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Are there Surface "Normals" on Meshes supported?


Xaver Roelofs
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Are there Surface "Normals" on Meshes supported?

On some of my Meshes i created, i used more than one Materials (Faces). And there are uggly seams on the changeover of the Materials. With a good align of the Normals the seams will disappear.

 

At the moment i ve no good normals aligned Mesh to test.. as it is a huge work to align a Mesh. So my question above.. thx for answers.

 

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The uploader inteface is misleading here. The Generate normals spinner is not active until you change the angle. As long as you don't touch it, it will do nothing and the normals will be as specified in your Collada file. The UI problem is that there is no indication of whether it is active or not. (I made a jira asking for this simple UI error to be corrected, but it was closed without action.)

You can use the generate normals to smooth edges globally according to the angles between the meeting faces by using the generate normals spinner. However, most 3D programs will give you much better control than that (at least Blender does), and if you use that, you don't want the uploader to override the Collada normals. In that case you need to leave the Generate normals spinner alone.

You didn't say what program you are using, but if it was Blender, you can control sharp/smooth edges by Mesh:Faces:Set smooth/solid (solid=sharp), or. more precisely, by using the edge-split modifier. That works either by using a limit angle, like the uploader, or on edges explicitly marked as sharp, or both. The angle-based process in Blender is superior tyo the uploader one because it works across UV seams and material joins, while the uploader one does not.

You should be aware that sharp edges require more data and so increase the download weight component of prim equivalence.

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Good news.. and very importend to know that the normal-option is deactiveted if it is untouched.

 

I am using "3ds Max 2011" and there is a simple Normals-Modifier where i can adjust each normal.. this is a hard work to do so. I am not conversant with Blender, so may there is a better 3rd-party Modifier out i've looking for.

 

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I normally set the spinner to the same normal angle I have set within the 3D editing program, which is never 75. Are you saying that if you didn't set the normals in your program that you can set them via the spinner? I haven't seen that work on the simple cylinder test I was doing back when I was working on my pipeline, is that something that has changed or the smooth it provides is not smooth at all :)

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Yes, you can set your normals with the spinner. Like Drongle said, once you change the number, normals will be applied.

I personally have used the Importer normals only once, at my first mesh upload in october. For me it is pretty much useless, because it kills all hard/sharp marked edges, too, If you use high angles. So I always set the normals in Blender and never touch the spinner in the Importer.

But I dunno if it has changed, cause I haven't used it for so long now.:matte-motes-nerdy:

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I haven't used it in a long time, as it is rather limited. It certainly used to work smoothing sharp edges according to angle, but only if the edges were not UV seems. So it depends on your UV map. If you have set sharp/smooth in you 3D program, and you exporter exports them accurately, then you should not touch it, because if you do it will override the normals from the Collada file. Some of this may have changed since I last investigated it. Time for some new experiments, maybe.

Whoops, I hadn't read Arton's reply .... he already said all that.

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I don't understand why you are setting the normals manually. There is generally a recalc normals item that faces all the normals to one side of a surface. There is also a feature to reverse normals to the other side of a surface. So, ...

I cannot imagine a situation were some faces of a surface face one side and other faces the other, like a window in a wall. I think that would confuse most systems.

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in 3ds Max, when you have Polygon subobject level selected in the Command Panel > Modify tab, you can set smoothing groups.  Any group with adjacent polygons will have a single vertex normal when smoothed.  Adjacent polygons with different smoothing groups will have more than one normal, so will render as a hard edge when lighted in SL.

Since SL mesh objects are rendered as one-sided, you need to make sure the normals point "outwards" towards the side the camera will see it from.  If the object will be seen from two sides, then you need to double the geometry and flip the normals on one of the sets.

Flip triangles and unify normals are useful for getting them all pointing in the general direction you want. 

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The cool thing about normals in this case is that you can define for each face, how it shall behave regarding ligthing. For sculpted prims we had this ugly problem that whenever we wanted to define a sharp edge, we needed either to collapse 2 rows/columns of vertices, or bake the sharp line into the texture (or both).

With meshes you can have one of 2 different lighting behaviours defined on each (model-) face:

 

  1. either you have the "smooth lighting" behaviour (like with sculpties)
  2. or you have the "flat lighting" behaviour (which generates the same light response on the entire face).

In Blender you find the smooth/flat setting for an object (or for the selected faces when in edito mode). In most cases the diffenrent lighting behaviour on an object is directly dependent on the amount of bending on the surface and it can be "guessed" from the angles of adjacent faces.

So i think, that the normal generator is good for those situations where you have forgotten t define the normals but know that the generation will work for you as a nice shortcut for testing.

But mostly you better define your normals by yourself ;-)

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