SOP with only vertex attribute ?

[nicholas_yue]

Hi,

 

  I am prototyping a SOP which generates UVs (2D) using a sampling algorithm

 

  Here is what I did in the cook

  (1) clearAndDestroy()

  (2) appendVertexBlock(nSamples)

  (3) addFloatTuple(GA_ATTRIB_VERTEX, "suv", 2)

  (4) getVertexRange() // for use subsequently

  (5) set up UT_ValArray<fpreal32> suvResult

  (6) append data via suvResult.append(resultIter->x) in a loop

  finally

  (7) setAttributeFromArray(suvAttrib,vertexRange,suvResult)

 

  When I look at the SOP's spreadsheet, I can see the rows matches nSamples but they are all empty

 

  Is that because vertex need to reference a point (Point Num) so I'd have to add at least a dummy point ?

 

  How would one associate (programmatically) a vertex to the point ?

 

 

Cheers

 

[edward]

I don't know that the spreadsheet looks at unattached vertices at all. By definition, a vertex is a "point reference that resides in a primitive". See here for the typical polygon case:

http://www.sidefx.com/docs/hdk13.0/_h_d_k__geometry__intro.html#HDK_GeometryIntro_AddingPrimitive

[nicholas_yue]

I don't know that the spreadsheet looks at unattached vertices at all. By definition, a vertex is a "point reference that resides in a primitive". See here for the typical polygon case:

http://www.sidefx.com/docs/hdk13.0/_h_d_k__geometry__intro.html#HDK_GeometryIntro_AddingPrimitive

 

Thanks for that Edward, using that example code as a based, I created a dummy primitive with a single dummy point and added all the sampling UV vertex attribute with all the vertices referencing the same single point and the UV data shows up

 

        prim_poly_ptr->appendVertex(first_ptoff)

 

Cheers