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我在動畫加載COLLADA模型時遇到了一些問題。我寫了自己的解析器，現在我也想編寫自己的繪製例程。問題在於，只要我在模型上啓用動畫，手，腿和頭部就會遠離模型的原點。 （加載器是基於這裏的教程實現的：COLLADA Tutorial）動畫COLLADA模型的動畫問題
我在模型的繪製函數中做的第一件事是用讀取塊的給定目標設置關節矩陣（不是世界矩陣！）， 如果我例如讀像一個信道：
<channel source="#some_sampler" target="some_joint/transform(3)(2)"/>
我將修改基質組分（3）（2）從接頭的jointMatrix與SID =在該第一步驟「改造」：
if(mCurrentAnimations_.size() > 0) {
unsigned currentFrame = GEAR::Root::getSingleton().getFrameEvent().frame;
bool updateTime = false;
if(currentFrame != mLastFrameUpdate_) {
if(timeSinceLastFrame < 1.0f)
updateTime = true;
mLastFrameUpdate_ = currentFrame;
}
/****************************************************
* If we have an active animation, *
* we animate it in each of it's defined channels *
***************************************************/
std::list<DAEAnimation*>::iterator it = mCurrentAnimations_.begin();
while(it != mCurrentAnimations_.end()) {
for(int c = 0; c < (*it)->animation->channels.size(); ++c) {
// update the time of the channelanimation if requested
if(updateTime) {
(*it)->channelStates[c].elapsedTime += timeSinceLastFrame;
}
GEAR::COLLADA::Channel* channel = (*it)->animation->channels[c];
// read the two indices depending on the time we're
int firstKeyframeTimeIndex = 0;
int secondKeyframeTimeIndex = 0;
for(int i = 0; i < channel->sampler->inputSource->mFloatArray_->mCount_; ++i) {
float time = channel->sampler->inputSource->mFloatArray_->mFloats_[i];
if(firstKeyframeTimeIndex == secondKeyframeTimeIndex && time > (*it)->channelStates[c].elapsedTime && i > 0) {
firstKeyframeTimeIndex = i-1;
secondKeyframeTimeIndex = i;
break;
}
if(firstKeyframeTimeIndex == secondKeyframeTimeIndex && i == channel->sampler->inputSource->mFloatArray_->mCount_-1) {
(*it)->channelStates[c].elapsedTime = 0.0f;
firstKeyframeTimeIndex = i;
secondKeyframeTimeIndex = 0;
break;
}
}
// look what kind of TargetAccessor we have
if(channel->targetAccessor != NULL && channel->targetAccessor->type == GEAR::MATRIX_ACCESSOR) {
// ok we have to read 1 value for first and second index
float firstValue = channel->sampler->outputSource->mFloatArray_->mFloats_[firstKeyframeTimeIndex];
float secondValue = channel->sampler->outputSource->mFloatArray_->mFloats_[secondKeyframeTimeIndex];
float firstTime = channel->sampler->inputSource->mFloatArray_->mFloats_[firstKeyframeTimeIndex];
float secondTime = channel->sampler->inputSource->mFloatArray_->mFloats_[secondKeyframeTimeIndex];
float interpolateValue = 1.0f/(secondTime - firstTime) * (secondTime - (*it)->channelStates[c].elapsedTime);
// now we calculate an linear interpolated value
float value = (secondValue*interpolateValue) + (firstValue*(1.0-interpolateValue));
// now we have to write this value to the Joint's Matrix
int entry = ((COLLADA::MatrixTargetAccessor*)channel->targetAccessor)->firstAccessor*4+((COLLADA::MatrixTargetAccessor*)channel->targetAccessor)->secondAccessor;
channel->targetJoint->matrix->jointSpaceMatrix.entries[entry] = channel->targetJoint->matrix->matrix.entries[entry] + value;
}
}
++it;
}
}
加入後
void
COLLADA::Joint::recalcWorldSpaceTransMat() {
GEAR::Mat4 parentMat;
if(parent != NULL)
parentMat = parent->worldSpaceTransformationMatrix;
// @todo Here we have to test against NULL!
if(matrix != NULL)
this->worldSpaceTransformationMatrix = parentMat * matrix->jointSpaceMatrix;
else {
this->worldSpaceTransformationMatrix = parentMat;
}
//std::cout << "Joint " << sid << " recalculated\n";
for(int i = 0; i < mChildJoints_.size(); ++i)
mChildJoints_[i]->recalcWorldSpaceTransMat();
}
現在一切都應該準備好繪製我的模型寬我的繪製函數的下列最後一部分：
tMatrices被所有渠道修改，我通過調用根關節以下功能重新計算關節的worldMatricesfor(int i = 0; i < mSubMeshes_.size(); ++i) {
for(int k = 0; k < mSubMeshes_[i]->mSubMeshes_.size(); ++k) {
// first we animate it
GEAR::DAESubMesh* submesh = mSubMeshes_[i]->mSubMeshes_[k];
submesh->buffer->lock(true);
{
for(unsigned v = 0; v < submesh->buffer->getNumVertices(); ++v) {
// get the array of joints, which influence the current vertex
DAEVertexInfo* vertexInfo = submesh->vertexInfo[v];
GEAR::Vec3 vertex; // do not init the vertex with any value!
float totalWeight = 0.0f;
for(int j = 0; j < vertexInfo->joints.size(); ++j) {
Mat4& invBindPoseMatrix = vertexInfo->joints[j]->joint->invBindPoseMatrix;
Mat4& transMat = vertexInfo->joints[j]->joint->worldSpaceTransformationMatrix;
totalWeight += vertexInfo->joints[j]->weight;
vertex += (transMat*invBindPoseMatrix*(submesh->skin->bindShapeMatrix*vertexInfo->vertex))*vertexInfo->joints[j]->weight;
}
if(totalWeight != 1.0f) {
float normalizedWeight = 1.0f/totalWeight;
vertex *= normalizedWeight;
}
submesh->buffer->bufferVertexPos(v, vertex);
}
}
submesh->buffer->unlock();
mSubMeshes_[i]->mSubMeshes_[k]->buffer->draw(GEAR::TRIANGLES, 0, mSubMeshes_[i]->mSubMeshes_[k]->buffer->getNumVertices());
}
}
現在的問題是，輸出如下所示： 
我敢肯定有正確執行的數據加載程序，因爲一般的動畫走的人是可見的，但絲網會變形： 
正如我所說的，當我取消對該行：
channel->targetJoint->matrix->jointSpaceMatrix.entries[entry] = channel->targetJoint->matrix->matrix.entries[entry] + value;
動畫是殘疾人和模型顯示在它的標準姿勢： 
現在除了當我添加一個正常化像這樣jointMatrices的第3列前，我重新計算關節的worldMatrix：
GEAR::Vec3 row1(matrix->jointSpaceMatrix.entries[0], matrix->jointSpaceMatrix.entries[1], matrix->jointSpaceMatrix.entries[2]);
row1.normalize();
matrix->jointSpaceMatrix.entries[0] = row1.x;
matrix->jointSpaceMatrix.entries[1] = row1.y;
matrix->jointSpaceMatrix.entries[2] = row1.z;
GEAR::Vec3 row2(matrix->jointSpaceMatrix.entries[4], matrix->jointSpaceMatrix.entries[5], matrix->jointSpaceMatrix.entries[6]);
row2.normalize();
matrix->jointSpaceMatrix.entries[4] = row2.x;
matrix->jointSpaceMatrix.entries[5] = row2.y;
matrix->jointSpaceMatrix.entries[6] = row2.z;
GEAR::Vec3 row3(matrix->jointSpaceMatrix.entries[8], matrix->jointSpaceMatrix.entries[9], matrix->jointSpaceMatrix.entries[10]);
row3.normalize();
matrix->jointSpaceMatrix.entries[8] = row3.x;
matrix->jointSpaceMatrix.entries[9] = row3.y;
matrix->jointSpaceMatrix.entries[10] = row3.z;
問題依然存在，但是這次在另一個輸出中。男人現在看起來像一個外星人：D，但這減少了縮放比例： 
我現在不完全是，我是否已經完成正常化的正確方法。這是否正常需要？它在教程中沒有描述，我也無法找到任何相關的東西。
畢竟我看了一下在教程頁面的代碼插值的實現。 AND：他們根本不使用任何四元數來插入孔矩陣。他們所做的就是以下（不工作對我來說）：
Mat4 temp;
for (int i = 0; i < 16; ++i)
temp.entries[i] = interpolatef(matrix->jointSpaceMatrixStart.entries[i],matrix->jointSpaceMatrixFinish.entries[i],matrix->delta);
Vec3 forward,up,right,translation;
forward = Vec3(temp.entries[8], temp.entries[9], temp.entries[10]);
up= Vec3(temp.entries[4], temp.entries[5], temp.entries[6]);
right = Vec3(temp.entries[0], temp.entries[1], temp.entries[2]);
forward.normalize();
up.normalize();
right.normalize();
temp.entries[8] = forward.x; temp.entries[9] = forward.y; temp.entries[10] = forward.z;
temp.entries[4] = up.x; temp.entries[5] = up.y; temp.entries[6] = up.z;
temp.entries[0] = right.x; temp.entries[1] = right.y; temp.entries[2] = right.z;
matrix->jointSpaceMatrix = GEAR::Mat4(temp);
然後我使用四元數在這樣的另一種方法（還沒有爲我的作品）：
// wat we need for interpolation: rotMatStart, rotMatFinish, delta
// create rotation matrices from our 2 given matrices
GEAR::Mat4 rotMatStart = matrix->jointSpaceMatrixStart;
rotMatStart.setTranslationPart(GEAR::VEC3_ZERO);
GEAR::Mat4 rotMatFinish = matrix->jointSpaceMatrixFinish;
rotMatFinish.setTranslationPart(GEAR::VEC3_ZERO);
rotMatStart.transpose();
rotMatFinish.transpose();
// create Quaternions, which represent these 2 matrices
float w = GEAR::Tools::sqr(1.0 + rotMatStart.entries[0] + rotMatStart.entries[5] + rotMatStart.entries[10])/2.0;
float w4 = (4.0 * w);
float x = (rotMatStart.entries[6] - rotMatStart.entries[9])/w4 ;
float y = (rotMatStart.entries[8] - rotMatStart.entries[2])/w4 ;
float z = (rotMatStart.entries[1] - rotMatStart.entries[4])/w4 ;
GEAR::Quaternion rotQuadStart(x, y, z, w);
rotQuadStart.normalize();
w = GEAR::Tools::sqr(1.0 + rotMatFinish.entries[0] + rotMatFinish.entries[5] + rotMatFinish.entries[10])/2.0;
w4 = (4.0 * w);
x = (rotMatFinish.entries[6] - rotMatFinish.entries[9])/w4 ;
y = (rotMatFinish.entries[8] - rotMatFinish.entries[2])/w4 ;
z = (rotMatFinish.entries[1] - rotMatFinish.entries[4])/w4 ;
GEAR::Quaternion rotQuadFinish(x, y, z, w);
rotQuadFinish.normalize();
// create the interpolated rotation matrix
GEAR::Quaternion slerpedRotQuat = slerp(rotQuadStart, rotQuadFinish, matrix->delta);
slerpedRotQuat.normalize();
GEAR::Mat4 rotMat;
slerpedRotQuat.createMatrix(rotMat);
// interpolate the translation part
GEAR::Vec3 transVecStart(0.0,0.0,0.0);
matrix->jointSpaceMatrixStart.getTranslatedVector3D(transVecStart);
GEAR::Vec3 transVecFinish(0.0,0.0,0.0);
matrix->jointSpaceMatrixFinish.getTranslatedVector3D(transVecFinish);
GEAR::Mat4 transMat;
transMat.setTranslation(transVecFinish*matrix->delta + (transVecStart*(1.0f-matrix->delta)));
// now write the resulting Matrix back to the Joint
matrix->jointSpaceMatrix = transMat * rotMat;
它也不會爲我工作。似乎沒有任何工作。我真的不知道這是怎麼回事。
現在後第2天，我得到了它的工作得益於datenwolf
我想告訴所有我得到了它的工作答案。現在一切都看起來很清楚，而且這一直只是一小步。 現在我們從動畫部分開始。我遍歷所有頻道並保存開始和結束值以及在範圍0.0 1.0到接頭的內插增量值，所述信道動畫：
if(mCurrentAnimations_.size() > 0) {
unsigned currentFrame = GEAR::Root::getSingleton().getFrameEvent().frame;
bool updateTime = false;
if(currentFrame != mLastFrameUpdate_) {
if(timeSinceLastFrame < 1.0f)
updateTime = true;
mLastFrameUpdate_ = currentFrame;
}
/****************************************************
* If we have an active animation, *
* we animate it in each of it's defined channels *
***************************************************/
std::list<DAEAnimation*>::iterator it = mCurrentAnimations_.begin();
while(it != mCurrentAnimations_.end()) {
for(int c = 0; c < (*it)->animation->channels.size(); ++c) {
// update the time of the channelanimation if requested
if(updateTime) {
(*it)->channelStates[c].elapsedTime += timeSinceLastFrame;
}
GEAR::COLLADA::Channel* channel = (*it)->animation->channels[c];
// read the two indices depending on the time we're
int firstIndex = 0;
int secondIndex = 1;
for(int i = 0; i < channel->sampler->inputSource->mFloatArray_->mCount_; ++i) {
float time = channel->sampler->inputSource->mFloatArray_->mFloats_[i];
if(time > (*it)->channelStates[c].elapsedTime) {
firstIndex = i-1;
secondIndex = i;
if(firstIndex == -1) // set to last frame
firstIndex = channel->sampler->inputSource->mFloatArray_->mCount_ - 1;
break;
}
else if(i == channel->sampler->inputSource->mFloatArray_->mCount_ - 1) {
(*it)->channelStates[c].elapsedTime -= channel->sampler->inputSource->mFloatArray_->mFloats_[i];
firstIndex = 0;
secondIndex = 1;
break;
}
}
// look what kind of TargetAccessor we have
if(channel->targetAccessor != NULL && channel->targetAccessor->type == GEAR::MATRIX_ACCESSOR) {
/************************************************************************
* Matrix accessors, which are read from a COLLADA <channel> block *
* will always target one matrix component they animate. *
* Such accessors are for example: *
* <channel source"#someSource" target="someJoint/transform(0)(2)"/> *
* *
* @TODO: *
* In a pre processing step, we have to group all channels, which *
* operate on the same joint. In order to accelerate the processing of *
* grouped channels, we have to expand the number of keyframes of all *
* channels to the maximum of all channels. *
************************************************************************/
unsigned entry = ((COLLADA::MatrixTargetAccessor*)channel->targetAccessor)->index;
float firstTime = channel->sampler->inputSource->mFloatArray_->mFloats_[firstIndex];
float secondTime = channel->sampler->inputSource->mFloatArray_->mFloats_[secondIndex];
// in case of matrix accessor, we write the startMatrix and the endMatrix to the Joints accessor, who finally will do the animation interpolation
channel->targetJoint->matrix->interpolationRequired = true;
// write out the start and end value to the jointSpaceMatrix
// this matrix will later be interpolated
channel->targetJoint->matrix->jointSpaceMatrixStart.entries[entry] = channel->sampler->outputSource->mFloatArray_->mFloats_[firstIndex];
channel->targetJoint->matrix->jointSpaceMatrixFinish.entries[entry] = channel->sampler->outputSource->mFloatArray_->mFloats_[secondIndex];
// the delta value is in the range [0.0,1.0]
channel->targetJoint->matrix->delta = 1.0f/(secondTime - firstTime) * (secondTime - (*it)->channelStates[c].elapsedTime);
}
}
++it;
}
}
正如可以看到，在這裏是沒有內插的。我們簡單地緩存所有動畫關節的開始和結束值以及增量（我們還在每個修改的關節上設置了一個標記）
所有動畫完成後，我們在所有根關節上調用函數interpolateMatrices（）：
for(int i = 0; i < mSourceModel_->mVisualSceneLibrary_.mVisualScenes_.size(); ++i) {
for(int v = 0; v < mSourceModel_->mVisualSceneLibrary_.mVisualScenes_[i]->mSkeleton_.size(); ++v) {
if(mSourceModel_->mVisualSceneLibrary_.mVisualScenes_[i]->mSkeleton_[v]->mRootJoint_ != NULL) {
/************************************************************************************
* Now we have constructed all jointSpaceMatrixces for the start and the end and *
* we're ready to interpolate them and to also recalculate the joint's *
* worldSpaceMatrix. *
***********************************************************************************/
mSourceModel_->mVisualSceneLibrary_.mVisualScenes_[i]->mSkeleton_[v]->mRootJoint_->interpolateMatrices();
}
}
}
這不是新的，但現在有趣的部分是插值的實現。沒有qith四元數都：
void COLLADA::Joint::interpolateMatrices() {
if(matrix != NULL && matrix->interpolationRequired) {
for (unsigned i = 0; i < 16; ++i)
matrix->jointSpaceMatrix.entries[i] = interpolatef(matrix->jointSpaceMatrixStart.entries[i],matrix->jointSpaceMatrixFinish.entries[i],matrix->delta);
Vec3 forward,up,right,translation;
forward = Vec3(matrix->jointSpaceMatrix.entries[8], matrix->jointSpaceMatrix.entries[9], matrix->jointSpaceMatrix.entries[10]);
up= Vec3(matrix->jointSpaceMatrix.entries[4], matrix->jointSpaceMatrix.entries[5], matrix->jointSpaceMatrix.entries[6]);
right = Vec3(matrix->jointSpaceMatrix.entries[0], matrix->jointSpaceMatrix.entries[1], matrix->jointSpaceMatrix.entries[2]);
forward.normalize();
up.normalize();
right.normalize();
matrix->jointSpaceMatrix.entries[8] = forward.x; matrix->jointSpaceMatrix.entries[9] = forward.y; matrix->jointSpaceMatrix.entries[10] = forward.z;
matrix->jointSpaceMatrix.entries[4] = up.x; matrix->jointSpaceMatrix.entries[5] = up.y; matrix->jointSpaceMatrix.entries[6] = up.z;
matrix->jointSpaceMatrix.entries[0] = right.x; matrix->jointSpaceMatrix.entries[1] = right.y; matrix->jointSpaceMatrix.entries[2] = right.z;
matrix->jointSpaceMatrix.entries[15] = 1.0f; // this component is always 1.0! In some files, this is exported the wrong way, which causes bugs!
}
/********************************************************
* After the interpolation is finished, *
* we have to recalculate the joint's worldSpaceMatrix. *
********************************************************/
GEAR::Mat4 parentMat;
if(parent != NULL)
parentMat = parent->worldSpaceTransformationMatrix;
if(matrix != NULL)
worldSpaceTransformationMatrix = (parentMat * matrix->jointSpaceMatrix);
else
worldSpaceTransformationMatrix = parentMat;
skinningMatrix = worldSpaceTransformationMatrix*invBindPoseMatrix;
// also interpolate and recalculate all childs
for(unsigned k = 0; k < mChildJoints_.size(); ++k)
mChildJoints_[k]->interpolateMatrices();
}
正如你可以看到，我們只是intrpolate矩陣，之後所有的值，我們正常化矩陣的上3列。 之後，我們立即重新計算該關節的worldSpaceMatrix，以及完整的蒙皮矩陣以節省性能。 現在我們幾乎完成了所有。最後要做的就是真正爲頂點設置動畫，然後繪製網格：
for(int i = 0; i < mSubMeshes_.size(); ++i) {
for(int k = 0; k < mSubMeshes_[i]->mSubMeshes_.size(); ++k) {
// first we animate it
GEAR::DAESubMesh* submesh = mSubMeshes_[i]->mSubMeshes_[k];
submesh->buffer->lock(true);
{
for(unsigned v = 0; v < submesh->buffer->getNumVertices(); ++v) {
// get the array of joints, which influence the current vertex
DAEVertexInfo* vertexInfo = submesh->vertexInfo[v];
GEAR::Vec3 vertex; // do not init the vertex with any value!
float totalWeight = 0.0f;
for(int j = 0; j < vertexInfo->joints.size(); ++j) {
totalWeight += vertexInfo->joints[j]->weight;
vertex += ((vertexInfo->joints[j]->joint->skinningMatrix*(vertexInfo->vertex))*vertexInfo->joints[j]->weight);
}
// since it isn't guaranteed that the total weight is exactly 1.0, we have no normalize it
// @todo this should be moved to the parser
if(totalWeight != 1.0f) {
float normalizedWeight = 1.0f/totalWeight;
vertex *= normalizedWeight;
}
submesh->buffer->bufferVertexPos(v, vertex);
}
}
submesh->buffer->unlock();
mSubMeshes_[i]->mSubMeshes_[k]->buffer->draw(GEAR::TRIANGLES, 0, mSubMeshes_[i]->mSubMeshes_[k]->buffer->getNumVertices());
}
}
總而言之，它與我開始使用的代碼幾乎相同。 但現在事情對我來說更加清晰了，我也可以開始支持<翻譯>,<輪換>和<規模>動畫也是如此。隨意看看我的實現在gear3d.de（下載SVN主幹）
我希望這可以幫助一些人在那裏實現自己的解決方案在這個美好的主題:)
+1;一個寫得很好的問題，給出了基本的代碼，並精確地描述了錯誤的和預期的正確結果。 – datenwolf