code/Common/TargetAnimation.cpp

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Open Asset Import Library (assimp)
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*/

#include "TargetAnimation.h"
#include <assimp/ai_assert.h>
#include <algorithm>

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
KeyIterator::KeyIterator(const std::vector<aiVectorKey> *_objPos,
    const std::vector<aiVectorKey> *_targetObjPos,
    const aiVector3D *defaultObjectPos /*= nullptr*/,
    const aiVector3D *defaultTargetPos /*= nullptr*/) :
        reachedEnd(false),
        curTime(-1.),
        objPos(_objPos),
        targetObjPos(_targetObjPos),
        nextObjPos(0),
        nextTargetObjPos(0) {
    // Generate default transformation tracks if necessary
    if (!objPos || objPos->empty()) {
        defaultObjPos.resize(1);
        defaultObjPos.front().mTime = 10e10;

        if (defaultObjectPos)
            defaultObjPos.front().mValue = *defaultObjectPos;

        objPos = &defaultObjPos;
    }
    if (!targetObjPos || targetObjPos->empty()) {
        defaultTargetObjPos.resize(1);
        defaultTargetObjPos.front().mTime = 10e10;

        if (defaultTargetPos)
            defaultTargetObjPos.front().mValue = *defaultTargetPos;

        targetObjPos = &defaultTargetObjPos;
    }
}

// ------------------------------------------------------------------------------------------------
template <class T>
inline T Interpolate(const T &one, const T &two, ai_real val) {
    return one + (two - one) * val;
}

// ------------------------------------------------------------------------------------------------
void KeyIterator::operator++() {
    // If we are already at the end of all keyframes, return
    if (reachedEnd) {
        return;
    }

    // Now search in all arrays for the time value closest
    // to our current position on the time line
    double d0, d1;

    d0 = objPos->at(std::min(nextObjPos, static_cast<unsigned int>(objPos->size() - 1))).mTime;
    d1 = targetObjPos->at(std::min(nextTargetObjPos, static_cast<unsigned int>(targetObjPos->size() - 1))).mTime;

    // Easiest case - all are identical. In this
    // case we don't need to interpolate so we can
    // return earlier
    if (d0 == d1) {
        curTime = d0;
        curPosition = objPos->at(nextObjPos).mValue;
        curTargetPosition = targetObjPos->at(nextTargetObjPos).mValue;

        // increment counters
        if (objPos->size() != nextObjPos - 1)
            ++nextObjPos;

        if (targetObjPos->size() != nextTargetObjPos - 1)
            ++nextTargetObjPos;
    }

    // An object position key is closest to us
    else if (d0 < d1) {
        curTime = d0;

        // interpolate the other
        if (1 == targetObjPos->size() || !nextTargetObjPos) {
            curTargetPosition = targetObjPos->at(0).mValue;
        } else {
            const aiVectorKey &last = targetObjPos->at(nextTargetObjPos);
            const aiVectorKey &first = targetObjPos->at(nextTargetObjPos - 1);

            curTargetPosition = Interpolate(first.mValue, last.mValue, (ai_real)((curTime - first.mTime) / (last.mTime - first.mTime)));
        }

        if (objPos->size() != nextObjPos - 1)
            ++nextObjPos;
    }
    // A target position key is closest to us
    else {
        curTime = d1;

        // interpolate the other
        if (1 == objPos->size() || !nextObjPos) {
            curPosition = objPos->at(0).mValue;
        } else {
            const aiVectorKey &last = objPos->at(nextObjPos);
            const aiVectorKey &first = objPos->at(nextObjPos - 1);

            curPosition = Interpolate(first.mValue, last.mValue, (ai_real)((curTime - first.mTime) / (last.mTime - first.mTime)));
        }

        if (targetObjPos->size() != nextTargetObjPos - 1)
            ++nextTargetObjPos;
    }

    if (nextObjPos >= objPos->size() - 1 &&
            nextTargetObjPos >= targetObjPos->size() - 1) {
        // We reached the very last keyframe
        reachedEnd = true;
    }
}

// ------------------------------------------------------------------------------------------------
void TargetAnimationHelper::SetTargetAnimationChannel(
        const std::vector<aiVectorKey> *_targetPositions) {
    ai_assert(nullptr != _targetPositions);

    targetPositions = _targetPositions;
}

// ------------------------------------------------------------------------------------------------
void TargetAnimationHelper::SetMainAnimationChannel(
        const std::vector<aiVectorKey> *_objectPositions) {
    ai_assert(nullptr != _objectPositions);

    objectPositions = _objectPositions;
}

// ------------------------------------------------------------------------------------------------
void TargetAnimationHelper::SetFixedMainAnimationChannel(
        const aiVector3D &fixed) {
    objectPositions = nullptr; // just to avoid confusion
    fixedMain = fixed;
}

// ------------------------------------------------------------------------------------------------
void TargetAnimationHelper::Process(std::vector<aiVectorKey> *distanceTrack) {
    ai_assert(nullptr != targetPositions);
    ai_assert(nullptr != distanceTrack);

    // TODO: in most cases we won't need the extra array
    std::vector<aiVectorKey> real;

    std::vector<aiVectorKey> *fill = (distanceTrack == objectPositions ? &real : distanceTrack);
    fill->reserve(std::max(objectPositions->size(), targetPositions->size()));

    // Iterate through all object keys and interpolate their values if necessary.
    // Then get the corresponding target position, compute the difference
    // vector between object and target position. Then compute a rotation matrix
    // that rotates the base vector of the object coordinate system at that time
    // to match the diff vector.

    KeyIterator iter(objectPositions, targetPositions, &fixedMain);
    for (; !iter.Finished(); ++iter) {
        const aiVector3D &position = iter.GetCurPosition();
        const aiVector3D &tposition = iter.GetCurTargetPosition();

        // diff vector
        aiVector3D diff = tposition - position;
        ai_real f = diff.Length();

        // output distance vector
        if (f) {
            fill->push_back(aiVectorKey());
            aiVectorKey &v = fill->back();
            v.mTime = iter.GetCurTime();
            v.mValue = diff;

            diff /= f;
        } else {
            // FIXME: handle this
        }

        // diff is now the vector in which our camera is pointing
    }

    if (real.size()) {
        *distanceTrack = real;
    }
}