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Animating ASSIMP models

David · 2013-05-27T14:08:40

I'm using open asset importer to try and animate a model (Trying CPU animation). While the file is being parsed, i build up a skeleton: for (int i = 0; i < m_vSkeleton.size(); ++i) { Joint& joint = m_vSkeleton; if (joint.Parent() == -1) { joint.Working() = BuildMatrix(joint.Rotation(), joint.Translation()); } else { joint.Working() = BuildMatrix(joint.Rotation(), joint.Translation()) * m_vSkeleton[joint.Parent()].Working(); } } At this point if i render the skeleton it displays fine. I then load the translation and rotation frames for (int i = 0; i < scene->mNumAnimations; ++i) { aiAnimation* animation = scene->mAnimations; for (int j = 0; j < animation->mNumChannels; ++j) { aiNodeAnim* channel = animation->mChannels[j]; Joint& joint = m_vSkeleton[skeletonMap[channel->mNodeName.data]]; for (int k = 0; k < channel->mNumRotationKeys; ++k) { aiQuatKey* rotationKey = &channel->mRotationKeys[k]; joint.RotationTrack().push_back(RotationFrame()); RotationFrame& frame = joint.RotationTrack()[joint.RotationTrack().size() - 1]; frame.time = float(rotationKey->mTime); frame.rotation = Quaternion(rotationKey->mValue.w, rotationKey->mValue.x, rotationKey->mValue.y, rotationKey->mValue.z); } // k for (int k = 0; k < channel->mNumPositionKeys; ++k) { aiVectorKey* positionKey = &(channel->mPositionKeys[k]); joint.TranslationTrack().push_back(TranslationFrame()); TranslationFrame& frame = joint.TranslationTrack()[joint.TranslationTrack().size() - 1]; frame.time = float(positionKey->mTime); frame.translation = Vector(positionKey->mValue.x, positionKey->mValue.y, positionKey->mValue.z); frame.translation.w = 1.0f; } // k } // j totalDuration += float(animation->mDuration); numFrames += float(animation->mDuration * animation->mTicksPerSecond); playbackSpeed += float(animation->mTicksPerSecond); } // i Finally, i animate the skeleton: void Animation::ArticulateSkeletonToClip(float deltaTime) { if (m_nPlayback > m_pCurrentAnimation->m_nDuration) { if (m_pCurrentAnimation->m_nPlaybackMode == AnimationClip::kPlaybackLoop) { m_nPlayback -= m_pCurrentAnimation->m_nDuration; } } else m_nPlayback += deltaTime; m_nPlayback = 0.0f; for (int i = 0; i < m_vSkeleton.size(); ++i) { Joint& joint = m_vSkeleton; if (joint.TranslationTrack().size() == 0 && joint.RotationTrack().size() == 0) continue; Matrix localTransform = BuildMatrix(joint.Rotation(), joint.Translation()); Vector animatedTranslation; Quaternion animatedRotation; // Find the translation frame number int frame = m_pCurrentAnimation->m_nStartFrame; while (frame < m_pCurrentAnimation->m_nEndFrame && joint.TranslationTrack()[frame].time < m_nPlayback) ++frame; if (frame > m_pCurrentAnimation->m_nEndFrame) frame = m_pCurrentAnimation->m_nEndFrame; // Interpolate translation if (frame == m_pCurrentAnimation->m_nStartFrame) { // No prev frame animatedTranslation = joint.TranslationTrack()[m_pCurrentAnimation->m_nStartFrame].translation; } else if (frame == m_pCurrentAnimation->m_nEndFrame) { // No "this" frame animatedTranslation = joint.TranslationTrack()[frame - 1].translation; } else { // Do the actual interpolation TranslationFrame& curFrame = joint.TranslationTrack()[frame]; TranslationFrame& prevFrame = joint.TranslationTrack()[frame - 1]; float timeDelta = curFrame.time - prevFrame.time; float interpValue = (float)((m_nPlayback - prevFrame.time) / timeDelta); animatedTranslation = Lerp(prevFrame.translation, curFrame.translation, interpValue); } // Find the rotation frame frame = 0; while (frame < m_pCurrentAnimation->m_nEndFrame && joint.RotationTrack()[frame].time < m_nPlayback) ++frame; if (frame > m_pCurrentAnimation->m_nEndFrame) frame = m_pCurrentAnimation->m_nEndFrame; // Interpolate rotation if (frame == m_pCurrentAnimation->m_nStartFrame) { // No prev frame animatedRotation = joint.RotationTrack()[m_pCurrentAnimation->m_nStartFrame].rotation; } else if (frame == m_pCurrentAnimation->m_nEndFrame) { // No "this" frame animatedRotation = joint.RotationTrack()[frame - 1].rotation; } else { // Do actual interpolation RotationFrame& curFrame = joint.RotationTrack()[frame]; RotationFrame& prevFrame = joint.RotationTrack()[frame - 1]; float timeDelta = curFrame.time - prevFrame.time; float interpValue = (float)((m_nPlayback - prevFrame.time) / timeDelta); animatedRotation = Slerp(prevFrame.rotation, curFrame.rotation, interpValue); } // Animate the bone in local space Matrix animationTransform = BuildMatrix(animatedRotation, animatedTranslation); localTransform = animationTransform * localTransform; if (joint.Parent() == -1) { joint.Working() = localTransform; } else { joint.Working() = localTransform * m_vSkeleton[joint.Parent()].Working(); } } } However, rendering at this point the skeleton looks way wrong. I think the rotation / translation tracks are not working the way i think they are. Maybe they are the absolute world position, or something like that? I'm having a super hard time finding any information on the topic. Does anyone have any experience with this?