assimp/tools/assimp_view/AnimEvaluator.cpp

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#include "assimp_view.h"

using namespace AssimpView;

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

// ------------------------------------------------------------------------------------------------
// 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) ? mLastPositions[a].get<0>() : 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;
			}

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

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

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

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

	mLastTime = time;
}