Mapping from polygon i + vertex j into corresponding UV from a UV Layer

[Anonymous]

I'm poosting this here a separate topic because I marked the other one as solved.

I've got the UV layer but now I'm having a different problem.

Doing...

FbxLayer* lUVLayer = pMesh->GetLayer(0, FbxLayerElement::eUV ) ; FbxLayerElementUV* leUV = lUVLayer->GetUVs();

I can see that the UVs are in there (just looking at the direct array), but I can't figure out how to index into it, having a polygon index and vertex index (within the polygon).

Mapping mode is FbxGeometryElement::eByPolygonVertex

and Reference mode is FbxGeometryElement::eIndexToDirect

The code that I had before did:

int uvidx = pMesh->GetTextureUVIndex(i,j);

int idx = aUV->GetIndexArray().GetAt(uvidx);

FbxVector2 rUV = aUV->GetDirectArray().GetAt(idx);

which works perfectly fine, but only for UVs in Layer 0.

That's because GetTextureUVIndex(i,j) only works for Layer 0.

I need the equivalent for this particular layer.

The following:

int ubidx = pMesh->GetPolygonVertex(i, j);

doesn't work.

So, how do I index into the uv vertex from a polygon index and a vertex position index ?

Thanks

[Anonymous · Accepted solution]

Got it...

I've found the following in the UVSample:

        else if (lUVElement->GetMappingMode() == FbxGeometryElement::eByPolygonVertex)
        {
            int lPolyIndexCounter = 0;
            for( int lPolyIndex = 0; lPolyIndex < lPolyCount; ++lPolyIndex )
            {
                // build the max index array that we need to pass into MakePoly
                const int lPolySize = pMesh->GetPolygonSize(lPolyIndex);
                for( int lVertIndex = 0; lVertIndex < lPolySize; ++lVertIndex )
                {
                    if (lPolyIndexCounter < lIndexCount)
                    {
                        FbxVector2 lUVValue;

                        //the UV index depends on the reference mode
                        int lUVIndex = lUseIndex ? lUVElement->GetIndexArray().GetAt(lPolyIndexCounter) : lPolyIndexCounter;

                        lUVValue = lUVElement->GetDirectArray().GetAt(lUVIndex);

                        //User TODO:
                        //Print out the value of UV(lUVValue) or log it to a file

                        lPolyIndexCounter++;
                    }
                }
            }
        }

Which shows that the equivalent for GetTextureUVIndex(i,j) reduces to

(i * 3 ) + j

in my triangular mesh example.

And in more general case it would be  vertexcount[0] + vertexcount[1] ... + vertexcount[i-1] + j

where vertexcount is the number of vertices in each polygon.

Best