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WS30: Improved algorithm for airport placement

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Previously the vertices directly underneath an airport were
displaced downwards.  In general this worked OK, but for airports
surrounded by higher terrain, this could cause "ridges" from
edges from vertices just outside the airport boundary.

This commit modifies the algorithm to also reduce the elevation
of vertices immediately outside the airport boundary as well.
This commit is contained in:
Stuart Buchanan
2022-02-24 22:29:34 +00:00
parent b157f9cb9f
commit 1a37dcf3d5
2 changed files with 37 additions and 18 deletions
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53
simgear/scene/tgdb/VPBTechnique.cxx
View File

@@ -537,11 +537,8 @@ void VertexNormalGenerator::populateCenter(osgTerrain::Layer* elevationLayer, os
if (validValue)
{
osg::Vec3d model;
osg::Vec3d origin;
_masterLocator->convertLocalToModel(osg::Vec3d(ndc.x(), ndc.y(), -1000), origin);
_masterLocator->convertLocalToModel(ndc, model);
model = VPBTechnique::checkAndDisplaceAgainstElevationConstraints(origin, model, _constraint_vtx_gap);
model = VPBTechnique::checkAndDisplaceAgainstElevationConstraints(ndc, _numColumns, _numRows, _constraint_vtx_gap, _masterLocator);
texcoords->push_back(osg::Vec2(ndc.x(), ndc.y()));
@@ -2382,23 +2379,45 @@ void VPBTechnique::removeElevationConstraint(osg::ref_ptr<osg::Node> constraint)
// Check a given vertex against any elevation constraints E.g. to ensure the terrain mesh doesn't
// poke through any airport meshes. If such a constraint exists, the function will return a replacement
// vertex displaces such that it lies 1m below the contraint relative to the passed in origin.
osg::Vec3d VPBTechnique::checkAndDisplaceAgainstElevationConstraints(osg::Vec3d origin, osg::Vec3d vertex, float vtx_gap)
// vertex displaces such that it below the contraint relative to the passed in origin by vtx_gap meters.
osg::Vec3d VPBTechnique::checkAndDisplaceAgainstElevationConstraints(osg::Vec3d ndc, int cols, int rows, float vtx_gap, Locator* masterLocator)
{
const std::lock_guard<std::mutex> lock(VPBTechnique::_elevationConstraintMutex); // Lock the _elevationConstraintGroup for this scope
osg::ref_ptr<osgUtil::LineSegmentIntersector> intersector;
intersector = new osgUtil::LineSegmentIntersector(origin, vertex);
osgUtil::IntersectionVisitor visitor(intersector.get());
_elevationConstraintGroup->accept(visitor);
if (intersector->containsIntersections()) {
// We have an intersection with our constraints model, so move the terrain vertex to 1m below the intersection point
osg::Vec3d ray = intersector->getFirstIntersection().getWorldIntersectPoint() - origin;
ray.normalize();
return intersector->getFirstIntersection().getWorldIntersectPoint() - ray*vtx_gap;
} else {
return vertex;
osg::Vec3d origin, vertex, deltaX, deltaY;
masterLocator->convertLocalToModel(osg::Vec3d(ndc.x(), ndc.y(), -1000), origin);
masterLocator->convertLocalToModel(ndc, vertex);
masterLocator->convertLocalToModel(ndc + osg::Vec3d(1.0 / (double) cols, 0.0,0.0), deltaX);
masterLocator->convertLocalToModel(ndc + osg::Vec3d(0.0, 1.0 / (double) rows, 0.0), deltaY);
double elev = ndc.z();
for (int i = -1; i < 2; ++i) {
for (int j = -1; j < 2; ++j) {
osg::Vec3d delta = deltaX * i + deltaY * j;
osg::ref_ptr<osgUtil::LineSegmentIntersector> intersector;
intersector = new osgUtil::LineSegmentIntersector(origin + delta, vertex + delta);
osgUtil::IntersectionVisitor visitor(intersector.get());
_elevationConstraintGroup->accept(visitor);
if (intersector->containsIntersections()) {
// We have an intersection with our constraints model, so move the terrain vertex to below the intersection point by vtx_gap meters
osg::Vec3d ray = intersector->getFirstIntersection().getWorldIntersectPoint() - (origin + delta);
ray.normalize();
osg::Vec3d local;
masterLocator->convertModelToLocal(intersector->getFirstIntersection().getWorldIntersectPoint() - ray*vtx_gap, local);
if (elev > local.z()) {
elev = local.z();
}
}
}
}
// elev now contains the local elevation of a point constrained by the elevation constraints of the vertex and the 8 surrounding
// vertices.
osg::Vec3d constrained;
masterLocator->convertLocalToModel(osg::Vec3d(ndc.x(), ndc.y(), elev), constrained);
return constrained;
}
bool VPBTechnique::checkAgainstElevationConstraints(osg::Vec3d origin, osg::Vec3d vertex)

2
simgear/scene/tgdb/VPBTechnique.hxx
View File

@@ -96,7 +96,7 @@ class VPBTechnique : public TerrainTechnique
// As airports are generated in a separate loading thread, these are static.
static void addElevationConstraint(osg::ref_ptr<osg::Node> constraint);
static void removeElevationConstraint(osg::ref_ptr<osg::Node> constraint);
static osg::Vec3d checkAndDisplaceAgainstElevationConstraints(osg::Vec3d origin, osg::Vec3d vertex, float vertex_gap);
static osg::Vec3d checkAndDisplaceAgainstElevationConstraints(osg::Vec3d ndc, int cols, int rows, float vtx_gap, Locator* masterLocator);
static bool checkAgainstElevationConstraints(osg::Vec3d origin, osg::Vec3d vertex);
static void clearConstraints();