How different geometries work in Odeon (and is it possible to calculate volume).

A. You can add a surface in ODEON using vertices from neighbour surfaces.

To do so enter the modelling options in the 3D view:

Press F1 to obtain the ODEON help. Follow the instructions under the heading "Defining a surface from existing points using the 3D View, the Windows Clipboard and the ODEON Edit".

A: ODEON is capable of working with pretty large and complex rooms up to 2 kilometers in each dimension and a large number of surfaces. The only limit in the number of surfaces is imposed by the amount of RAM and the power of the PC, since ODEON itself does not impose any other limit. From our experience so far rooms with up to 100000 surfaces can be manageable, although some navigation functions may be slowed down.

A: You should use exterior type for a surface that normally belongs to the interior of a room but you want to use it as exterior, i.e. providing less scattering at lower frequencies. When a room is loaded into ODEON, the surfcases are automatically distinguished between exterior and interior ones, according to the Interior margin setting in the Room Setup. By default, the interior margin is 10 cm from the boundary surfaces in the room. This means that surfaces falling inside the interior margin are considered as boundary surfaces, displayed in black, while surfaces deeper inside the room and away from the interior margin are considered interior surfaces. These are displayed by a greenish color. An interior surface provides quite high scatering throughout the whole frequency range, while an exterior surface is expected to provide less scattering at low frequencies.

You can force a surface to be exterior, even though it was detected as interior, if you believe that due to its shape the scattering is less at low frequencies.

A: In ODEON any surface is represented in a healthy way by a closed loop of points. Subsequently, each point is defined by the 3D coordinates: x, y, z, as you can see in any room file opened in the ODEON editor.
When a window is placed in the middle of a wall or when simply there is a hole in a surface, ODEON has to create one loop of points both along the boundary of the wall and the boundary of the hole. An extra line appears in the wall inside ODEON giving the indication that the points defining the hole are connected to the points defining the boundary in the same loop. So, this line is an indication of a healthy imported surface with a hole inside.
You can see the loop of points for any surface very easily within from the 3DView, by pressing the N key.

Q: Can I combine two models from the Odeon extrusion modeller?

A: Yes below video describes how you can combine two extrusions from two different extrusion planes: a plane section and a cross section. Note that when you have combined the two models you cannot go back to the extrusion modeller and draw in the combined model, you must use the Odeon Editor.

A: There are basically four ways to create a room models: import from dxf-files/3ds-files, by using Google SketchUp and SU2Odeon, extrusion modelling or parametric modelling in a text editor. Read More.

Below several ways to handle 3D models for use in ODEON are illustrated:

Q: Open GL shows a hole where there is a surface?

A: The problem could be that the lines cross ower creating a butterfly surface, like the surface shown below (100 101 102 103)

Q: How is the surface normal and insertion point of surfaces calculated?

A: Precise surface equations for each surface in a room model are essential for all computations in a program such as Odeon. The surface equation Ax + By + Cz + D = 0 of a surface plane is based on an insertion point as well as a surface normal.

If all corners of each surface would be exactly in one plane and there were no limits to numerical precision of computers, there would not be a problem. Neither is the case, so in Odeon these equations are fitted from all points on the perimeter of the surface weighting their contribution relative to the area of the surface which the two closest edges describe – that is, very close neighboring points has little weight whereas distant neighboring points carry height weight. Consequently Odeon can handle surfaces with perimeter points that derivates quite a bit from the perfect plane. In early versions of Odeon such error would often lead a substantial loss of rays or plane equations which described the geometry poorly – the geometry had to be corrected over and over again.

Note that Odeon doesn’t mind which order the perimeter points of a surface is given (clockwise or counterclockwise) both sides of the surface is automatically described in one go.

Also note that Odeon allows concave surfaces, surfaces with shapes such as U,O,L,H are allowed to be described by just one surface (sequence of points), no need for surface subdivision.

Although these are features are hidden, it does mean that modeling is made much easier by Odeon.