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DwD

triangle vertices from mesh.intersect

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using c# //Is it possible to extract the triangle vertices from mesh.intersect? if (yes) { how?; }

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yes.

you need a structure to represent a vertex. something like:

public struct PositionNormalTexVertex
{
public Vector3 Position;
public Vector3 Normal;
public float Tu0, Tv0;
public static readonly VertexFormats FVF = VertexFormats.Position |
VertexFormats.Texture1;
}

but you'll need to change it if your vertex declaration is different.

then lock the buffers and extract your info. i'll assume you've already created your ray and stuff:

//shoot ray
IntersectInformation intInf;
bool yup = m_mesh.Intersect(vPickRayOrig, vPickRayDir, out intInf);

PositionNormalTexVertex[] arr;
arr = new PositionNormalTexVertex[3];
if (yup)
{
//get streams to the buffers
VertexBuffer pVB;
IndexBuffer pIB;
pVB = m_mesh.VertexBuffer;
pIB = m_mesh.IndexBuffer;
GraphicsStream gsIB = pIB.Lock(0, 0, LockFlags.ReadOnly);
GraphicsStream gsVB = pVB.Lock(0, 0, LockFlags.ReadOnly);

//get pointers to the data
PositionNormalTexVertex* vbArray = (PositionNormalTexVertex*)gsVB.InternalDataPointer;
ushort* ibArray = (ushort*)gsIB.InternalDataPointer;

//get triangle indices
ushort i1, i2, i3;
i1 = ibArray[intInf.FaceIndex * 3 + 1];
i2 = ibArray[intInf.FaceIndex * 3 + 2];
i3 = ibArray[intInf.FaceIndex * 3 + 0];

//get triangle vertices
arr[0] = vbArray[i1];
arr[1] = vbArray[i2];
arr[2] = vbArray[i3];

//finished with the buffers
pIB.Unlock();
pVB.Unlock();
}


hope that helps,
n.

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Thanks,

I had thought I'd need to reference the vertexBuffer and indexBuffer but had no idea about a structure to represent the vertices.

I'm new to C# so I'll have to study this a bit, but I do think my answer is in there.

[EDIT]

yes, the answer is in there, but it's "unsafe". Is there anyway to do it with safe code?

[Edited by - DwD on March 2, 2006 7:48:39 AM]

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yes it's unsafe. i don't really know what that means tho :)
i just declare the function unsafe:

public unsafe Vector3 PickMesh(Matrix view, Vector3 ray)

maybe thats bad, i don't know, but it works fine.

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heh,

I'm not sure what it means either. Guess I'll have to look it up. I had already declared the method unsafe, just see that it worked.

I'm concerned it may cause trouble with publishing and one click security.

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