PxHeightfield::getTriangleMaterial seems unusable from the outside

Gaming and Visualization Technologies APIs Physics Modeling (closed)
1

I need the normal at a grid point on the heightfield.

I can already query the height with PxHeightfield::getHeight(x,z) and I could also draft a normal using multiple sample points. However, I want the normal to match whatever PhysX uses internally and don’t want to reproduce all the internal normal code. I also can’t due to several other functions not being exposed.

There is PxHeightfield::getTriangleNormal, which is perfect, but there seems to be no public way of mapping from grid co-ordinates to heightfield triangle ID.

There is physx::Gu::Heightfield::getTriangleIndex(x,z) which would solve all my issues but that’s not publicly exposed.

Is there any other way of getting the triangle normal other than adding a virtual forwarding call from PxHeightfield to getTriangleIndex?

Thanks,

  • Don
2

Title should be getTriangleNormal, of course.

3

It should be easy to add missing functions to the heightfield API. I’ll add an internal task for this.

Now, HeightField::getTriangleIndex(x,z) is one thing, but I also see we have a HeightFieldUtil::getNormalAtShapePoint(x,z) that might be exactly what you want.

4

Thanks.

I’m using PhysX via UE4 right now and as far as I can see, no UE4 code uses physx::Gu::HeightFieldUtil. The header file is in the Source directory rather than the Include directory so I was unsure as to getNormalAtShapePoint’s accessibility.

My workaround right now is to add a differently-named getTriangleID to PxHeightfield as I don’t want the existing implementation to suddenly inherit the cost of the virtual call.

5

Ok good, if you have a workaround already I’ll just schedule this task as usual and the change should eventually appear in UE4.

Otherwise tell me and I can probably help create a temporary function to retrieve the normal.

6

All is good right now! The function is marked to be removed when any API updates come through.

7

Hi Pierre_Terdiman.

I have stumbled upon similar issue.
I need to retrieve the heightfield normal at given row/column, but the above problem makes me unable to do so.

Also, is it just me or Gu::Heightfield is not usable outside?
I get include errors in PhysX classes (in this case at GuHeightfield at the top includes) when I try to include directory.

dwilliamson any chance to share your solution?

Any help would be appreciated.
Thanks.

8

Ok, I think I get it now. :P
So Gu::Heightfield etc are for internal use only.
In case you are fine with building PhysX sources, here’s what you can do to retrieve the heightfield vertex normal:

PxHeightField.h

/**
\brief Returns vertex normal at vertex index or sample id (row * nbCols + Col)

\return Vertex normal vector
*/
PX_PHYSX_COMMON_API virtual	PxVec3 getVertNormal(PxU32 vertIndex, const class PxHeightFieldGeometry& hfGeom) const = 0;

GuHeightField.h

PX_PHYSX_COMMON_API virtual PxVec3 getVertNormal(PxU32 vertIndex, const class PxHeightFieldGeometry& hfGeom) const;

GuHeightField.cpp

#include "GuHeightFieldUtil.h"

PxVec3 Gu::HeightField::getVertNormal(PxU32 vertIndex, const PxHeightFieldGeometry & hfGeom) const
{
    Gu::HeightFieldUtil hfUtil(hfGeom, *this);
    return hfUtil.getVertexNormal(vertIndex);
}

Then, from your project, you can simply do something like:

// Get the heightfield geometry from the heightfield shape
PxHeightFieldGeometry Geom;
gShape->getHeightFieldGeometry(Geom);

// Compute sample id
const uint32 SampleId = InRow * gHfNbCols + InColumn;

// Get the normal
const PxVec3 SampleNormal = gHeightField->getVertNormal(SampleId, Geom);

// Using UE4 here so, things are a little switched
return FVector(SampleNormal.z, SampleNormal.x, SampleNormal.y);

Would be nice if something like that could be introduced in the API by default.
Nelson Duarte,
Thanks!