Problem using Reducepatch command

Hi,

For a given W (n,3), where W contains the x,y,z coordinates of n-nodes.

tri=delaunay(W(:,1),W(:,2));  
G = trisurf(tri,W(:,1),W(:,2),W(:,3));     % to convert x,y,z into patch.

I used patch G, where

    FaceColor: 'flat'
    FaceAlpha: 1
    EdgeColor: [0 0 0]
    LineStyle: '-'
        Faces: [380x3 double]
     Vertices: [200x3 double],

and the command is :

reducepatch(G,0.8)

I got a problem with the reducepatch command

 "Warning: Error creating or updating Patch Error in value of property
 FaceVertexCData... Number of colors must equal number of vertices or faces".

Any idea? how to solve it? .... many thanks.

[Walter Roberson]

That sounds like a bug.

I would look for the possibility that the data you are passing in contains NaN or Inf, and I would also look for the possibility that you are reducing to so few faces that the computation is degenerate.

[Basheer Alwaely]

I used patch G, where

    FaceColor: 'flat'

    FaceAlpha: 1

    EdgeColor: [0 0 0]

    LineStyle: '-'

        Faces: [380x3 double]

     Vertices: [200x3 double],

and the command is :

reducepatch(G,0.8)

[Guillaume]

Can you provide your W array, so we can investigate?

[Basheer Alwaely]

Sure, I uploaded it above.

Cheers

Answer 1

[Guillaume]

I don't use patches enough to know if the problem is with reducepatch or with patch in general.

The error occurs after reducepatch has calculated the reduced vertices and faces (that bit works fine), when it tries to actually update the patches faces and vertices. It uses

set(yourpatch, 'Faces', newcalculatedfaces, 'Vertices', newcalculatedvertices);

This fails when the patch already has a FaceVertexCData property that is a vector or matrix corresponding to the old face/vertices colours as in your case, because that also needs to be updated to match the new number of faces/vertices.

You have several workarounds:

• make all the faces one colour before calling reducepatch:

G.FaceColor = 'r';  %for example
reducepatch(G, 0.8);

• don't modify the existing patch with reducepatch but create a new one:

[newFaces, newVertices] = reducepatch(G, 0.8);
newG = patch('Faces', newFaces, 'Vertices', newVertices);

Either way you're losing the colours of the original patch and I'm not sure how you'd go about recreating them.

It's probably worthy of a bug report as the reducepatch doc certainly says nothing about this problem.

edit: I have filed a bug report

[Basheer Alwaely]

My problem has been solved, Many thanks Guillaume