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///////////////////////////////////////////////////////////////////////////
#ifndef INCLUDED_IMATHFRUSTUMTEST_H
#define INCLUDED_IMATHFRUSTUMTEST_H
//-------------------------------------------------------------------------
//
// This file contains algorithms applied to or in conjunction with
// Frustum visibility testing (Imath::Frustum).
//
// Methods for frustum-based rejection of primitives are contained here.
//
//-------------------------------------------------------------------------
#include "ImathFrustum.h"
#include "ImathBox.h"
#include "ImathSphere.h"
#include "ImathMatrix.h"
#include "ImathVec.h"
#include "ImathNamespace.h"
IMATH_INTERNAL_NAMESPACE_HEADER_ENTER
/////////////////////////////////////////////////////////////////
// FrustumTest
//
// 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.
//
template <class T>
class FrustumTest
{
public:
FrustumTest()
{
Frustum<T> frust;
Matrix44<T> cameraMat;
cameraMat.makeIdentity();
setFrustum(frust, cameraMat);
}
FrustumTest(const Frustum<T> &frustum, const Matrix44<T> &cameraMat)
{
setFrustum(frustum, cameraMat);
}
////////////////////////////////////////////////////////////////////
// setFrustum()
// This updates the frustum test with a new frustum and matrix.
// This should usually be called just once per frame.
void setFrustum(const Frustum<T> &frustum, const Matrix44<T> &cameraMat);
////////////////////////////////////////////////////////////////////
// isVisible()
// Check to see if shapes are visible.
bool isVisible(const Sphere3<T> &sphere) const;
bool isVisible(const Box<Vec3<T> > &box) const;
bool isVisible(const Vec3<T> &vec) const;
////////////////////////////////////////////////////////////////////
// completelyContains()
// Check to see if shapes are entirely contained.
bool completelyContains(const Sphere3<T> &sphere) const;
bool completelyContains(const Box<Vec3<T> > &box) const;
// These next items are kept primarily for debugging tools.
// It's useful for drawing the culling environment, and also
// for getting an "outside view" of the culling frustum.
IMATH_INTERNAL_NAMESPACE::Matrix44<T> cameraMat() const {return cameraMatrix;}
IMATH_INTERNAL_NAMESPACE::Frustum<T> currentFrustum() const {return currFrustum;}
protected:
// To understand why the planes are stored this way, see
// the SPECIAL NOTE above.
Vec3<T> planeNormX[2]; // The X compunents from 6 plane equations
Vec3<T> planeNormY[2]; // The Y compunents from 6 plane equations
Vec3<T> planeNormZ[2]; // The Z compunents from 6 plane equations
Vec3<T> planeOffsetVec[2]; // The distance offsets from 6 plane equations
// The absolute values are stored to assist with bounding box tests.
Vec3<T> planeNormAbsX[2]; // The abs(X) compunents from 6 plane equations
Vec3<T> planeNormAbsY[2]; // The abs(X) compunents from 6 plane equations
Vec3<T> planeNormAbsZ[2]; // The abs(X) compunents from 6 plane equations
// These are kept primarily for debugging tools.
Frustum<T> currFrustum;
Matrix44<T> cameraMatrix;
};
////////////////////////////////////////////////////////////////////
// setFrustum()
// This should usually only be called once per frame, or however
// often the camera moves.
template<class T>
void FrustumTest<T>::setFrustum(const Frustum<T> &frustum,
const Matrix44<T> &cameraMat)
{
Plane3<T> frustumPlanes[6];
frustum.planes(frustumPlanes, cameraMat);
// Here's where we effectively transpose the plane equations.
// We stuff all six X's into the two planeNormX vectors, etc.
for (int i = 0; i < 2; ++i)
{
int index = i * 3;
planeNormX[i] = Vec3<T>(frustumPlanes[index + 0].normal.x,
frustumPlanes[index + 1].normal.x,
frustumPlanes[index + 2].normal.x);
planeNormY[i] = Vec3<T>(frustumPlanes[index + 0].normal.y,
frustumPlanes[index + 1].normal.y,
frustumPlanes[index + 2].normal.y);
planeNormZ[i] = Vec3<T>(frustumPlanes[index + 0].normal.z,
frustumPlanes[index + 1].normal.z,
frustumPlanes[index + 2].normal.z);
planeNormAbsX[i] = Vec3<T>(IMATH_INTERNAL_NAMESPACE::abs(planeNormX[i].x),
IMATH_INTERNAL_NAMESPACE::abs(planeNormX[i].y),
IMATH_INTERNAL_NAMESPACE::abs(planeNormX[i].z));
planeNormAbsY[i] = Vec3<T>(IMATH_INTERNAL_NAMESPACE::abs(planeNormY[i].x),
IMATH_INTERNAL_NAMESPACE::abs(planeNormY[i].y),
IMATH_INTERNAL_NAMESPACE::abs(planeNormY[i].z));
planeNormAbsZ[i] = Vec3<T>(IMATH_INTERNAL_NAMESPACE::abs(planeNormZ[i].x),
IMATH_INTERNAL_NAMESPACE::abs(planeNormZ[i].y),
IMATH_INTERNAL_NAMESPACE::abs(planeNormZ[i].z));
planeOffsetVec[i] = Vec3<T>(frustumPlanes[index + 0].distance,
frustumPlanes[index + 1].distance,
frustumPlanes[index + 2].distance);
}
currFrustum = frustum;
cameraMatrix = cameraMat;
}
////////////////////////////////////////////////////////////////////
// isVisible(Sphere)
// Returns true if any part of the sphere is inside
// the frustum.
// The result MAY return close false-positives, but not false-negatives.
//
template<typename T>
bool FrustumTest<T>::isVisible(const Sphere3<T> &sphere) const
{
Vec3<T> center = sphere.center;
Vec3<T> radiusVec = Vec3<T>(sphere.radius, sphere.radius, sphere.radius);
// This is a vertical dot-product on three vectors at once.
Vec3<T> d0 = planeNormX[0] * center.x
+ planeNormY[0] * center.y
+ planeNormZ[0] * center.z
- radiusVec
- planeOffsetVec[0];
if (d0.x >= 0 || d0.y >= 0 || d0.z >= 0)
return false;
Vec3<T> d1 = planeNormX[1] * center.x
+ planeNormY[1] * center.y
+ planeNormZ[1] * center.z
- radiusVec
- planeOffsetVec[1];
if (d1.x >= 0 || d1.y >= 0 || d1.z >= 0)
return false;
return true;
}
////////////////////////////////////////////////////////////////////
// completelyContains(Sphere)
// Returns true if every part of the sphere is inside
// the frustum.
// The result MAY return close false-negatives, but not false-positives.
//
template<typename T>
bool FrustumTest<T>::completelyContains(const Sphere3<T> &sphere) const
{
Vec3<T> center = sphere.center;
Vec3<T> radiusVec = Vec3<T>(sphere.radius, sphere.radius, sphere.radius);
// This is a vertical dot-product on three vectors at once.
Vec3<T> d0 = planeNormX[0] * center.x
+ planeNormY[0] * center.y
+ planeNormZ[0] * center.z
+ radiusVec
- planeOffsetVec[0];
if (d0.x >= 0 || d0.y >= 0 || d0.z >= 0)
return false;
Vec3<T> d1 = planeNormX[1] * center.x
+ planeNormY[1] * center.y
+ planeNormZ[1] * center.z
+ radiusVec
- planeOffsetVec[1];
if (d1.x >= 0 || d1.y >= 0 || d1.z >= 0)
return false;
return true;
}
////////////////////////////////////////////////////////////////////
// isVisible(Box)
// Returns true if any part of the axis-aligned box
// is inside the frustum.
// The result MAY return close false-positives, but not false-negatives.
//
template<typename T>
bool FrustumTest<T>::isVisible(const Box<Vec3<T> > &box) const
{
if (box.isEmpty())
return false;
Vec3<T> center = (box.min + box.max) / 2;
Vec3<T> extent = (box.max - center);
// This is a vertical dot-product on three vectors at once.
Vec3<T> d0 = planeNormX[0] * center.x
+ planeNormY[0] * center.y
+ planeNormZ[0] * center.z
- planeNormAbsX[0] * extent.x
- planeNormAbsY[0] * extent.y
- planeNormAbsZ[0] * extent.z
- planeOffsetVec[0];
if (d0.x >= 0 || d0.y >= 0 || d0.z >= 0)
return false;
Vec3<T> d1 = planeNormX[1] * center.x
+ planeNormY[1] * center.y
+ planeNormZ[1] * center.z
- planeNormAbsX[1] * extent.x
- planeNormAbsY[1] * extent.y
- planeNormAbsZ[1] * extent.z
- planeOffsetVec[1];
if (d1.x >= 0 || d1.y >= 0 || d1.z >= 0)
return false;
return true;
}
////////////////////////////////////////////////////////////////////
// completelyContains(Box)
// Returns true if every part of the axis-aligned box
// is inside the frustum.
// The result MAY return close false-negatives, but not false-positives.
//
template<typename T>
bool FrustumTest<T>::completelyContains(const Box<Vec3<T> > &box) const
{
if (box.isEmpty())
return false;
Vec3<T> center = (box.min + box.max) / 2;
Vec3<T> extent = (box.max - center);
// This is a vertical dot-product on three vectors at once.
Vec3<T> d0 = planeNormX[0] * center.x
+ planeNormY[0] * center.y
+ planeNormZ[0] * center.z
+ planeNormAbsX[0] * extent.x
+ planeNormAbsY[0] * extent.y
+ planeNormAbsZ[0] * extent.z
- planeOffsetVec[0];
if (d0.x >= 0 || d0.y >= 0 || d0.z >= 0)
return false;
Vec3<T> d1 = planeNormX[1] * center.x
+ planeNormY[1] * center.y
+ planeNormZ[1] * center.z
+ planeNormAbsX[1] * extent.x
+ planeNormAbsY[1] * extent.y
+ planeNormAbsZ[1] * extent.z
- planeOffsetVec[1];
if (d1.x >= 0 || d1.y >= 0 || d1.z >= 0)
return false;
return true;
}
////////////////////////////////////////////////////////////////////
// isVisible(Vec3)
// Returns true if the point is inside the frustum.
//
template<typename T>
bool FrustumTest<T>::isVisible(const Vec3<T> &vec) const
{
// This is a vertical dot-product on three vectors at once.
Vec3<T> d0 = (planeNormX[0] * vec.x)
+ (planeNormY[0] * vec.y)
+ (planeNormZ[0] * vec.z)
- planeOffsetVec[0];
if (d0.x >= 0 || d0.y >= 0 || d0.z >= 0)
return false;
Vec3<T> d1 = (planeNormX[1] * vec.x)
+ (planeNormY[1] * vec.y)
+ (planeNormZ[1] * vec.z)
- planeOffsetVec[1];
if (d1.x >= 0 || d1.y >= 0 || d1.z >= 0)
return false;
return true;
}
typedef FrustumTest<float> FrustumTestf;
typedef FrustumTest<double> FrustumTestd;
IMATH_INTERNAL_NAMESPACE_HEADER_EXIT
#endif // INCLUDED_IMATHFRUSTUMTEST_H
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