Modern Math Cross

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Cross

Returns a Vec3 perpendicular to both inputs; swapping them flips its direction.

Syntax

Cross( byref a as Vec3, byref b as Vec3 ) as Vec3

Notes

• Vec3 only -- the cross product is not defined in 2 or 4 dimensions.
• Not commutative: Cross( a, b ) is the negation of Cross( b, a ), and getting the order wrong flips a surface normal.
• Its length is the area of the parallelogram the two vectors span, so it is zero for parallel inputs.

Examples

#import "std/numeric"
using numeric

dim as Vec3 a = type<Vec3>( 1, 2, 3 ), b = type<Vec3>( 4, 5, 6 )

dim as Vec3 c = Cross( a, b )
print c.x & " " & c.y & " " & c.z             '' -3 6 -3

'' Perpendicular to both, by construction
print Dot( c, a )            '' 0
print Dot( c, b )            '' 0

'' NOT commutative -- the order flips the normal
dim as Vec3 d = Cross( b, a )
print d.x                    '' 3

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Library: Math Library
Category: Math Library
Documented under: Members