assimp/tools/assimp_view/AnimEvaluator.cpp

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#include "assimp_view.h"

#include <tuple>

using namespace AssimpView;

// ------------------------------------------------------------------------------------------------
// Constructor on a given animation.
AnimEvaluator::AnimEvaluator( const aiAnimation *pAnim )
: mAnim(pAnim)
, mLastTime(0.0) {
    mLastPositions.resize( pAnim->mNumChannels, std::make_tuple( 0, 0, 0));
}

// ------------------------------------------------------------------------------------------------
// Destructor.
AnimEvaluator::~AnimEvaluator() {
    // empty
}

// ------------------------------------------------------------------------------------------------
// Evaluates the animation tracks for a given time stamp.
void AnimEvaluator::Evaluate( double pTime ) {
    // extract ticks per second. Assume default value if not given
    double ticksPerSecond = mAnim->mTicksPerSecond != 0.0 ? mAnim->mTicksPerSecond : 25.0;
    // every following time calculation happens in ticks
    pTime *= ticksPerSecond;

    // map into anim's duration
    double time = 0.0f;
    if (mAnim->mDuration > 0.0) {
        time = fmod(pTime, mAnim->mDuration);
    }

    if (mTransforms.size() != mAnim->mNumChannels) {
        mTransforms.resize(mAnim->mNumChannels);
    }

    // calculate the transformations for each animation channel
    for( unsigned int a = 0; a < mAnim->mNumChannels; ++a ) {
        const aiNodeAnim* channel = mAnim->mChannels[a];

        // ******** Position *****
        aiVector3D presentPosition( 0, 0, 0);
        if( channel->mNumPositionKeys > 0) {
            // Look for present frame number. Search from last position if time is after the last time, else from beginning
            // Should be much quicker than always looking from start for the average use case.
            unsigned int frame = (time >= mLastTime) ? std::get<0>(mLastPositions[a]) : 0;
            while( frame < channel->mNumPositionKeys - 1) {
                if (time < channel->mPositionKeys[frame + 1].mTime) {
                    break;
                }
                ++frame;
            }

            // interpolate between this frame's value and next frame's value
            unsigned int nextFrame = (frame + 1) % channel->mNumPositionKeys;
            const aiVectorKey& key = channel->mPositionKeys[frame];
            const aiVectorKey& nextKey = channel->mPositionKeys[nextFrame];
            double diffTime = nextKey.mTime - key.mTime;
            if (diffTime < 0.0) {
                diffTime += mAnim->mDuration;
            }
            if( diffTime > 0) {
                float factor = float( (time - key.mTime) / diffTime);
                presentPosition = key.mValue + (nextKey.mValue - key.mValue) * factor;
            } else {
                presentPosition = key.mValue;
            }

            std::get<0>(mLastPositions[a]) = frame;
        }

        // ******** Rotation *********
        aiQuaternion presentRotation( 1, 0, 0, 0);
        if( channel->mNumRotationKeys > 0) {
            unsigned int frame = (time >= mLastTime) ? std::get<1>(mLastPositions[a]) : 0;
            while( frame < channel->mNumRotationKeys - 1) {
                if (time < channel->mRotationKeys[frame + 1].mTime) {
                    break;
                }
                ++frame;
            }

            // interpolate between this frame's value and next frame's value
            unsigned int nextFrame = (frame + 1) % channel->mNumRotationKeys;
            const aiQuatKey& key = channel->mRotationKeys[frame];
            const aiQuatKey& nextKey = channel->mRotationKeys[nextFrame];
            double diffTime = nextKey.mTime - key.mTime;
            if (diffTime < 0.0) {
                diffTime += mAnim->mDuration;
            }
            if( diffTime > 0) {
                float factor = float( (time - key.mTime) / diffTime);
                aiQuaternion::Interpolate( presentRotation, key.mValue, nextKey.mValue, factor);
            } else {
                presentRotation = key.mValue;
            }

            std::get<1>(mLastPositions[a]) = frame;
        }

        // ******** Scaling **********
        aiVector3D presentScaling( 1, 1, 1);
        if( channel->mNumScalingKeys > 0) {
            unsigned int frame = (time >= mLastTime) ? std::get<2>(mLastPositions[a]) : 0;
            while( frame < channel->mNumScalingKeys - 1) {
                if (time < channel->mScalingKeys[frame + 1].mTime) {
                    break;
                }
                ++frame;
            }

            // TODO: (thom) interpolation maybe? This time maybe even logarithmic, not linear
            presentScaling = channel->mScalingKeys[frame].mValue;
            std::get<2>(mLastPositions[a]) = frame;
        }

        // build a transformation matrix from it
        aiMatrix4x4& mat = mTransforms[a];
        mat = aiMatrix4x4( presentRotation.GetMatrix());
        mat.a1 *= presentScaling.x; mat.b1 *= presentScaling.x; mat.c1 *= presentScaling.x;
        mat.a2 *= presentScaling.y; mat.b2 *= presentScaling.y; mat.c2 *= presentScaling.y;
        mat.a3 *= presentScaling.z; mat.b3 *= presentScaling.z; mat.c3 *= presentScaling.z;
        mat.a4 = presentPosition.x; mat.b4 = presentPosition.y; mat.c4 = presentPosition.z;
    }

    mLastTime = time;
}