Modern Math TransformPoint

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TransformPoint

Applies a matrix to a point, translation included.

Syntax

TransformPoint( byref a as Mat4, byref v as Vec3 ) as Vec3

Notes

• A point has a position, so the translation column applies -- this is the w=1 case.
• TransformVector is the w=0 case for directions, and using the wrong one is the classic bug that translates a surface normal.
• It divides by w afterwards, so a projection matrix works.

Examples

#import "std/numeric"
using numeric

dim as Mat4 m
for i as int32 = 0 to 15
    m.m( i ) = 0
next
for i as int32 = 0 to 3
    m.m( i * 4 + i ) = 1
next
m.m( 12 ) = 10               '' the translation column

dim as Vec3 p = type<Vec3>( 1, 2, 3 )
dim as Vec3 r = TransformPoint( m, p )
print r.x                    '' 11 -- translated

'' A DIRECTION must not be translated -- that is TransformVector
dim as Vec3 d = TransformVector( m, p )
print d.x                    '' 1

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