OBD:PLEA

ONI BINARY DATA OTLF << Other file types >> PNTA PLEA : Plane Equation Array switch to XML:PLEA page Overview @ Oni Stuff

---

Hex Translation Meaning 01 41 02 00 577 00577-.PLEA 01 00 00 06 3 level 3 AD DE dead not used F2 34 00 00 13554 13554 packages follow (first package outlined in black) First package (i.e., plane equation) follows 00 00 00 00 0.000000 first coefficient of the plane equation 00 00 00 00 0.000000 second coefficient of the plane equation 00 00 80 3F 1.000000 third coefficient of the plane equation 00 00 19 44 612.000000 fourth coefficient of the plane equation

Plane equation

The canonical equation for a plane in 3D is :

a * x + b * y + c * z + d = 0

where (a, b, c, d) are 4 real numbers. The plane is the set of points (x, y, z) verifying that equation.

It is likely that the four floats in one of a PLEA's packages are exactly the (a, b, c, d) of the above definition.

In that case, the first package of the above example defines the plane (0 * x + 0 * y + 1 * z + 612 = 0), i.e., the vertical plane z = -612.

It is possible, however, that the definition used is different, e.g. : a * x + b * y + c * z = d .

In that case, the first package of the above example defines the plane (0 * x + 0 * y + 1 * z = 612), i.e., the vertical plane z = 612.

Front/back

The 4 numbers (a, b, c, d) can also serve to define whether a 3D point (x, y, z) is on the "front" side of the plane or in the "back".

"points are in front of the plane if a * x + b * y + c * z >= d" (from commented Myth source)

That would mean the plane equation is a * x + b * y + c * z = d , not a * x + b * y + c * z + d = 0 .

It's rather easy to check (just flip the "normal" of the plane equation for a known axis-aligned quad).

The oriented "plane inequation" can be used for: culling; collision.

---

ONI BINARY DATA
OTLF << Other file types >> PNTA
PLEA : Plane Equation Array
Level file