFace.x;
    pos.y = dwf.min.y + positionInFace.y;
    break;

      case CUBEFACE_POS_Z:

    pos.x = dwf.max.x - positionInFace.x;
    pos.y = dwf.max.y - positionInFace.y;
    break;

      case CUBEFACE_NEG_Z:

    pos.x = dwf.min.x + positionInFace.x;
    pos.y = dwf.max.y - positionInFace.y;
    break;
    }

    return pos;
}


void
faceAndPixelPosition (const V3f &direction,
              const Box2i &dataWindow,
              CubeMapFace &face,
              V2f &pif)
{
    int sof = sizeOfFace (dataWindow);
    float absx = abs (direction.x);
    float absy = abs (direction.y);
    float absz = abs (direction.z);

    if (absx >= absy && absx >= absz)
    {
    if (absx == 0)
    {
        //
        // Special case - direction is (0, 0, 0)
        //

        face = CUBEFACE_POS_X;
        pif = V2f (0, 0);
        return;
    }

    pif.x = (direction.y / absx + 1) / 2 * (sof - 1);
    pif.y = (direction.z / absx + 1) / 2 * (sof - 1);

    if (direction.x > 0)
        face = CUBEFACE_POS_X;
    else
        face = CUBEFACE_NEG_X;
    }
    else if (absy >= absz)
    {
    pif.x = (direction.x / absy + 1) / 2 * (sof - 1);
    pif.y = (direction.z / absy + 1) / 2 * (sof - 1);

    if (direction.y > 0)
        face = CUBEFACE_POS_Y;
    else
        face = CUBEFACE_NEG_Y;
    }
    else
    {
    pif.x = (direction.x / absz + 1) / 2 * (sof - 1);
    pif.y = (direction.y / absz + 1) / 2 * (sof - 1);

    if (direction.z > 0)
        face = CUBEFACE_POS_Z;
    else
        face = CUBEFACE_NEG_Z;
    }
}


V3f
direction (CubeMapFace face, const Box2i &dataWindow, const V2f &positionInFace)
{
    int sof = sizeOfFace (dataWindow);

    V2f pos;

    if (sof > 1)
    {
    pos = V2f (positionInFace.x / (sof - 1) * 2 - 1,
           positionInFace.y / (sof - 1) * 2 - 1);
    }
    else
    {
    pos = V2f (0, 0);
    }

    V3f dir (1, 0, 0);

    switch (face)
    {
      case CUBEFACE_POS_X:

    dir.x = 1;
    dir.y = pos.x;
    dir.z = pos.y;
    break;

      case CUBEFACE_NEG_X:

    dir.x = -1;
    dir.y = pos.x;
    dir.z = pos.y;
    break;

      case CUBEFACE_POS_Y:

    dir.x = pos.x;
    dir.y = 1;
    dir.z = pos.y;
    break;

      case CUBEFACE_NEG_Y:

    dir.x = pos.x;
    dir.y = -1;
    dir.z = pos.y;
    break;

      case CUBEFACE_POS_Z:

    dir.x = pos.x;
    dir.y = pos.y;
    dir.z = 1;
    break;

      case CUBEFACE_NEG_Z:

    dir.x = pos.x;
    dir.y = pos.y;
    dir.z = -1;
    break;
    }

    return dir;
}

} // namespace CubeMap
} // namespace Imf