osgEarth的Rex引擎原理分析（七十一）

目标：（五十五）中的问题142

1、在RexTerrainEngineNode遍历时生成renderleaf，其中的drawable为LayerDrawable（其对应earth文件中每一个高程、影像层）。在TerrainCuller进行遍历时，会对LayerDrawable添加实际瓦片对应的高程影像纹理，这样绘制出来就能看到高程影像效果了。

osgEarthDrivers/engine_rex/RexTerrainEngineNode.cpp
void
RexTerrainEngineNode::dirtyState()
{
    LayerDrawable* lastLayer = 0L;
    for(LayerDrawableList::iterator i = culler._terrain.layers().begin();
            i != culler._terrain.layers().end();
            ++i)
    {
        lastLayer = i->get();
        cv->apply(*lastLayer);
    }
}

osgUtil/RenderLeaf
inline RenderLeaf(osg::Drawable* drawable,osg::RefMatrix* projection,osg::RefMatrix* modelview, float depth=0.0f, unsigned int traversalOrderNumber=0):
            osg::Referenced(false),
            _parent(0),
            _drawable(drawable),
            _projection(projection),
            _modelview(modelview),
            _depth(depth),
            _traversalOrderNumber(traversalOrderNumber)
        {
            _dynamic = (drawable->getDataVariance()==osg::Object::DYNAMIC);
        }

2、在渲染时从renderleaf中取出drawable进行绘制，此时会用到顶点着色器，对顶点位置进行设置，对高程进行设置的着色器代码为RexEngine.Elevation.glsl(它里面调用了RexEngine.SDK.vert.glsl的函数)

osgEarthDrivers/engine_rex/LayerDrawable.cpp
void
LayerDrawable::drawImplementation(osg::RenderInfo& ri) const
{
    for (DrawTileCommands::const_iterator tile = _tiles.begin(); tile != _tiles.end(); ++tile)
    {
        tile->draw(ri, *_drawState, 0L);
    }
}

osgEarthDrivers/engine_rex/DrawTileCommand.cpp
void
DrawTileCommand::draw(osg::RenderInfo& ri, DrawState& dsMaster, osg::Referenced* layerData) const
{
    _geom->render(ptype, ri);
}

osgEarthDrivers/engine_rex/GeometryPool.cpp
void SharedGeometry::render(GLenum primitiveType, osg::RenderInfo& renderInfo) const
{
    //调用opengl进行绘制，并进入图形管线
    glDrawElements(primitiveType, _drawElements->getNumIndices(), _drawElements->getDataType(), (const GLvoid *)(ebo->getOffset(_drawElements->getBufferIndex())));
}

 

 

 

 

 

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标签：Rex,const,void,rex,osgEarth,LayerDrawable,drawable,七十一,osg
来源： https://blog.csdn.net/hankern/article/details/104192146