 |
Atoms Crowd
7.0.0
|
|
Atoms Crowd
7.0.0
|
#include <ImathFrustumTest.h>
Public Member Functions | |
Constructors | |
| FrustumTest () noexcept | |
| Initialize camera matrix to identity. | |
| FrustumTest (const Frustum< T > &frustum, const Matrix44< T > &cameraMat) noexcept | |
| Initialize to a given frustum and camera matrix. | |
Set Value | |
| void | setFrustum (const Frustum< T > &frustum, const Matrix44< T > &cameraMat) noexcept |
Query | |
| bool | isVisible (const Sphere3< T > &sphere) const noexcept |
| bool | isVisible (const Box< Vec3< T >> &box) const noexcept |
| bool | isVisible (const Vec3< T > &vec) const noexcept |
| Return true if the point is inside the frustum. | |
| bool | completelyContains (const Sphere3< T > &sphere) const noexcept |
| bool | completelyContains (const Box< Vec3< T >> &box) const noexcept |
| ATOMSMATH_INTERNAL_NAMESPACE::Matrix44< T > | cameraMat () const noexcept |
| Return the camera matrix (primarily for debugging) | |
| ATOMSMATH_INTERNAL_NAMESPACE::Frustum< T > | currentFrustum () const noexcept |
| Return the viewing frustum (primarily for debugging) | |
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.
|
noexcept |
Return true if every part of the box is inside the frustum. The result MAY return close false-negatives, but not false-positives.
|
noexcept |
Return true if every part of the sphere is inside the frustum. The result MAY return close false-negatives, but not false-positives.
|
noexcept |
Return true if any part of the box is inside the frustum. The result MAY return close false-positives, but not false-negatives.
|
noexcept |
Return true if any part of the sphere is inside the frustum. The result MAY return close false-positives, but not false-negatives.
|
noexcept |
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.