posted 04-28- 11:31 AM               

How does smooth shading work? From my (small) understanding, doesn't it use some math calculation to vary the light intensity over the surfaces of multiple polygons so as to make the surface look smooth?

And I have also heard that objects that are to be smooth shasded must have ploys that physicaly share their vertecies. For example, if you have a wheel LOD let's say, each adjecent poly of the wheel needs to share its neighboring ploy's verts. If you hve two verts that share the identical coords but are not shared as one vert, the smooth shading will fail, right? I have seem this happen, then I optimize (share) verts and it is fixed!

Is the math of the smooth shading done by the 3d engine? Or is it mapped to the polys like textures? When you click on "smooth shading" in AC3D, WHAT DOES THIS DO? Well I know it makes it look all somoth in the 3D window, BUT WHAT REALLY HAPPENED TO MY OBJECT?

Please, this is what I need to know!

Here is what I cam getting at: can you smooth shade over multiple LODS in SDOE? Can a wing made out of two pieces show a nice smooth shading across the entire wings with no shadow lines? TS said you can do this, and other panes look great, but all my planes suck and show seem lines between LODS

What can I do?

Much thanks for any help you can give me... any insight at all.. thanks!

posted 04-28- 12:00 PM               

What I do is merge the the lods together in AC3D ,snap the points, and then optimize vertices. I then cutaway one of the lods and export them. This will make the shading uniform over the 2 lods.

posted 04-28- 08:05 PM               

I will try that!

posted 04-28- 11:39 PM               

What SDOE uses is called Vertex lighting (lighting and shading are somewhat interchangable), or also gouroud(sp?) shading. Basically, you have a light source pointed in a particular direction, normally defined by a Normal. Also each vertice of the Mesh has a normal, termed a vertex normal to differentiate it from the face normal. (In simple flat shading systems the Face normal is used to light the whole poly with the one intensity. In SDOE it is used more for backface removal and other stuff)

When the lighting pass is done, intensity of the lighting for that particular vertice is assigned based on the relative orientation of the vertex normal and the light source normal. i.e. when the light source and vertex normal are pointing at each other then the intensity is highest, and when they point perpendicular to each other the light intensity if the smallest. Pointing away from each other will produce the sammest value of intensisty as well.

Once all of the vertices have a intensity value assigned, and the rendering of the polygon begins, the intensity of two vertices that make up an edge is interoperlated between each other, and then when each scan line of the polygon is drawn, the intensities along the edges are interoperlated with the corresponding point on the other edge.

It is not nessacery for two co-located vertices to be joined to produce smooth shading, so long as there vert normal point in exactly the same direction. Welding and such may be required for the shading routine of AC3D or MAX to work it out. IMO you can smooth in MAX without welding but the MAX2OBJ plugin upsets the vert normals.

What happens when you click smooth shading in AC3D is that the lighting type may be changed from face lighting, to vertiex lighting. Face lighting gives that faceted look.

posted 04-29- 12:07 AM               

But where and how is a vertex normal stored in the LOD? I know I can see and flip face normals in AC3D, but do you have any idea about vertex normals?

So to make a smooth shaded sphere, all vertex normals must face out perpindicular to the sphere surface?

Face normals are alway perp. to the surface, right? What are vert. normals perp. to? Can a vert. normal point in any direction?

This is a great help, much thanks! I feel I am getting close to knowing the secret

posted 04-29- 04:53 AM               

Here is a line describing a point in a LOD:
-4.921259880 -10.17099762 0.8044519424 0.0000000000 -1.000000000 0.0000000000 1.000000000 1.000000000

posted 04-29- 08:47 AM               

That clears up more again, how little I know!

So the last question is, how do these vert normals get set in AC3D? Can they be? Or do they fall out from the surface normals?

posted 04-29- 09:08 AM               

First explode the wing with a 0 distance.

1.Merge only the polygons of top part then optimize vertex for this object.
2.Merge only the polygons of the bottom part then optimize vertex for this object.
3.Merge the 2 objects but do not optimize vertex then export.

You have to determine which polygons in front of the wing goes with the top part so that the wing looks correct.

Sv,

posted 04-29- 07:20 PM               

In simple terms, to apply smooth shading to an edge (which is the join between two polygons) you have a vertex which bisects the angle between the two faces. and to make a sharp edge the normals are perpendicular to the faces that make up the edge.

Sharp Edges

Smooth shaded edges (and point)

Of course you never see this, the 3D package does it for you based on other types of input.

posted 04-29- 07:53 PM               

So this is my understanding:

When you smooth shade and object in AC3D, the vertex normals are adjusted to accomplish this. When the LOD is exported via Hippie's plug-in, the vert normals reflect this change.

This is why the AC3D instructions mposis gave me should work:

1. You have the entire right wing as an object. Now you optimize verts, now the verts are shared.

2. Now you SMOOTH SHADE. This step alters the vert normals to shade the object corrrectly

3. Now you cut away the wing tip object. Now you have two objects.

4. Now you export each object as a LOD. They will retain the smooth shading they were assigned when it was one object before, EXACTLY like texture mapping.

Is this right? Is it just like texture mapping then? I can map one big object, now when I split into many LODS, the texture map still works. The key step is the moment I map the texture. Now it is mapped and the mapping travel with the polys (more exact is verts?) So is the key moment for shading when I click the "Smooth shade"?

Much thanks guys, this is SO helpful. If I understand this correctly my planes will be 10 times better, but MAN do I have work to do

posted 04-29- 09:06 PM               

Yes, if you texture map a big object and cut away polygons from it the texture coordinates does not change on the polygon.
The only time they will change is when you do a remap texture coordinates.

The coordinates, vertex normals, and texture coordinates of the polygons do not change when you cut it from an object.

posted 05-09- 07:20 AM               

I think this may be the case, I wish I could see vert normals in AC3D!

So sall I try to take the wing apart again, then optimize the top and bottom seperately, then merge, and then export with no vert optimization? Maybe I will try this...

posted 05-09- 09:50 AM               

I think though Bryan, you have explained to me why the model of the PBY does what it does as far as shading goes. So let me add my thanks to sv's.

posted 05-09- 04:48 PM               

1. select the exact vertices of the faulty surface
   
2. "surface/cut-away object"
   
3. on the new object flip the normals twice. DON'T ASK ME WHY!!!
   
4. optimize vertices on the new object
   
5. smooth
   
6. merge with previous parent object. DON'T optimize vertices anymore!
   
7. figure out why the f**k the texture mapping was lost in the process