What’s a normal in 3DC

I’m obviously new to 3d modelling as I haven’t thought of this before. andnbsp;What happens if the quads are not coplanar? andnbsp;I see 3DC handles it but not sure I understand the significance. andnbsp;Is there a limit to how non-coplanar they can be and retain sensible rendering? andnbsp;

George

Howdy,

I’m writing a script to do a fractal terrain (which nearly works) based on the make a face script that comes with 3DC.

I’m wondering what andnbsp;a normal is in 3DC. andnbsp;Since I’ve defined the corners of my plane, the normal is, well, normal. andnbsp;

In the script I use the addpointandnormal method using a dummy normal. andnbsp;But I use the same one for all faces, none of which face the same way, and things look ok. andnbsp;Does it define the top and bottom of a face? andnbsp;Evidently the vector doesn’t have to be a correct normal for the thing to work.

Thanks for any help. andnbsp;And if anyone’s interested I’ll post the script in the Scripting forum when it works ok.

George

Thanks Alex.

I guess I didn’t REALLY answer the question did I? :-[

Richard

A normal is a vector, used to calculate the way your surfaces will look like. A simple representation of a normal is an arrow sticking out at 90 degrees from the middle of a surface. It helps the renderer to find out which way surfaces point, whether they are visible or not. More sophisticated renderers, like we have nowadays, use ‘vertex’ nomals. Those are situated not in the middle of a face, but at each vertex or point delimiting this face. Each face has multiple normals, each situated at a vertex (point) delimiting the face. The normal at a given vertex is calculated as a sort of average of the normals of the faces that share this vertex, and allows a much more sophisticated rendering of curved surfaces, by interpolating the values of the ‘vertex’ normals to render the pixels within the surface, and not the whole surface as a flat entity. So a flat surface can become a curved one if the ‘vertex’ normals point in slightly different angles…

Alex

Normals are used for shading. Changing the normals is what the Crease operation does to change smooth sections into creases (and the reverse).

You needn’t get these right since you can just generate the normals using the andquot;GenerateNormalsandquot; method.

Richard

Howdy

Thanks for the info on your normals. andnbsp;I need to digest Alex’s reply in relation to whether the surface is best generated in triangles or quads. andnbsp;I’ll certainly stick with quads at the moment. andnbsp;When I understand what I’m talking about I may need to deepen the question…

The script will be a little while, but definitely coming. andnbsp;I stupidly wrote it (and spent xx time debugging) on the briefest description of what to do. andnbsp;Only then I searched for code to steal, and there is, of course, plenty. andnbsp;So I will use a more efficient algorithm. andnbsp;Also now have ideas to best incorporate it. andnbsp;Watch this space andnbsp;

George

I would definitely use quads. Quads are better for modelling and 3DC likes them better than triangles (the Smooth operation definetely likes them better).

If people want triangles then can always triangulate the object afterwards and a re-crease.

Richard

George,

BTW I am absolutely certain that people will be interested in your script. And I am quite interested to see it myself.

Richard

They really ought to be planar, but what you are doing pretty much guarantees that they won’t be. They render pretty well even if significantly non-planar.

What happens is that 3DC triangulates them internally and renders (Direct3D can’t directly render non-triangles). Usually this looks just fine. Dont’ worry about it unless you are going to have large quads.

Richard