osg示例解析之osganimationskinning

来源：互联网发布：广东省政府网络问政编辑：程序博客网时间：2024/05/04 17:28

转载原文网址 http://blog.csdn.net/csxiaoshui/article/details/22814373

简介

osgAnimationSkinning这个示例主要使用了osgAnimation中的骨骼蒙皮动画，关于骨骼蒙皮动画的介绍可以参考Skinned Mesh原理解析和一个最简单的实现示例这篇CSDN的博客，里面用Glut实现了一个简单的蒙皮动画，整篇文章对骨骼动画和蒙皮进行了详尽的阐述，相信读完之后可以对骨骼动画有更深的理解。

示例

源码中createAxis创建了一个坐标系，代码十分的简单，仅仅是画出三条坐标轴线而已。

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osg::Geode* createAxis()  
{  
    osg::Geode* geode (new osg::Geode());  
    osg::Geometry* geometry (new osg::Geometry());  
  
    osg::Vec3Array* vertices (new osg::Vec3Array());  
    vertices->push_back (osg::Vec3 ( 0.0, 0.0, 0.0));  
    vertices->push_back (osg::Vec3 ( 1.0, 0.0, 0.0));  
    vertices->push_back (osg::Vec3 ( 0.0, 0.0, 0.0));  
    vertices->push_back (osg::Vec3 ( 0.0, 1.0, 0.0));  
    vertices->push_back (osg::Vec3 ( 0.0, 0.0, 0.0));  
    vertices->push_back (osg::Vec3 ( 0.0, 0.0, 1.0));  
    geometry->setVertexArray (vertices);  
  
    osg::Vec4Array* colors (new osg::Vec4Array());  
    colors->push_back (osg::Vec4 (1.0f, 0.0f, 0.0f, 1.0f));  
    colors->push_back (osg::Vec4 (1.0f, 0.0f, 0.0f, 1.0f));  
    colors->push_back (osg::Vec4 (0.0f, 1.0f, 0.0f, 1.0f));  
    colors->push_back (osg::Vec4 (0.0f, 1.0f, 0.0f, 1.0f));  
    colors->push_back (osg::Vec4 (0.0f, 0.0f, 1.0f, 1.0f));  
    colors->push_back (osg::Vec4 (0.0f, 0.0f, 1.0f, 1.0f));  
    geometry->setColorArray (colors, osg::Array::BIND_PER_VERTEX);  
    geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINES,0,6));  
  
    geode->addDrawable( geometry );  
    return geode;  
}  

createTesselatedBox这个函数做的是创建了骨骼动画的蒙皮Mesh，相当于给骨骼做了一件“衣服”，我们看看它怎么创建的：

[cpp] view plaincopy
float step = size / static_cast<float>(nsplit);  
float s = 0.5f/4.0f;  
for (int i = 0; i < nsplit; i++)  
{  
    float x = -1.0f + static_cast<float>(i) * step;  
    std::cout << x << std::endl;  
    vertices->push_back (osg::Vec3 ( x, s, s));  
    vertices->push_back (osg::Vec3 ( x, -s, s));  
    vertices->push_back (osg::Vec3 ( x, -s, -s));  
    vertices->push_back (osg::Vec3 ( x, s, -s));  
    osg::Vec3 c (0.0f,0.0f,0.0f);  
    c[i%3] = 1.0f;  
    colors->push_back (c);  
    colors->push_back (c);  
    colors->push_back (c);  
    colors->push_back (c);  
}  
  
osg::ref_ptr<osg::UIntArray> array = new osg::UIntArray;  
for (int i = 0; i < nsplit - 1; i++)  
{  
    int base = i * 4;  
  
    //Top  
    array->push_back(base);  
    array->push_back(base+1);  
    array->push_back(base+4);  
    array->push_back(base+1);  
    array->push_back(base+5);  
    array->push_back(base+4);  
  
    //Back  
    array->push_back(base+3);  
    array->push_back(base);  
    array->push_back(base+4);  
    array->push_back(base+7);  
    array->push_back(base+3);  
    array->push_back(base+4);  
  
    //Front  
    array->push_back(base+5);  
    array->push_back(base+1);  
    array->push_back(base+2);  
    array->push_back(base+2);  
    array->push_back(base+6);  
    array->push_back(base+5);  
  
    //Bottom  
    array->push_back(base+2);  
    array->push_back(base+3);  
    array->push_back(base+7);  
    array->push_back(base+6);  
    array->push_back(base+2);  
    array->push_back(base+7);  
}  

通过上面的注解可以知道，函数createTesselatedBox(int nsplit, float size)的两个参数，其中nsplit是把这个立方体柱分成了nsplit-1段，然后每段一个立方体的4个面，这段代码使用的是DrawElement的方式创建的，因此它传入的是索引值。

接下来就是Skin info的操作，给不同的顶点绑定到骨骼上，并且给这些顶点赋予权值，这个示例中设置权值的方式比较简单，所有X在-1到0之间的顶点只受到骨骼Bon0的影响，所有X在0到1之间的顶点只受Bone1的影响，所有X值大于1的顶点只受到Bone2的影响。

[cpp] view plaincopy
void initVertexMap(osgAnimation::Bone* b0,  
                   osgAnimation::Bone* b1,  
                   osgAnimation::Bone* b2,  
                   osgAnimation::RigGeometry* geom,  
                   osg::Vec3Array* array)  
{  
    //osgAnimation::VertexInfluenceSet vertexesInfluences;  
    osgAnimation::VertexInfluenceMap* vim = new osgAnimation::VertexInfluenceMap;  
  
    (*vim)[b0->getName()].setName(b0->getName());  
    (*vim)[b1->getName()].setName(b1->getName());  
    (*vim)[b2->getName()].setName(b2->getName());  
  
    for (int i = 0; i < (int)array->size(); i++)  
    {  
        float val = (*array)[i][0];  
        std::cout << val << std::endl;  
        if (val >= -1.0f && val <= 0.0f)  
            (*vim)[b0->getName()].push_back(osgAnimation::VertexIndexWeight(i,1.0f));  
        else if ( val > 0.0f && val <= 1.0f)  
            (*vim)[b1->getName()].push_back(osgAnimation::VertexIndexWeight(i,1.0f));  
        else if ( val > 1.0f)  
            (*vim)[b2->getName()].push_back(osgAnimation::VertexIndexWeight(i,1.0f));  
    }  
  
    geom->setInfluenceMap(vim);  
}  

主函数main里面主要创建了骨骼动画：

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osg::ref_ptr<osgAnimation::Skeleton> skelroot = new osgAnimation::Skeleton;  
skelroot->setDefaultUpdateCallback();  
osg::ref_ptr<osgAnimation::Bone> root = new osgAnimation::Bone;  
root->setInvBindMatrixInSkeletonSpace(osg::Matrix::inverse(osg::Matrix::translate(-1.0,0.0,0.0)));  
root->setName("root");  
osgAnimation::UpdateBone* pRootUpdate = new osgAnimation::UpdateBone("root");  
pRootUpdate->getStackedTransforms().push_back(new osgAnimation::StackedTranslateElement("translate",osg::Vec3(-1.0f,0.0f,0.0f)));  
root->setUpdateCallback(pRootUpdate);  
  
osg::ref_ptr<osgAnimation::Bone> right0 = new osgAnimation::Bone;  
right0->setInvBindMatrixInSkeletonSpace(osg::Matrix::inverse(osg::Matrix::translate(0.0,0.0,0.0)));  
right0->setName("right0");  
osgAnimation::UpdateBone* pRight0Update = new osgAnimation::UpdateBone("right0");  
pRight0Update->getStackedTransforms().push_back(new osgAnimation::StackedTranslateElement("translate", osg::Vec3(1.0f,0.0f,0.0f)));  
pRight0Update->getStackedTransforms().push_back(new osgAnimation::StackedRotateAxisElement("rotate", osg::Vec3(0.0f,0.0f,1.0f), 0.0));  
right0->setUpdateCallback(pRight0Update);  
  
osg::ref_ptr<osgAnimation::Bone> right1 = new osgAnimation::Bone;  
right1->setInvBindMatrixInSkeletonSpace(osg::Matrix::inverse(osg::Matrix::translate(1.0,0.0,0.0)));  
right1->setName("right1");  
osgAnimation::UpdateBone* pRight1Update = new osgAnimation::UpdateBone("right1");  
pRight1Update->getStackedTransforms().push_back(new osgAnimation::StackedTranslateElement("translate", osg::Vec3(1.0f,0.0f,0.0f)));  
pRight1Update->getStackedTransforms().push_back(new osgAnimation::StackedRotateAxisElement("rotate", osg::Vec3(0.0f,0.0f,1.0f), 0.0));  
right1->setUpdateCallback(pRight1Update);  
  
root->addChild(right0.get());  
right0->addChild(right1.get());  
skelroot->addChild(root.get());  

以上代码创建了骨骼的框架，这个创建骨骼的模式还是比较固定的，需要注意的是UpdateBone的名称需要和下面Channel的SetTargetName名称一致，UpdateBone里面StackedTransformElement需要和Channel的Name一致

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osg::Group* scene = new osg::Group;  
osg::ref_ptr<osgAnimation::BasicAnimationManager> manager = new osgAnimation::BasicAnimationManager;  
scene->setUpdateCallback(manager.get());  
  
osgAnimation::Animation* anim = new osgAnimation::Animation;  
{  
    osgAnimation::FloatKeyframeContainer* keys0 = new osgAnimation::FloatKeyframeContainer;  
    keys0->push_back(osgAnimation::FloatKeyframe(0.0,0.0f));  
    keys0->push_back(osgAnimation::FloatKeyframe(3.0,osg::PI_2));  
    keys0->push_back(osgAnimation::FloatKeyframe(6.0,osg::PI_2));  
    osgAnimation::FloatLinearSampler* sampler = new osgAnimation::FloatLinearSampler;  
    sampler->setKeyframeContainer(keys0);  
    osgAnimation::FloatLinearChannel* channel = new osgAnimation::FloatLinearChannel(sampler);  
    channel->setName("rotate");  
    channel->setTargetName("right0");  
    anim->addChannel(channel);  
}  
  
{  
    osgAnimation::FloatKeyframeContainer* keys1 = new osgAnimation::FloatKeyframeContainer;  
    keys1->push_back(osgAnimation::FloatKeyframe(0.0,0.0f));  
    keys1->push_back(osgAnimation::FloatKeyframe(3.0,0.0f));  
    keys1->push_back(osgAnimation::FloatKeyframe(6.0,osg::PI_2));  
    osgAnimation::FloatLinearSampler* sampler = new osgAnimation::FloatLinearSampler;  
    sampler->setKeyframeContainer(keys1);  
    osgAnimation::FloatLinearChannel* channel = new osgAnimation::FloatLinearChannel(sampler);  
    channel->setName("rotate");  
    channel->setTargetName("right1");  
    anim->addChannel(channel);  
}  
manager->registerAnimation(anim);  
//manager->buildTargetReference();  
  
// let's start !  
manager->playAnimation(anim);  

这段代码创建了骨骼动画运行的关键帧。

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osg::MatrixTransform* rootTransform = new osg::MatrixTransform;  
rootTransform->setMatrix(osg::Matrix::rotate(osg::PI_2,osg::Vec3(1.0f,0.0f,0.0f)));  
right0->addChild(createAxis());  
right0->setDataVariance(osg::Object::DYNAMIC);  
right1->addChild(createAxis());  
right1->setDataVariance(osg::Object::DYNAMIC);  
osg::MatrixTransform* trueroot = new osg::MatrixTransform;  
trueroot->setMatrix(osg::Matrix(root->getMatrixInBoneSpace().ptr()));  
trueroot->addChild(createAxis());  
trueroot->addChild(skelroot.get());  
trueroot->setDataVariance(osg::Object::DYNAMIC);  
rootTransform->addChild(trueroot);  
scene->addChild(rootTransform);  

上面的这段代码把可绘制实体添加到骨骼动画之中，这样我们才能看见骨骼动画的实际效果。这些Geode将抽象的骨骼变换具体化，能让我们看见Geode上面绑定着的骨骼的运动效果。

最后一步当然是进行骨骼动画的蒙皮操作了，将蒙皮Mesh设置好与骨骼的绑定以及权值之后，将这个节点添加到Skeleton节点之下就可以了：

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osgAnimation::RigGeometry* geom = createTesselatedBox(4, 4.0f);  
osg::Geode* geode = new osg::Geode;  
geode->addDrawable(geom);  
skelroot->addChild(geode);  
osg::ref_ptr<osg::Vec3Array> src = dynamic_cast<osg::Vec3Array*>(geom->getSourceGeometry()->getVertexArray());  
geom->getOrCreateStateSet()->setMode(GL_LIGHTING, false);  
geom->setDataVariance(osg::Object::DYNAMIC);  
  
initVertexMap(root.get(), right0.get(), right1.get(), geom, src.get());  

最后编译运行程序

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osg示例解析之osganimationskinning

简介

示例