I do not understand why you has so much problem trying to secund guess how
ndShapeStatic_bvh works.
that collision shape is designed to take an unstructured array of polygons, where each polygon is an array of vertices that falls on a flat plane. The polygons can be concave.
the class will find out all the information, adjacency, normal and topology.
It will remove degenerate faces and edges,
It will make a Delaney triangular mesh to make each triangle area maximal.
It will optimize flat adjacent phases into large faces if possible.
it will from convex partitions to removed contact across flat edges.
and will make adjacency. and so on.
there is a lot going on, on that class.
So yes, the index list will be very different that when you pass in.
if you want to make a custom collision shape similar but using different algorithm because you have your all method, that is quite possible, but you are going the wrong way.
you have four options.
The base class for static mesh is class. ndShapeStaticMesh
the engine implements three subclasses: ndShapeStatic_bvh, ndShapeHeightfield and ndShapeStaticProceduralMesh
deriving or changing ndShapeStatic_bvh and do not recommend and in fact will be a no, no
because it goes against object objective programing.
deriving from ndShapeHeightfield is non sensical because height filed capitalize on the regular organization of a 2d array of elevation, so it knows fow to make the intersecting faces.
so you are left with two options.
the easiest is to subclass from ndShapeStaticProceduralMesh
this class already provide some of the support function that will be requires if you derive from
ndShapeStaticMesh directly. stuff like ray casting, convex cast, support vertex, multiread queries, and so on, you only need to implement one method.
the more advanced option is to derive from ndShapeStaticMesh, and you will have to do all the work implementing support functions.
This probably makes sense for some special classes of geometries, liek it seems it is you case.
an example would be stuff like iso surfaces, or meshes when everything is very unique.
my suggestion is that is you want to make a shape like the ndShapeStatic_bvh
you sub class from ndShapeStaticMesh and copy and paste the code from ndShapeStatic_bvh
that will give you and class that you can experiment with and build your adjacency the way you think is best. that way you do not have to respect how the engine class does it now, and you can use whatever you think is useful to your class.
unlike Newton 3.14 that new shapes required registration, newton 4 only requires that a new shape is subclass from one of the archetypes: ndShapeConvex or ndShapeStaticMesh
for example, the code to make a flat plane collision shape is this
- Code: Select all
ndBodyKinematic* BuildFlatPlane(ndDemoEntityManager* const scene, bool optimized)
{
ndPhysicsWorld* const world = scene->GetWorld();
ndVector floor[] =
{
{ 200.0f, 0.0f, 200.0f, 1.0f },
{ 200.0f, 0.0f, -200.0f, 1.0f },
{ -200.0f, 0.0f, -200.0f, 1.0f },
{ -200.0f, 0.0f, 200.0f, 1.0f },
};
ndInt32 index[][3] = { { 0, 1, 2 },{ 0, 2, 3 } };
ndPolygonSoupBuilder meshBuilder;
meshBuilder.Begin();
meshBuilder.AddFaceIndirect(&floor[0].m_x, sizeof(ndVector), 31, &index[0][0], 3);
meshBuilder.AddFaceIndirect(&floor[0].m_x, sizeof(ndVector), 31, &index[1][0], 3);
meshBuilder.End(optimized);
ndShapeInstance plane(new ndShapeStatic_bvh(meshBuilder));
nowhere is assume indices order, normal or adjacency.
the code to make the same flat plane procedural, would be this
- Code: Select all
ndBodyKinematic* BuildProceduralMap(ndDemoEntityManager* const scene, ndInt32 grids, ndFloat32 gridSize, ndFloat32 perturbation)
{
ndPlane planeEquation(ndVector(0.0f, 1.0f, 0.0f, 0.0f));
ndShapeInstance plane(new ndRegularProceduralGrid(gridSize, 2.0f * grids * gridSize, 1.0f, 2.0f * grids * gridSize, planeEquation));
you see that ndRegularProceduralGrid is a shape make on the application side for demonstration. and that class is designed in file
.../newton-4.00\applications\ndSandbox\toolbox\ndMakeProceduralStaticMap.cpp line 22
I do not know how else to make it clearer.
