[osg-users] Writing texture coordinates on a mesh without going through traversal code?

[Robert Osfield]

HI Marlin,

I would hope that you can implement what you need without getting your
hands dirty with internals of the OSG. It sound like you want something
similar to osg::ClipPlaneNode.  Have a look at osgclip to see how it works.

Robert.

On 13 April 2018 at 22:30, Rowley, Marlin R <marlin.r.rowley at lmco.com>
wrote:

> Hello!
>
>
>
> I’m trying to generate my own texture coordinates (on-the-fly) by having a
> callback that runs when a piece of geometry intersects my object.  So for
> example, I create a realworld frustum and when my frustum has a shader
> that’s bound to some arbitrary object in the world.  When my frustum
> intersects this object, I would like to generate texture coordinates on
> this object based on how far or near I am to the frustum’s near/far planes
> (it’s perspective frustum).  We had the following code for doing this:
>
>
>
> void ViewshedOSG::updateTextureCoordinates()
>
> {
>
> // write the plane equation for all 3 planes
>
> // that make up the camera view frustum.  We can
>
> // then access this from the shader to test whether
>
> // we are in the frustum's volume or not.
>
>     osg::Matrixd projection = mCamera->getViewMatrix();
>
>       mTexGen->setPlanesFromMatrix(projection *
>
>       osg::Matrix::translate(1.0, 1.0, 1.0) *
>
>       osg::Matrix::scale(0.5f, 0.5f, 0.5f));
>
> // Bring our models viewspace coordinates back
>
> // into model space coordinate of the camera frustum
>
> osg::RefMatrix * refMatrix = new osg::RefMatrix
>
>            (mCamera->getInverseViewMatrix() * *_cv->getModelViewMatrix());
>
> // Copy the texture generator to the mesh where you
>
> // can index it's coordinates from the ViewshedID
>
>       _cv->getRenderStage()->getPositionalStateContainer()->
>
>             addPositionedTextureAttribute
>
>             (mId, refMatrix, mTexGen.get());
>
> }
>
>
>
>
>
> However, this code was based on a cull visitor calling this function from
> a callback.  I have my own callback and it’s not based on a visitor. Is
> there anyway to get the objects modelview matrix() without calling it from
> a cull visitor?  Also only need to write the ‘addPositionedTextureAttribute’
> on the geometry in order to access the coordinates through a shader.
>
>
>
> I’m trying to keep this simple.  Am I in the right direction?
>
>
>
> Thanks,
>
>
>
> -M
>
> ----------------------------------------
>
> Marlin Rowley
>
> Software Engineer, Staff
>
> [image: cid:image002.jpg at 01D39374.DEC5A2E0]
>
> *Missiles and Fire Control*
>
> 972-603-1931 (office)
>
> 214-926-0622 (mobile)
>
> marlin.r.rowley at lmco.com
>
>
>
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