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OpenGL GL_SMOOTH - Not so smooth ?

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Hi, I'm creating a small soft with OpenGL but when I load a 3DS model it looks like faceted ! There is no smoothing between the faces. I use Gl.glShadeModel(Gl.GL_SMOOTH); but it change nothing ! Here is a picture : http://picasaweb.google.com/viewon01/OpenGL#5380203925050881714 Here, you can download the Smurf model : http://www.3dvalley.com/3d-models/characters Do you have an idea ? Here is the way I create the normals : Vector3[] sum = new Vector3[Vertexes.Count]; for (int jj = 0; jj < TrianglesIndices.Count / 3; jj++) { int indice1 = TrianglesIndices[jj * 3]; int indice2 = TrianglesIndices[jj * 3 + 1]; int indice3 = TrianglesIndices[jj * 3 + 2]; Vector3 v1 = Vertexes[indice1]; Vector3 v2 = Vertexes[indice2]; Vector3 v3 = Vertexes[indice3]; // Calculate the surface normal Vector3 e1 = Vertexes[indice1] - Vertexes[indice2]; Vector3 e2 = Vertexes[indice2] - Vertexes[indice3]; Vector3 surfaceNormal = e1.Cross(e2); // Sum it at the vertex index sum[indice1] += surfaceNormal; sum[indice2] += surfaceNormal; sum[indice3] += surfaceNormal; } for (int index = 0; index < Vertexes.Count; index++) { sum[index].Normalize(); Normals.Add(sum[index]); }

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Thanks,

I don't understand, I have a per-vertex normal.

I calculate the surface normal for each vertex, BUT I sum it...

at the end I normalize it, so every normal is different. Right ?

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Quote:
Original post by maspeir
Vertex normals are averaged, not just summed.

He normalizes them at the end, which ensures the normals are of unit length. It doesn't matter whether you sum them or average them, you must normalize them in the end. Averaging alone is not good enough, because it doesn't ensure the normals are of unit length.

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I understand the need to normalize them after averaging. This is the first time I've heard that they can be summed with the same effect. I stand corrected.

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Thanks for your answers,

Can you tell me where I'm assigning normals to incorrect vertices ?

I don't understand where I have do an error !

Thanks

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One idea: your vertices aren't shared, I mean, all triangles have 3 vertices, which are not shared with the other, neighboring triangles, although they seem to be the same verices.
How many polygons/vertices you have?
If vertices=3*polygons, your vertices aren't shared, so you cannot calculate average that way.

I hope it made sense, or I didn't misunderstand something, or not giving dumb advice.

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Thanks,

It is an idea, in fact I read a 3DS file... so I have supposed they are correctly organized !

But maybe you're right !
I have :
- 32168 vertices !
- 21440 triangle (with 3 indices for each)

So, how can I reorganize my vertices... it sounds a complex task to keep good performance!

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I worked with .3ds too,
If there's texture mapping in 3dsMax, some triangles vertexes will brake in 3dsMax exports, because I think they are optimized for VBO or the old vertex buffer or something, where you have to index normal/vertex/texture coordinates in the same way, and texturing may brake triangles (the same vertex can have different texture coordinates on the different triangles). You wont recognize these braked vertexes in the 3dsMax itself.
By looking at your model, it seems a typical case, when the mesh has more polygons than vertices. (if they are shared)

If you create a 'geosphere' in 3dsMax, by default, it will have 320 polys, and 162 verts. (So more polygons!)
But you have a lot more vertices, than polygons.
So I guess I'm right.

I don't know how to overcome this, I think max has some logic in the indexing, but to puzzle it out how, pfff that's really hard.

I suggest you simply consider vertexes to be same, if their all coordinates are the same. (I think they should be precisely equal)

So find these somehow, than find the triangles they are on, find out the smoothing group ID of that triangle, than average those normals.

You don't have to do it realtime, calculate them at the beginning.

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Quote:
Original post by viewon01
So, how can I reorganize my vertices... it sounds a complex task to keep good performance!


It is the job of the artist and not the programmer. How do you know that the faceting wasn't intentional?

Quote:
If there's texture mapping in 3dsMax, some triangles vertexes will brake in 3dsMax exports, because I think they are optimized for VBO or the old vertex buffer or something,


The actual reason is that the 3ds max SDK is ass-backward when it comes to vertex normals. As the developer of an exporter you have 2 choices.

1) Fart around with some very ropey data stored in multiple formats in multiple locations, then cross reference all of that with the relevant smoothing groups.
2) Sod it off and just write out data without shared normals.

I'll let you guess which path they chose....

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