Nurbs - UV Map

What is a Nurbs Surface and
how it can help you to create an OPT model.

For me a Nurbs Surface it's a Wallpaper. No more, no left and I use Nurbs Surface on 3D computer model exactly like I can use wallpaper in the real life to turn a simple brown box into a more interesting box with colours. If the wallpaper are to large, I can trim it to fit the side of the box.
The Nurbs Surface speed up you OPT creation. Why ? When you create a Nurbs surface you not only do one simple thing at the same time.

1^st You create the base of small group of polygon.
2^nd Assign UV Coordinate to your future small group of polygon.

How Rhinoceros 3D assign texture 26.10.2006 19:30create a planar surface in Rhino the UV Coordinate as been automatically assign to this surface.

Sometimes Rhino place the UV coordinates upside down or rotated 90° or -90°. To change this you need to edit the surface by reversing U, reversing V direction or swapping UV.

If your surface are square you need to use a square Texture on it. If you have a rectangular surface and you apply a Square texture on it or your texture will appear very deformed.

The same texture for square, rectangular and stretched Nurbs Surface.

Now when you have this information you need to choose the right shape for your texture. Square or rectangular to have a very minimal or no texture deformation on them. If you need to have a trapeze shape of surface you must start with a square or rectangular surface and trim all unwanted section.

If you have a closed loft surface (like my asteroid) in your project you can texture it with a square texture. For Rhino, the Sphere and closed Loft Surface as been textured with the same method.

Don't worry if you have 1200 polygons in your polygon mesh, you can divide this polygon mesh in several part with Lithunwarp or Ultimate Unwarp 3D.

UV Mapping is Upside down or Rotated ?

When you create a surface with Rhino sometime the UV Coordinates are not aligned in the direction you want. In Rhino the surface UV direction it's and texture UV mapping it's the same. So if you reverse/swap U or/and V direction you will modify the texture coordinate.
How you can modify this : Go to Analyse Menu and click on Direction. Select the surface you want and Reverse V, Reverse U, Swap UV to align your texture. You can also Flip surface normal if needed.

You want to create a small cube fully textured with this texture.

After you have exploded your cube and applied texture on each face you have this.

Now you can modify surface UV direction to orient the same texture in the direction you want.

Puzzle texturing method

It's also possible to re-use the same texture 4 times to texture one face.
You just need to split the surface in 4 parts or create 4 different surfaces.

Apply texture on complex pipe

You need to create a very complex pipe for one of your model but you have stop your project because the shape are to complex to texture in Ace DXF or OPTech ?

This is a basic texture created with the MS Paint.
Now imagine what possible effects you can have with a good paint program.

Result in Nurbs.

Result in Polygon mesh.

As you can see the UV mapping is not very relax on some section of the pipe. If you need one pipe for your project make sure to not make your pipe along a short radius drive curve.

Trimmed Nurbs Surface

Rhino use each corner of a planar surface to apply texture. Upper right-left corner and lower right-left corner. Now if you use a trimmed planar surface Rhino will not move the UV Coordinate to the new corner. When you have asked Rhino to create surface from Planar curve the program take the overall size of it, create a square or rectangular Nurbs Surface, then Rhino remove everything outside of your curve. But Rhino keep all UV Coordinate of the surface he created during the process.

Texture used to render the STOP

The Stop. Planar UV Mapped Nurbs surface. Pay attention to the Isoparametric line splitting the STOP in four parts.

The Stop Planar UV Mapped surface with Coordinate Texture. Pay attention to the Isoparametric line. In vertical from Number 8 to 278. In horizontal from number 136 to 150.

Split planar surface by isoparametric line.

In Rhino it's possible to split one surface by the isoparametric line. Now see the four new Nurbs surface, they have their own texture coordinate.

One of the texture for the STOP.

The STOP with 4 deferent texture.

The Stop Planar UV Mapped split surface. Pay attention to the Isoparametric line splitting the STOP in 16 parts.

As you can see you can texture one object just like a puzzle. This can be very useful because in X-Wing Alliance the maximum size for each texture are 256X256 pixels. So now instead of using one unsupported 512X512 texture you can have the same look if you split your large texture into four 256X256 texture. This technique can be used for large ship like SSD, ISD, VSD, etc or for surface were you need a large amount of detail. You are not limited to split a square surface you can split a rectangular surface. Also if you need you can rebuilt the surface to change the number of isoparametric line. And if splitting by isoparametric line you can split surface with construction element like line or other surface.

Last modification on 10.07.2004 14:26
by Guillaume Saumure.