[osg-users] Show part of geometry which intersects a specific area

[Ali Ozdin]

Hi Robert,

Firstly, I am using osg 3.4.1. However I dont enable any GL_CLIP_PLANEi but all geometry in geodeForgeomRight works well except osgText geometries. Sample code is below:


Code:

osg::ClipNode* clipped_subgraph;
osg::ref_ptr<osg::Geode> geodeForgeomRight;

osg::ref_ptr<osgText::Text> bottomAltitudeText = new  osgText::Text;
osg::Vec3 position( (SCREEN_WIDTH * 0.64) + bigLineLength, (i/2)*lineBreak, 0.0f);
std::string timesFont("fonts/arial.ttf");
bottomAltitudeText->setAlignment(osgText::TextBase::AlignmentType::LEFT_CENTER);
bottomAltitudeText->setFont(timesFont);
bottomAltitudeText->setColor( osg::Vec4f(0.f, 255.f,0.f,1.f) );
bottomAltitudeText->setPosition(position);
bottomAltitudeText->setText("hello world" );
bottomAltitudeText->setCharacterSize(15.0);
geodeForgeomRight->addDrawable( bottomAltitudeText.get() );


osg::ref_ptr<osg::MatrixTransform> mt = new osg::MatrixTransform(); 
mt->addChild(geodeForgeomRight.get());

clipped_subgraph = new osg::ClipNode;
double xMin,yMin, zMin, xMax, yMax, zMax;
xMin = (SCREEN_WIDTH * 0.64);
yMin = SCREEN_HEIGHT*0.6 - 17*lineBreak;
zMin = 0.0f;
xMax = geodeForgeomRight.get()->getBoundingBox().xMax();
yMax = SCREEN_HEIGHT*0.6;
zMax = 0.0f;
osg::BoundingBox bb(xMin,yMin, zMin, xMax, yMax, zMax);
clipped_subgraph->createClipBox(bb);
clipped_subgraph->addChild(mt);

clipped_subgraph->setCullingActive(true);
mt->setUpdateCallback(new AltitudeCallBack());




Best regards, 


robertosfield wrote:
> Hi Ali,
> I haven't tested this specific combination of features, but in
> principle it should be just a case of enabling the GL_CLIP_PLANEi mode
> for the text subgraphs.
> 
> Which version of the OSG are you using and what GL versions?
> 
> The new osgText implementation in master/OSG-3.6 branch uses shaders
> so out of the box, looking at the shader I don't see any setting of
> the gl_ClipVertex so this could be a problem.  I will look into this.
> 
> Robert.
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