Hi Mike
Hi,
I am wanting to do a dust cloud when an entity (helicopter) lands on a terrain. Ideally,
would like the color of the dust cloud to be similar to the material/texture that the
entity is on. Is there a way to do a "material/texture color" query based on an
entity position, kind of like an LOS intersector test?
Thank you!
You can use the osgUtil::LineSegmentIntersector to retrieve intersections.
The result will contain the information on the primitives hit, so you
can get the stateset containing the material properties from there. As
for the textures: you can also retrieve the texel you hit.
I've attached some code-snippet out of some test-application of mine.
<snip>
if (!mExternalPickPositionHandler.empty() && computeIntersections(view,
ea, intersections) )
{
osg::Vec3d pos = (intersections.begin())->getWorldIntersectPoint();
osg::Vec3d normal =
(intersections.begin())->getWorldIntersectNormal();
#ifdef TEST_TEXELS
// use the nearest intersection
const osgUtil::LineSegmentIntersector::Intersection&
intersection = *(intersections.begin());
osg::Drawable* drawable = intersection.drawable.get();
osg::Geometry* geometry = drawable ? drawable->asGeometry() : 0;
osg::Vec3Array* vertices = geometry ?
dynamic_cast<osg::Vec3Array*>(geometry->getVertexArray()) : 0;
if (vertices)
{
// get the vertex indices.
const
osgUtil::LineSegmentIntersector::Intersection::IndexList& indices =
intersection.indexList;
const
osgUtil::LineSegmentIntersector::Intersection::RatioList& ratios =
intersection.ratioList;
if (indices.size()==3 && ratios.size()==3)
{
unsigned int i1 = indices[0];
unsigned int i2 = indices[1];
unsigned int i3 = indices[2];
float r1 = ratios[0];
float r2 = ratios[1];
float r3 = ratios[2];
osg::Array* texcoords =
(geometry->getNumTexCoordArrays()>0) ? geometry->getTexCoordArray(0) : 0;
osg::Vec2Array* texcoords_Vec2Array =
dynamic_cast<osg::Vec2Array*>(texcoords);
if (texcoords_Vec2Array)
{
osg::Vec2 tc1 = (*texcoords_Vec2Array)[i1];
osg::Vec2 tc2 = (*texcoords_Vec2Array)[i2];
osg::Vec2 tc3 = (*texcoords_Vec2Array)[i3];
osg::Vec2 tc = tc1*r1 + tc2*r2 + tc3*r3;
//normalize, since negative tex-coords are not
handled by osg::Image::set/getImage
float int_part;
if (tc[0] < 0) { tc[0] = 1.0 - modf(tc[0],
&int_part); }
if (tc[1] < 0) { tc[1] = 1.0 - modf(tc[1],
&int_part); }
osg::Texture* texture =
intersection.getTextureLookUp(osg::Vec3(tc,0));
osg::Image* image = nullptr;
if (texture && (image = texture->getImage(0)))
{
osg::Vec4 color = image->getColor(osg::Vec3(tc,0));
std::cout << SCRed() << "HIT texture: " <<
image->getFileName() << " at " << color << std::endl;
image->setColor(osg::Vec4(color) *
0.9,osg::Vec3(tc,0));
image->dirty();
texture->setDataVariance(osg::Object::DYNAMIC);
}
}
}
}
</snip>
Cheers,
Mike
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=64857#64857
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