Re: [osg-news] Trail

[Robert O. <ro...@op...>]

Hi Tommy,

On Saturday 24 May 2003 23:37, Tommy Persson wrote:
 > What is the best way to implement a trail in OSG?  In performer I
 > cloned a node and used a SCS node to put it in the correct position.
 >
 > My current version in OSG is:
 >
 > void Trail::updateFrom(const osg::Vec3 & pos,
 >                      const osg::Vec3 & fdir,
 >                      const osg::Vec3 & udir) {
 >
 >   Witas::Visualizer::DirectionMatrixTransform* tmat =
 >     new Witas::Visualizer::DirectionMatrixTransform;
 >   tmat->moveTo (pos);
 >   tmat->setOrientation (fdir, udir);
 >   tmat->addChild (trailShape);
 >   trail->addChild(tmat);
 > }
 >
 > where trailShape is a pointer to a Drawable node and
 > DirectionMatrixTransform inherits from MatrixTransform.  But this
 > implemtation ha a noticable slow down in performance.  The trailShape
 > was a cone.

Is the trail shape a single cone or a seperate cone for each update 
position?  
 From the code above it looks like a seperate cone per position.

What you could do is use a series of osg::Shape's, the can be positioned 
and
orientated via an quaternion so would avoid the need for the transform 
which
will be adding over head to cull and draw traversals.    There is a Cone
shape in the list of Shapes.  Have a look at the osgshape example for code
for setting it up.

If peformance really needs to be optimized then I'd consider a custom 
Drawable
for managing a list of Vec3 + osg::Quat for the trail, then custom drawing
code to render the trail as required.

Robert.