Polygon type A and B

NOVA comes with two polygon types, Polygon A and Polygon B. This table shows the differences between both types:

  Polygon A Polygon B
Maximum number of points 10 20
Textures with transparency options ALL NONE
Skew and Raise options YES NO
Raise top points YES NO

POLYGON POSITION:

This shows the same 8-sided polygon in both positions.
There are two additional options when making an horizontal polygon and they work the same way as in the Cube.
  • Skew: You can skew the front and back sides of the polygon from right to left and/or vice versa.
  • Raise Polygon: Raises one end of the polygon.
This is an example of two polygons using the Skew option.
The same polygon but raised at the front.

 HORIZONTAL POLYGONS - IMPORTANT NOTES

When placing the polygon in a horizontal position the Y axis becomes in effect the height of the polygon.

The lower side of the polygon will stay on the ground so the altitude or Y axis coordinates will be 0 (zero).

In the lefthand picture if you place points 1 and 8 below ground level you will not see sides 1 and 7 that are partially in the scenery.

 

Another important issue will be visibility problems. On the left is an example.

This problem is easily resolved by reversing the side drawn in the texture panel. More information can be found here.

There is also a close relationship between the physical shape of the polygon and the textured points positions otherwise the polygon will be distorted somehow with rotated points or in complete disorder.

 

TRIANGULATION

This feature only applies for the base and top sides of the polygon, or the front and back sides if the polygon is drawn horizontally.

You will have to use this feature almost every time you have an asymmetric shape.

This is one of the many cases you may get. The lefthand picture represents a building with an L surface shape and on the right you'll see what happens if you don't use the triangulation option for polygons.
Triangulation is not another thing that just divides the surface into triangles in any way or order. You will have to enter, for each triangle, the points that make it up.

The triangulation panel will look something like this when accessed the first time.

To the left you have the polygon with the vertexes numbered from 1 to 9 then from A to K if you have up to 20 sides.

To the right you have all the required number of sets for as many triangles as you need. Each set must be filled with 3 numbers or points. So we will start, in any order, making the triangulation...as

126 for example...and so on. If your polygon has more than 9 sides then you will have to use letters as well such as 7DA or any other combination.

In the end your screen will look something like this.

Each triangle shows a different color, this color is the same color as the set box number.

You can enter the points in any order - 123, 321, 213 and 132 all mean the same.

 

 

Hopefully the polygon will display properly once the triangulation is done.
You can also use the polygon if you have a building where you have to repeat the same texture a few times, something like we have here.

Do you need to make a triangulation here? Well I should say it all depends on the quality of building texturing you want to have on the roof. The answer is yes and no...

If you don't use triangulation the program will generate the points in accordance with the entries you have made.

If you want to use the triangulation you now have some options:

You could just make 2 big triangles here, like 126 and 167, and it will work. The problem here is that the roof will be so stretched that it will be very ugly. Doing this would be almost the same as not using triangulation.

The best option would be to repeat the same texture in the roof. This is something hard to do the first time but it is worth trying.

This building looks like this without triangulation. What I really want is to use the same roof texture 4 times instead of only once. So texturing will be improved if this is what we are looking for. For this exercise I have numbered the points on the texture for better understanding.
This is graphically the right distribution of points to be made. If you fold this picture on the dotted lines you will see that some points overlap and share the same position.
If you fold the picture point 4 will be placed over point 2, 5 over 3, and 6 over 2.
The same will happen to the lower points and, in the end, you'll get just one picture that will look like this.
And, finally, we make the triangulation.
The final version of the building. You get some important advantages using this method -
  • Your textures can be smaller to cover the same surface so you'll use less space and gain CPU performance or better frame rate.
  • Avoid fuzzy buildings texturing. This is more obvious if your building is very long like a 300 meter terminal.

For more information you can load the file NOVAEX03.NOV used in this example.