OBD:PLEA: Difference between revisions

Revision as of 17:16, 29 May 2008

PLEA : Plane Equation Array

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Overview @ Oni Stuff

Offset	Type	Raw Hex	Value	Description
0x00	res_id	01 41 02 00	577	00577-.PLEA
0x04	lev_id	01 00 00 06	3	level 3
0x08	char[20]	AD DE	dead	unused
0x1C	int32	03 00 00 00	13554	array size
First element (black outline)
0x00	float	00 00 00 00	0.000000	'a' coefficient of the plane equation (x component of plane's normal)
0x04	float	00 00 00 00	0.000000	'b' coefficient of the plane equation (y component of plane's normal)
0x08	float	00 00 80 3F	1.000000	'c' coefficient of the plane equation (z component of plane's normal)
0x0C	float	00 00 19 44	612.000000	'd' 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.

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.

Planes are used for environment culling, collision detection and BSP.

@@ Line 25: / Line 25: @@
 :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.
-Planes are used for environment culling and collision detection.
+Planes are used for environment culling, collision detection and [[wikipedia:Binary_space_partitioning|BSP]].
 {{OBD_File_Footer | type=PLEA | prev=OTLF | next=PNTA | name=Plane Equation Array | family=Level}}