point normals

Helper

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On 16/03/2010 at 09:21, xxxxxxxx wrote:

User Information:
Cinema 4D Version:   r11
Platform:
Language(s) :     C++ ;

---------
hi there,

how can i create a normal direction for a point? i suppose that i need to calculate the sum of the normals of all polygons which use that point and than divide it by the number of polygons used. but 1. how do i find out which polygons use a certain point and 2. would that be a performance issue (if i would cycle thru all polygons for every point and check if the point is used by that polygon)?

thanks and cheers,
ello

Helper

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On 16/03/2010 at 16:42, xxxxxxxx wrote:

Howdy,

Have a look at the Neighbor class.

Adios,
Cactus Dan

Helper

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On 16/03/2010 at 22:44, xxxxxxxx wrote:

Thank you! Thats exactly what i need

cheers,
Ello

Helper

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On 18/03/2010 at 11:48, xxxxxxxx wrote:

Of course you could also just let C4D tell you what they are - look at: PolygonObject::CreatePhongNormals() - the advantage to that is that phong-break edges are also taken into account.

Cheers,

Keith

Helper

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On 18/03/2010 at 13:24, xxxxxxxx wrote:

thank you.. now i did this:

  
Vector n;  
Vector* phongNormal = myMesh->CreatePhongNormals();  
for (int i=0;i<pointcount;i++)  
{  
n=phongNormal[i] _;  
}

Is there anything wrong with my assumption that this should return the normal for point i ? somehow it looks a bit screwed up..

thanks for your input,
ello
_

Helper

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On 18/03/2010 at 13:48, xxxxxxxx wrote:

CreatePhongNormals() creates normals for each of a polygon's points. For a cube for instance it will create 6*4 point normals. This is necessary to describe phong breaks. Depending on what you want to achieve this is maybe not really what you are looking for. I am guessing that you are looking for a way to obtain average point normals, right?

cheers,
Matthias

Helper

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On 18/03/2010 at 13:52, xxxxxxxx wrote:

yes, exactly.. so do you think i should go the way using the Neighbours ?

Helper

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On 19/03/2010 at 01:04, xxxxxxxx wrote:

Well you can still use CreatePhongNormals() and average these normals for each point.

-build the point normals per polygon array with CreatePhongNormals()
-iterate through all the points, GetPointR(), GetPointCount()
-get the adjacent polygons for each point with GetPointPolys()
-for each adjacent polygon get the point normal for the common point
-average these normals

alternatively
-iterate through all the points, GetPointR(), GetPointCount()
-get the adjacent polygons for each point with GetPointPolys()
-calculate the polygon normal for each adjacent polygon (or create an polygon normal array in advance)
-average these normals

Since there is no "correct" way you have to try which works better for you.

cheers,
Matthias

Helper

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On 19/03/2010 at 01:29, xxxxxxxx wrote:

thank you.. after looking again at my code i found why i got that error message. i wrote Neighbour instead of Neighbor..

kind regards,
ello

Helper

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On 19/03/2010 at 12:38, xxxxxxxx wrote:

Hi, i am still having a problem here.

  
                  neighbor.GetPointPolys(i,&dadr,&dcnt);  
                  GePrint(LongToString(dcnt));

dcnt is always 0, but how can this be? there are actually quite a lot of points and polygons in the base mesh..
i dont understand this.

thanks for any input.
cheers,
ello

Helper

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On 19/03/2010 at 12:49, xxxxxxxx wrote:

Sorry these two lines of code don't say much Please post a bigger portion of your code, for instance how you initialized the Neighbor class.

cheers,
Matthias

Helper

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On 19/03/2010 at 12:58, xxxxxxxx wrote:

oh, ok.. i placed the neighbor.Init(...) in a condition which wasnt true..
it works now. thanks for all your help

cheers,
ello

Helper

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On 11/06/2010 at 09:42, xxxxxxxx wrote:

hi again,

i am still struggling and i thought before further hijacking the other thread i bring this thead up again:

here is my code for averaging.. polygonNormal returns the right polygon normals, as seen in this screen:

  
  
      padr = cloneOfBase->GetPointR();  
      pol = cloneOfBase->GetPolygonR();  
      numberofclones = cloneOfBase->GetPointCount();  
      maxcount = cloneOfBase->GetPolygonCount();  
...  
  
              if (neighbor.Init(numberofclones, pol, maxcount, NULL))  
              {  
                  neighbor.GetPointPolys(i, &dadr, &dcnt);  
                  if (dcnt)  
                  {  
                      for (int j=0;j<dcnt;j++)  
                      {  
                          if (dadr[j]<=maxcount)  
                          {  
                              polyNormal += polygonNormal(nCalc1,nCalc2,padr,pol,dadr[j]);  
                          }  
                      }  
                      polyNormal /= dcnt;  
                  }  
              }

any ideas??

cheers,
ello

Helper

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On 11/06/2010 at 10:18, xxxxxxxx wrote:

I see that you're still not normalizing the result of polygonNormal() or of polyNormal, after you've divided it... have you tried that?

Helper

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On 11/06/2010 at 10:25, xxxxxxxx wrote:

yes, that gave me even stranger results. what i dont understand is that it works for most of the points

Helper

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On 11/06/2010 at 11:30, xxxxxxxx wrote:

Ok, here is some verified working code that I've stripped out to be stand-alone callable routines...

  
//---------------------------------------------------------------------------------------   
//***************************************************************************************   
// GetVertexNormals()   
//***************************************************************************************   
//---------------------------------------------------------------------------------------   
Vector *GetVertexNormals(PolygonObject *pObj)   
{   
     LONG numVerts = pObj->GetPointCount();   
     LONG numPolys = pObj->GetPolygonCount();   
     const Vector *pVerts = pObj->GetPointR();   
     const CPolygon *pPolys = pObj->GetPolygonR();   
  
     // initialize neighbor class... this is used to compute m_SrcvNorms   
     Neighbor neighbor;   
     if( !neighbor.Init(numVerts, pPolys, numPolys, NULL) )   
          return NULL;   
  
     // Allocate array of Normal Vectors to fill in and return   
     Vector *pNormals = (Vector * )GeAlloc(numVerts * sizeof(Vector));   
     if( !pNormals )     return NULL;   
  
     // Determine a Normal for each vertex of mesh   
     LONG i, j, faceCnt, *pFaces = NULL;   
     Vector vNorm;   
     for(i=0; i<numVerts; i++)   
     {   
          vNorm = Vector();          // (re)intitialize   
          neighbor.GetPointPolys(i, &pFaces;, &faceCnt;);   
          if( faceCnt )   
          {   
               for(j=0; j<faceCnt; j++)   
               {   
                    Vector n = CalcFaceNormal(pVerts, pPolys[pFaces[j]]);   
                    vNorm += !n;   
               }   
               vNorm /= faceCnt;          // average the normal(s)   
               pNormals[i] = !vNorm;     // normalize and store   
          }   
          else   
               pNormals[i] = Vector(0.0,1.0,0.0);     // default case = Up for any stray verts   
     }   
     return pNormals;   
}   
  
//---------------------------------------------------------------------------------------   
//***************************************************************************************   
// AddNormSplineObject()   
//***************************************************************************************   
//---------------------------------------------------------------------------------------   
void AddNormSplineObject(PolygonObject *pObj, LONG splineLen)   
{   
     Vector *pNormals = GetVertexNormals(pObj);   
     if( !pNormals )     return;   
  
     LONG numNorms = pObj->GetPointCount();   
  
     // allocate spline object large enough for all points   
     SplineObject *splineOp = SplineObject::Alloc(2*numNorms,Tlinear);   
     if( !splineOp || !splineOp->MakeVariableTag(Tsegment,numNorms) )   
     {   
          MessageDialog(String("Spline Object Allocation Failed"));   
          GeFree(pNormals);   
          return;   
     }   
     splineOp->SetName(String("NormSplines"));   
  
     Vector *padr = splineOp->GetPointW();   
     Segment *sadr = splineOp->GetSegmentW();   
  
     if( !padr || !sadr )   
     {   
          MessageDialog(String("Spline Object Data Setup Failed"));   
          GeFree(pNormals);   
          SplineObject::Free(splineOp);   
          return;   
     }   
  
     const Vector *pVerts = pObj->GetPointR();   
     Matrix mg = pObj->GetMgn();   
     LONG normCnt = 0;   
     LONG vertCnt = 0;   
     LONG i;   
     for(i=0; i<numNorms; i++)   
     {   
          sadr[normCnt].cnt = 2;   
          sadr[normCnt++].closed = false;   
  
          padr[vertCnt++] = pVerts[i] * mg;   
          padr[vertCnt++] = (pVerts[i] + (pNormals[i] * splineLen)) * mg;   
     }   
     splineOp->GetDataInstance()->SetBool(SPLINEOBJECT_CLOSED,false);   
  
     GeFree(pNormals); // done with this now   
  
     BaseDocument *pBaseDoc = pObj->GetDocument();   
     pBaseDoc->InsertObject(splineOp,NULL,NULL);   
     splineOp->Message(MSG_UPDATE);   
}

...just cut/paste that into your code and call the AddNormSplineObject() routine with your PolygonObject. Once you've verified that it's working, you can either use it as-is, or reference it to figure out why yours is not working.

Helper

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On 11/06/2010 at 11:31, xxxxxxxx wrote:

If you have any compile errors or trouble with include files, let me know.

Helper

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On 11/06/2010 at 12:08, xxxxxxxx wrote:

thank you very much.. after first crash, i passed my doc to the function like this,
void AddNormSplineObject(PolygonObject *pObj, LONG splineLen,BaseDocument *doc)

and it works.. now i need to understand why it does

again, thank you very very much for your help!

cheers,
ello

Helper

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On 11/06/2010 at 12:14, xxxxxxxx wrote:

D'oh! I guess that your PolygonObject wasn't yet attached to the scene :). I usually test all results before using pointers like that, but I kinda threw that in there at the last minute when I was stripping out my old Class member code.

Anyway... if you want, you can just use that GetVertexNormals() routine as-is (just be sure to GeFree() the array when you're done with it).

Good luck!

Helper

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On 11/06/2010 at 12:18, xxxxxxxx wrote:

i now used the pNormals to rotate my clones and now it looks like when i told you how it looked after i used the normalised normals:

any idea? how can this be?? i'll have to recheck my code after the rotation. i just dont understand why it works for polygons, but not for points. very strange