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FrustumTest< T > Class Template Reference

#include <ImathFrustumTest.h>

Public Member Functions

Constructors
 FrustumTest () IMATH_NOEXCEPT
 Initialize camera matrix to identity. More...
 
 FrustumTest (const Frustum< T > &frustum, const Matrix44< T > &cameraMat) IMATH_NOEXCEPT
 Initialize to a given frustum and camera matrix. More...
 
Set Value
void setFrustum (const Frustum< T > &frustum, const Matrix44< T > &cameraMat) IMATH_NOEXCEPT
 
Query
bool isVisible (const Sphere3< T > &sphere) const IMATH_NOEXCEPT
 
bool isVisible (const Box< Vec3< T >> &box) const IMATH_NOEXCEPT
 
bool isVisible (const Vec3< T > &vec) const IMATH_NOEXCEPT
 Return true if the point is inside the frustum. More...
 
bool completelyContains (const Sphere3< T > &sphere) const IMATH_NOEXCEPT
 
bool completelyContains (const Box< Vec3< T >> &box) const IMATH_NOEXCEPT
 
IMATH_INTERNAL_NAMESPACE::Matrix44
< T > 		cameraMat () const IMATH_NOEXCEPT
 Return the camera matrix (primarily for debugging) More...
 
IMATH_INTERNAL_NAMESPACE::Frustum
< T > 		currentFrustum () const IMATH_NOEXCEPT
 Return the viewing frustum (primarily for debugging) More...
 

Detailed Description

template<class T>
class FrustumTest< T >

template class FrustumTest<T>

This is a helper class, designed to accelerate the case where many tests are made against the same frustum. That's a really common case.

The acceleration is achieved by pre-computing the planes of the frustum, along with the ablsolute values of the plane normals.

How to use this

Given that you already have: Imath::Frustum myFrustum Imath::Matrix44 myCameraWorldMatrix

First, make a frustum test object: FrustumTest myFrustumTest(myFrustum, myCameraWorldMatrix)

Whenever the camera or frustum changes, call: myFrustumTest.setFrustum(myFrustum, myCameraWorldMatrix)

For each object you want to test for visibility, call: myFrustumTest.isVisible(myBox) myFrustumTest.isVisible(mySphere) myFrustumTest.isVisible(myVec3) myFrustumTest.completelyContains(myBox) myFrustumTest.completelyContains(mySphere)

Explanation of how it works

We store six world-space Frustum planes (nx, ny, nz, offset)

Points: To test a Vec3 for visibility, test it against each plane using the normal (v dot n - offset) method. (the result is exact)

BBoxes: To test an axis-aligned bbox, test the center against each plane using the normal (v dot n - offset) method, but offset by the box extents dot the abs of the plane normal. (the result is NOT exact, but will not return false-negatives.)

Spheres: To test a sphere, test the center against each plane using the normal (v dot n - offset) method, but offset by the sphere's radius. (the result is NOT exact, but will not return false-negatives.)

SPECIAL NOTE: "Where are the dot products?" Actual dot products are currently slow for most SIMD architectures. In order to keep this code optimization-ready, the dot products are all performed using vector adds and multipies.

In order to do this, the plane equations are stored in "transpose" form, with the X components grouped into an X vector, etc.

Definition at line 85 of file ImathFrustumTest.h.

Constructor & Destructor Documentation

template<class T >
FrustumTest< T >::FrustumTest ( )
inline

Initialize camera matrix to identity.

Definition at line 92 of file ImathFrustumTest.h.

template<class T >
FrustumTest< T >::FrustumTest ( const Frustum< T > &  frustum,
const Matrix44< T > &  cameraMat 
)
inline

Initialize to a given frustum and camera matrix.

Definition at line 101 of file ImathFrustumTest.h.

Member Function Documentation

template<class T >
IMATH_INTERNAL_NAMESPACE::Matrix44<T> FrustumTest< T >::cameraMat ( ) const
inline

Return the camera matrix (primarily for debugging)

Definition at line 141 of file ImathFrustumTest.h.

template<typename T >
bool FrustumTest< T >::completelyContains ( const Sphere3< T > &  sphere) const

Return true if every part of the sphere is inside the frustum. The result MAY return close false-negatives, but not false-positives.

Definition at line 239 of file ImathFrustumTest.h.

template<typename T >
bool FrustumTest< T >::completelyContains ( const Box< Vec3< T >> &  box) const

Return true if every part of the box is inside the frustum. The result MAY return close false-negatives, but not false-positives.

Definition at line 290 of file ImathFrustumTest.h.

template<class T >
IMATH_INTERNAL_NAMESPACE::Frustum<T> FrustumTest< T >::currentFrustum ( ) const
inline

Return the viewing frustum (primarily for debugging)

Definition at line 144 of file ImathFrustumTest.h.

template<typename T >
bool FrustumTest< T >::isVisible ( const Sphere3< T > &  sphere) const

Return true if any part of the sphere is inside the frustum. The result MAY return close false-positives, but not false-negatives.

Definition at line 216 of file ImathFrustumTest.h.

template<typename T >
bool FrustumTest< T >::isVisible ( const Box< Vec3< T >> &  box) const

Return true if any part of the box is inside the frustum. The result MAY return close false-positives, but not false-negatives.

Definition at line 262 of file ImathFrustumTest.h.

template<typename T >
bool FrustumTest< T >::isVisible ( const Vec3< T > &  vec) const

Return true if the point is inside the frustum.

Definition at line 318 of file ImathFrustumTest.h.

template<class T >
void FrustumTest< T >::setFrustum ( const Frustum< T > &  frustum,
const Matrix44< T > &  cameraMat 
)

Update the frustum test with a new frustum and matrix. This should usually be called just once per frame, or however often the camera moves.

Definition at line 175 of file ImathFrustumTest.h.

The documentation for this class was generated from the following file: