BansheeEngine/CamelotRenderer/Source/CmFrustum.cpp

/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org

Copyright (c) 2000-2011 Torus Knot Software Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-----------------------------------------------------------------------------
*/

#include "CmFrustum.h"

#include "CmMath.h"
#include "CmMatrix3.h"
#include "CmSphere.h"
#include "CmException.h"
#include "CmHardwareBufferManager.h"
#include "CmHardwareVertexBuffer.h"
#include "CmHardwareIndexBuffer.h"
#include "CmRenderSystem.h"
#include "CmRenderSystemManager.h"

namespace CamelotEngine {
    const float Frustum::INFINITE_FAR_PLANE_ADJUST = 0.00001f;
    //-----------------------------------------------------------------------
    Frustum::Frustum(const String& name) : 
        mProjType(PT_PERSPECTIVE), 
        mFOVy(Radian(Math::PI/4.0f)), 
        mFarDist(100000.0f), 
        mNearDist(100.0f), 
        mAspect(1.33333333333333f), 
		mOrthoHeight(1000),
        mFrustumOffset(Vector2::ZERO),
        mFocalLength(1.0f),
        mLastParentOrientation(Quaternion::IDENTITY),
        mLastParentPosition(Vector3::ZERO),
        mRecalcFrustum(true), 
        mRecalcView(true), 
        mRecalcFrustumPlanes(true),
        mRecalcWorldSpaceCorners(true),
        mRecalcVertexData(true),
		mCustomViewMatrix(false),
		mCustomProjMatrix(false),
		mFrustumExtentsManuallySet(false)
    {
        updateView();
        updateFrustum();
    }

    //-----------------------------------------------------------------------
    Frustum::~Frustum()
    {
        // Do nothing
    }

    //-----------------------------------------------------------------------
    void Frustum::setFOVy(const Radian& fov)
    {
        mFOVy = fov;
        invalidateFrustum();
    }

    //-----------------------------------------------------------------------
    const Radian& Frustum::getFOVy(void) const
    {
        return mFOVy;
    }


    //-----------------------------------------------------------------------
    void Frustum::setFarClipDistance(float farPlane)
    {
        mFarDist = farPlane;
        invalidateFrustum();
    }

    //-----------------------------------------------------------------------
    float Frustum::getFarClipDistance(void) const
    {
        return mFarDist;
    }

    //-----------------------------------------------------------------------
    void Frustum::setNearClipDistance(float nearPlane)
    {
        if (nearPlane <= 0)
		{
            CM_EXCEPT(InvalidParametersException, "Near clip distance must be greater than zero.");
		}
        mNearDist = nearPlane;
        invalidateFrustum();
    }

    //-----------------------------------------------------------------------
    float Frustum::getNearClipDistance(void) const
    {
        return mNearDist;
    }

    //---------------------------------------------------------------------
    void Frustum::setFrustumOffset(const Vector2& offset)
    {
        mFrustumOffset = offset;
        invalidateFrustum();
    }
    //---------------------------------------------------------------------
    void Frustum::setFrustumOffset(float horizontal, float vertical)
    {
        setFrustumOffset(Vector2(horizontal, vertical));
    }
    //---------------------------------------------------------------------
    const Vector2& Frustum::getFrustumOffset() const
    {
        return mFrustumOffset;
    }
    //---------------------------------------------------------------------
    void Frustum::setFocalLength(float focalLength)
    {
        if (focalLength <= 0)
        {
            CM_EXCEPT(InvalidParametersException,
                "Focal length must be greater than zero.");
        }

        mFocalLength = focalLength;
        invalidateFrustum();
    }
    //---------------------------------------------------------------------
    float Frustum::getFocalLength() const
    {
        return mFocalLength;
    }
    //-----------------------------------------------------------------------
    const Matrix4& Frustum::getProjectionMatrix(void) const
    {

        updateFrustum();

        return mProjMatrix;
    }
    //-----------------------------------------------------------------------
    const Matrix4& Frustum::getProjectionMatrixWithRSDepth(void) const
    {

        updateFrustum();

        return mProjMatrixRSDepth;
    }
    //-----------------------------------------------------------------------
    const Matrix4& Frustum::getProjectionMatrixRS(void) const
    {

        updateFrustum();

        return mProjMatrixRS;
    }
    //-----------------------------------------------------------------------
    const Matrix4& Frustum::getViewMatrix(void) const
    {
        updateView();

        return mViewMatrix;

    }

    //-----------------------------------------------------------------------
    const Plane* Frustum::getFrustumPlanes(void) const
    {
        // Make any pending updates to the calculated frustum planes
        updateFrustumPlanes();

        return mFrustumPlanes;
    }

    //-----------------------------------------------------------------------
    const Plane& Frustum::getFrustumPlane(unsigned short plane) const
    {
        // Make any pending updates to the calculated frustum planes
        updateFrustumPlanes();

        return mFrustumPlanes[plane];

    }

    //-----------------------------------------------------------------------
    bool Frustum::isVisible(const AxisAlignedBox& bound, FrustumPlane* culledBy) const
    {
        // Null boxes always invisible
        if (bound.isNull()) return false;

        // Infinite boxes always visible
        if (bound.isInfinite()) return true;

        // Make any pending updates to the calculated frustum planes
        updateFrustumPlanes();

        // Get centre of the box
        Vector3 centre = bound.getCenter();
        // Get the half-size of the box
        Vector3 halfSize = bound.getHalfSize();

        // For each plane, see if all points are on the negative side
        // If so, object is not visible
        for (int plane = 0; plane < 6; ++plane)
        {
            // Skip far plane if infinite view frustum
            if (plane == FRUSTUM_PLANE_FAR && mFarDist == 0)
                continue;

            Plane::Side side = mFrustumPlanes[plane].getSide(centre, halfSize);
            if (side == Plane::NEGATIVE_SIDE)
            {
                // ALL corners on negative side therefore out of view
                if (culledBy)
                    *culledBy = (FrustumPlane)plane;
                return false;
            }

        }

        return true;
    }

    //-----------------------------------------------------------------------
    bool Frustum::isVisible(const Vector3& vert, FrustumPlane* culledBy) const
    {
        // Make any pending updates to the calculated frustum planes
        updateFrustumPlanes();

        // For each plane, see if all points are on the negative side
        // If so, object is not visible
        for (int plane = 0; plane < 6; ++plane)
        {
            // Skip far plane if infinite view frustum
            if (plane == FRUSTUM_PLANE_FAR && mFarDist == 0)
                continue;

            if (mFrustumPlanes[plane].getSide(vert) == Plane::NEGATIVE_SIDE)
            {
                // ALL corners on negative side therefore out of view
                if (culledBy)
                    *culledBy = (FrustumPlane)plane;
                return false;
            }

        }

        return true;
    }
    //-----------------------------------------------------------------------
    bool Frustum::isVisible(const Sphere& sphere, FrustumPlane* culledBy) const
    {
        // Make any pending updates to the calculated frustum planes
        updateFrustumPlanes();

        // For each plane, see if sphere is on negative side
        // If so, object is not visible
        for (int plane = 0; plane < 6; ++plane)
        {
            // Skip far plane if infinite view frustum
            if (plane == FRUSTUM_PLANE_FAR && mFarDist == 0)
                continue;

            // If the distance from sphere center to plane is negative, and 'more negative' 
            // than the radius of the sphere, sphere is outside frustum
            if (mFrustumPlanes[plane].getDistance(sphere.getCenter()) < -sphere.getRadius())
            {
                // ALL corners on negative side therefore out of view
                if (culledBy)
                    *culledBy = (FrustumPlane)plane;
                return false;
            }

        }

        return true;
    }
    //-----------------------------------------------------------------------
    void Frustum::calcProjectionParameters(float& left, float& right, float& bottom, float& top) const
    { 
		if (mCustomProjMatrix)
		{
			// Convert clipspace corners to camera space
			Matrix4 invProj = mProjMatrix.inverse();
			Vector3 topLeft(-0.5f, 0.5f, 0.0f);
			Vector3 bottomRight(0.5f, -0.5f, 0.0f);

			topLeft = invProj * topLeft;
			bottomRight = invProj * bottomRight;

			left = topLeft.x;
			top = topLeft.y;
			right = bottomRight.x;
			bottom = bottomRight.y;

		}
		else
		{
			if (mFrustumExtentsManuallySet)
			{
				left = mLeft;
				right = mRight;
				top = mTop;
				bottom = mBottom;
			}
			// Calculate general projection parameters
			else if (mProjType == PT_PERSPECTIVE)
			{
				Radian thetaY (mFOVy * 0.5f);
				float tanThetaY = Math::Tan(thetaY);
				float tanThetaX = tanThetaY * mAspect;

				float nearFocal = mNearDist / mFocalLength;
				float nearOffsetX = mFrustumOffset.x * nearFocal;
				float nearOffsetY = mFrustumOffset.y * nearFocal;
				float half_w = tanThetaX * mNearDist;
				float half_h = tanThetaY * mNearDist;

				left   = - half_w + nearOffsetX;
				right  = + half_w + nearOffsetX;
				bottom = - half_h + nearOffsetY;
				top    = + half_h + nearOffsetY;

				mLeft = left;
				mRight = right;
				mTop = top;
				mBottom = bottom;
			}
			else
			{
				// Unknown how to apply frustum offset to orthographic camera, just ignore here
				float half_w = getOrthoWindowWidth() * 0.5f;
				float half_h = getOrthoWindowHeight() * 0.5f;

				left   = - half_w;
				right  = + half_w;
				bottom = - half_h;
				top    = + half_h;

				mLeft = left;
				mRight = right;
				mTop = top;
				mBottom = bottom;
			}

		}
    }
	//-----------------------------------------------------------------------
	void Frustum::updateFrustumImpl(void) const
	{
		// Common calcs
		float left, right, bottom, top;

        calcProjectionParameters(left, right, bottom, top);

		if (!mCustomProjMatrix)
		{

			// The code below will dealing with general projection 
			// parameters, similar glFrustum and glOrtho.
			// Doesn't optimise manually except division operator, so the 
			// code more self-explaining.

			float inv_w = 1 / (right - left);
			float inv_h = 1 / (top - bottom);
			float inv_d = 1 / (mFarDist - mNearDist);

			// Recalc if frustum params changed
			if (mProjType == PT_PERSPECTIVE)
			{
				// Calc matrix elements
				float A = 2 * mNearDist * inv_w;
				float B = 2 * mNearDist * inv_h;
				float C = (right + left) * inv_w;
				float D = (top + bottom) * inv_h;
				float q, qn;
				if (mFarDist == 0)
				{
					// Infinite far plane
					q = Frustum::INFINITE_FAR_PLANE_ADJUST - 1;
					qn = mNearDist * (Frustum::INFINITE_FAR_PLANE_ADJUST - 2);
				}
				else
				{
					q = - (mFarDist + mNearDist) * inv_d;
					qn = -2 * (mFarDist * mNearDist) * inv_d;
				}

				// NB: This creates 'uniform' perspective projection matrix,
				// which depth range [-1,1], right-handed rules
				//
				// [ A   0   C   0  ]
				// [ 0   B   D   0  ]
				// [ 0   0   q   qn ]
				// [ 0   0   -1  0  ]
				//
				// A = 2 * near / (right - left)
				// B = 2 * near / (top - bottom)
				// C = (right + left) / (right - left)
				// D = (top + bottom) / (top - bottom)
				// q = - (far + near) / (far - near)
				// qn = - 2 * (far * near) / (far - near)

				mProjMatrix = Matrix4::ZERO;
				mProjMatrix[0][0] = A;
				mProjMatrix[0][2] = C;
				mProjMatrix[1][1] = B;
				mProjMatrix[1][2] = D;
				mProjMatrix[2][2] = q;
				mProjMatrix[2][3] = qn;
				mProjMatrix[3][2] = -1;
			} // perspective
			else if (mProjType == PT_ORTHOGRAPHIC)
			{
				float A = 2 * inv_w;
				float B = 2 * inv_h;
				float C = - (right + left) * inv_w;
				float D = - (top + bottom) * inv_h;
				float q, qn;
				if (mFarDist == 0)
				{
					// Can not do infinite far plane here, avoid divided zero only
					q = - Frustum::INFINITE_FAR_PLANE_ADJUST / mNearDist;
					qn = - Frustum::INFINITE_FAR_PLANE_ADJUST - 1;
				}
				else
				{
					q = - 2 * inv_d;
					qn = - (mFarDist + mNearDist)  * inv_d;
				}

				// NB: This creates 'uniform' orthographic projection matrix,
				// which depth range [-1,1], right-handed rules
				//
				// [ A   0   0   C  ]
				// [ 0   B   0   D  ]
				// [ 0   0   q   qn ]
				// [ 0   0   0   1  ]
				//
				// A = 2 * / (right - left)
				// B = 2 * / (top - bottom)
				// C = - (right + left) / (right - left)
				// D = - (top + bottom) / (top - bottom)
				// q = - 2 / (far - near)
				// qn = - (far + near) / (far - near)

				mProjMatrix = Matrix4::ZERO;
				mProjMatrix[0][0] = A;
				mProjMatrix[0][3] = C;
				mProjMatrix[1][1] = B;
				mProjMatrix[1][3] = D;
				mProjMatrix[2][2] = q;
				mProjMatrix[2][3] = qn;
				mProjMatrix[3][3] = 1;
			} // ortho            
		} // !mCustomProjMatrix

		RenderSystem* renderSystem = CamelotEngine::RenderSystemManager::getActive();
		// API specific
		renderSystem->_convertProjectionMatrix(mProjMatrix, mProjMatrixRS);
		// API specific for Gpu Programs
		renderSystem->_convertProjectionMatrix(mProjMatrix, mProjMatrixRSDepth, true);


		// Calculate bounding box (local)
		// Box is from 0, down -Z, max dimensions as determined from far plane
		// If infinite view frustum just pick a far value
		float farDist = (mFarDist == 0) ? 100000 : mFarDist;
		// Near plane bounds
		Vector3 min(left, bottom, -farDist);
		Vector3 max(right, top, 0);

		if (mCustomProjMatrix)
		{
			// Some custom projection matrices can have unusual inverted settings
			// So make sure the AABB is the right way around to start with
			Vector3 tmp = min;
			min.makeFloor(max);
			max.makeCeil(tmp);
		}

		if (mProjType == PT_PERSPECTIVE)
		{
			// Merge with far plane bounds
			float radio = farDist / mNearDist;
			min.makeFloor(Vector3(left * radio, bottom * radio, -farDist));
			max.makeCeil(Vector3(right * radio, top * radio, 0));
		}
		mBoundingBox.setExtents(min, max);

		mRecalcFrustum = false;

		// Signal to update frustum clipping planes
		mRecalcFrustumPlanes = true;
	}
    //-----------------------------------------------------------------------
    void Frustum::updateFrustum(void) const
    {
        if (isFrustumOutOfDate())
        {
			updateFrustumImpl();
        }
    }

    //-----------------------------------------------------------------------
    void Frustum::updateVertexData(void) const
    {
        if (mRecalcVertexData)
        {
            if (mVertexData.vertexBufferBinding->getBufferCount() <= 0)
            {
                // Initialise vertex & index data
                mVertexData.vertexDeclaration->addElement(0, 0, VET_FLOAT3, VES_POSITION);
                mVertexData.vertexCount = 32;
                mVertexData.vertexStart = 0;
                mVertexData.vertexBufferBinding->setBinding( 0,
                    HardwareBufferManager::getSingleton().createVertexBuffer(
                        sizeof(float)*3, 32, HardwareBuffer::HBU_DYNAMIC_WRITE_ONLY) );
            }

            // Note: Even though we can dealing with general projection matrix here,
            //       but because it's incompatibly with infinite far plane, thus, we
            //       still need to working with projection parameters.

            // Calc near plane corners
            float vpLeft, vpRight, vpBottom, vpTop;
            calcProjectionParameters(vpLeft, vpRight, vpBottom, vpTop);

            // Treat infinite fardist as some arbitrary far value
            float farDist = (mFarDist == 0) ? 100000 : mFarDist;

            // Calc far plane corners
            float radio = mProjType == PT_PERSPECTIVE ? farDist / mNearDist : 1;
            float farLeft = vpLeft * radio;
            float farRight = vpRight * radio;
            float farBottom = vpBottom * radio;
            float farTop = vpTop * radio;

            // Calculate vertex positions (local)
            // 0 is the origin
            // 1, 2, 3, 4 are the points on the near plane, top left first, clockwise
            // 5, 6, 7, 8 are the points on the far plane, top left first, clockwise
            HardwareVertexBufferPtr vbuf = mVertexData.vertexBufferBinding->getBuffer(0);
            float* pFloat = static_cast<float*>(vbuf->lock(HardwareBuffer::HBL_DISCARD));

            // near plane (remember frustum is going in -Z direction)
            *pFloat++ = vpLeft;  *pFloat++ = vpTop;    *pFloat++ = -mNearDist;
            *pFloat++ = vpRight; *pFloat++ = vpTop;    *pFloat++ = -mNearDist;

            *pFloat++ = vpRight; *pFloat++ = vpTop;    *pFloat++ = -mNearDist;
            *pFloat++ = vpRight; *pFloat++ = vpBottom; *pFloat++ = -mNearDist;

            *pFloat++ = vpRight; *pFloat++ = vpBottom; *pFloat++ = -mNearDist;
            *pFloat++ = vpLeft;  *pFloat++ = vpBottom; *pFloat++ = -mNearDist;

            *pFloat++ = vpLeft;  *pFloat++ = vpBottom; *pFloat++ = -mNearDist;
            *pFloat++ = vpLeft;  *pFloat++ = vpTop;    *pFloat++ = -mNearDist;

            // far plane (remember frustum is going in -Z direction)
            *pFloat++ = farLeft;  *pFloat++ = farTop;    *pFloat++ = -farDist;
            *pFloat++ = farRight; *pFloat++ = farTop;    *pFloat++ = -farDist;

            *pFloat++ = farRight; *pFloat++ = farTop;    *pFloat++ = -farDist;
            *pFloat++ = farRight; *pFloat++ = farBottom; *pFloat++ = -farDist;

            *pFloat++ = farRight; *pFloat++ = farBottom; *pFloat++ = -farDist;
            *pFloat++ = farLeft;  *pFloat++ = farBottom; *pFloat++ = -farDist;

            *pFloat++ = farLeft;  *pFloat++ = farBottom; *pFloat++ = -farDist;
            *pFloat++ = farLeft;  *pFloat++ = farTop;    *pFloat++ = -farDist;

            // Sides of the pyramid
            *pFloat++ = 0.0f;    *pFloat++ = 0.0f;   *pFloat++ = 0.0f;
            *pFloat++ = vpLeft;  *pFloat++ = vpTop;  *pFloat++ = -mNearDist;

            *pFloat++ = 0.0f;    *pFloat++ = 0.0f;   *pFloat++ = 0.0f;
            *pFloat++ = vpRight; *pFloat++ = vpTop;    *pFloat++ = -mNearDist;

            *pFloat++ = 0.0f;    *pFloat++ = 0.0f;   *pFloat++ = 0.0f;
            *pFloat++ = vpRight; *pFloat++ = vpBottom; *pFloat++ = -mNearDist;

            *pFloat++ = 0.0f;    *pFloat++ = 0.0f;   *pFloat++ = 0.0f;
            *pFloat++ = vpLeft;  *pFloat++ = vpBottom; *pFloat++ = -mNearDist;

            // Sides of the box

            *pFloat++ = vpLeft;  *pFloat++ = vpTop;  *pFloat++ = -mNearDist;
            *pFloat++ = farLeft;  *pFloat++ = farTop;  *pFloat++ = -farDist;

            *pFloat++ = vpRight; *pFloat++ = vpTop;    *pFloat++ = -mNearDist;
            *pFloat++ = farRight; *pFloat++ = farTop;    *pFloat++ = -farDist;

            *pFloat++ = vpRight; *pFloat++ = vpBottom; *pFloat++ = -mNearDist;
            *pFloat++ = farRight; *pFloat++ = farBottom; *pFloat++ = -farDist;

            *pFloat++ = vpLeft;  *pFloat++ = vpBottom; *pFloat++ = -mNearDist;
            *pFloat++ = farLeft;  *pFloat++ = farBottom; *pFloat++ = -farDist;


            vbuf->unlock();

            mRecalcVertexData = false;
        }
    }

    //-----------------------------------------------------------------------
    bool Frustum::isViewOutOfDate(void) const
    {
        // Attached to node?
		// TODO PORT - Not attached to node because I'll be handling this differently
        //if (mParentNode)
        //{
        //    if (mRecalcView ||
        //        mParentNode->_getDerivedOrientation() != mLastParentOrientation ||
        //        mParentNode->_getDerivedPosition() != mLastParentPosition)
        //    {
        //        // Ok, we're out of date with SceneNode we're attached to
        //        mLastParentOrientation = mParentNode->_getDerivedOrientation();
        //        mLastParentPosition = mParentNode->_getDerivedPosition();
        //        mRecalcView = true;
        //    }
        //}

        return mRecalcView;
    }

    //-----------------------------------------------------------------------
    bool Frustum::isFrustumOutOfDate(void) const
    {
        return mRecalcFrustum;
    }

    //-----------------------------------------------------------------------
	void Frustum::updateViewImpl(void) const
	{
		// ----------------------
		// Update the view matrix
		// ----------------------

		// Get orientation from quaternion

		if (!mCustomViewMatrix)
		{
			Matrix3 rot;
			const Quaternion& orientation = getOrientationForViewUpdate();
			const Vector3& position = getPositionForViewUpdate();

			mViewMatrix = Math::makeViewMatrix(position, orientation, 0);
		}

		mRecalcView = false;

		// Signal to update frustum clipping planes
		mRecalcFrustumPlanes = true;
		// Signal to update world space corners
		mRecalcWorldSpaceCorners = true;
	}
	//---------------------------------------------------------------------
	void Frustum::calcViewMatrixRelative(const Vector3& relPos, Matrix4& matToUpdate) const
	{
		Matrix4 matTrans = Matrix4::IDENTITY;
		matTrans.setTrans(relPos);
		matToUpdate = getViewMatrix() * matTrans;

	}
	//-----------------------------------------------------------------------
    void Frustum::updateView(void) const
    {
        if (isViewOutOfDate())
        {
			updateViewImpl();
        }
    }

	//-----------------------------------------------------------------------
	void Frustum::updateFrustumPlanesImpl(void) const
	{
		// -------------------------
		// Update the frustum planes
		// -------------------------
		Matrix4 combo = mProjMatrix * mViewMatrix;

		mFrustumPlanes[FRUSTUM_PLANE_LEFT].normal.x = combo[3][0] + combo[0][0];
		mFrustumPlanes[FRUSTUM_PLANE_LEFT].normal.y = combo[3][1] + combo[0][1];
		mFrustumPlanes[FRUSTUM_PLANE_LEFT].normal.z = combo[3][2] + combo[0][2];
		mFrustumPlanes[FRUSTUM_PLANE_LEFT].d = combo[3][3] + combo[0][3];

		mFrustumPlanes[FRUSTUM_PLANE_RIGHT].normal.x = combo[3][0] - combo[0][0];
		mFrustumPlanes[FRUSTUM_PLANE_RIGHT].normal.y = combo[3][1] - combo[0][1];
		mFrustumPlanes[FRUSTUM_PLANE_RIGHT].normal.z = combo[3][2] - combo[0][2];
		mFrustumPlanes[FRUSTUM_PLANE_RIGHT].d = combo[3][3] - combo[0][3];

		mFrustumPlanes[FRUSTUM_PLANE_TOP].normal.x = combo[3][0] - combo[1][0];
		mFrustumPlanes[FRUSTUM_PLANE_TOP].normal.y = combo[3][1] - combo[1][1];
		mFrustumPlanes[FRUSTUM_PLANE_TOP].normal.z = combo[3][2] - combo[1][2];
		mFrustumPlanes[FRUSTUM_PLANE_TOP].d = combo[3][3] - combo[1][3];

		mFrustumPlanes[FRUSTUM_PLANE_BOTTOM].normal.x = combo[3][0] + combo[1][0];
		mFrustumPlanes[FRUSTUM_PLANE_BOTTOM].normal.y = combo[3][1] + combo[1][1];
		mFrustumPlanes[FRUSTUM_PLANE_BOTTOM].normal.z = combo[3][2] + combo[1][2];
		mFrustumPlanes[FRUSTUM_PLANE_BOTTOM].d = combo[3][3] + combo[1][3];

		mFrustumPlanes[FRUSTUM_PLANE_NEAR].normal.x = combo[3][0] + combo[2][0];
		mFrustumPlanes[FRUSTUM_PLANE_NEAR].normal.y = combo[3][1] + combo[2][1];
		mFrustumPlanes[FRUSTUM_PLANE_NEAR].normal.z = combo[3][2] + combo[2][2];
		mFrustumPlanes[FRUSTUM_PLANE_NEAR].d = combo[3][3] + combo[2][3];

		mFrustumPlanes[FRUSTUM_PLANE_FAR].normal.x = combo[3][0] - combo[2][0];
		mFrustumPlanes[FRUSTUM_PLANE_FAR].normal.y = combo[3][1] - combo[2][1];
		mFrustumPlanes[FRUSTUM_PLANE_FAR].normal.z = combo[3][2] - combo[2][2];
		mFrustumPlanes[FRUSTUM_PLANE_FAR].d = combo[3][3] - combo[2][3];

		// Renormalise any normals which were not unit length
		for(int i=0; i<6; i++ ) 
		{
			float length = mFrustumPlanes[i].normal.normalise();
			mFrustumPlanes[i].d /= length;
		}

		mRecalcFrustumPlanes = false;
	}
    //-----------------------------------------------------------------------
    void Frustum::updateFrustumPlanes(void) const
    {
        updateView();
        updateFrustum();

        if (mRecalcFrustumPlanes)
        {
			updateFrustumPlanesImpl();
        }
    }
	//-----------------------------------------------------------------------
	void Frustum::updateWorldSpaceCornersImpl(void) const
	{
		Matrix4 eyeToWorld = mViewMatrix.inverseAffine();

		// Note: Even though we can dealing with general projection matrix here,
		//       but because it's incompatibly with infinite far plane, thus, we
		//       still need to working with projection parameters.

		// Calc near plane corners
		float nearLeft, nearRight, nearBottom, nearTop;
		calcProjectionParameters(nearLeft, nearRight, nearBottom, nearTop);

		// Treat infinite fardist as some arbitrary far value
		float farDist = (mFarDist == 0) ? 100000 : mFarDist;

		// Calc far palne corners
		float radio = mProjType == PT_PERSPECTIVE ? farDist / mNearDist : 1;
		float farLeft = nearLeft * radio;
		float farRight = nearRight * radio;
		float farBottom = nearBottom * radio;
		float farTop = nearTop * radio;

		// near
		mWorldSpaceCorners[0] = eyeToWorld.transformAffine(Vector3(nearRight, nearTop,    -mNearDist));
		mWorldSpaceCorners[1] = eyeToWorld.transformAffine(Vector3(nearLeft,  nearTop,    -mNearDist));
		mWorldSpaceCorners[2] = eyeToWorld.transformAffine(Vector3(nearLeft,  nearBottom, -mNearDist));
		mWorldSpaceCorners[3] = eyeToWorld.transformAffine(Vector3(nearRight, nearBottom, -mNearDist));
		// far
		mWorldSpaceCorners[4] = eyeToWorld.transformAffine(Vector3(farRight,  farTop,     -farDist));
		mWorldSpaceCorners[5] = eyeToWorld.transformAffine(Vector3(farLeft,   farTop,     -farDist));
		mWorldSpaceCorners[6] = eyeToWorld.transformAffine(Vector3(farLeft,   farBottom,  -farDist));
		mWorldSpaceCorners[7] = eyeToWorld.transformAffine(Vector3(farRight,  farBottom,  -farDist));


		mRecalcWorldSpaceCorners = false;
	}
    //-----------------------------------------------------------------------
    void Frustum::updateWorldSpaceCorners(void) const
    {
        updateView();

        if (mRecalcWorldSpaceCorners)
        {
			updateWorldSpaceCornersImpl();
        }

    }

    //-----------------------------------------------------------------------
    float Frustum::getAspectRatio(void) const
    {
        return mAspect;
    }

    //-----------------------------------------------------------------------
    void Frustum::setAspectRatio(float r)
    {
        mAspect = r;
        invalidateFrustum();
    }

    //-----------------------------------------------------------------------
    const AxisAlignedBox& Frustum::getBoundingBox(void) const
    {
        return mBoundingBox;
    }
    //-----------------------------------------------------------------------
	float Frustum::getBoundingRadius(void) const
	{
        return (mFarDist == 0)? 100000 : mFarDist;
	}
    // -------------------------------------------------------------------
    void Frustum::invalidateFrustum() const
    {
        mRecalcFrustum = true;
        mRecalcFrustumPlanes = true;
        mRecalcWorldSpaceCorners = true;
        mRecalcVertexData = true;
    }
    // -------------------------------------------------------------------
    void Frustum::invalidateView() const
    {
        mRecalcView = true;
        mRecalcFrustumPlanes = true;
        mRecalcWorldSpaceCorners = true;
    }
    // -------------------------------------------------------------------
    const Vector3* Frustum::getWorldSpaceCorners(void) const
    {
        updateWorldSpaceCorners();

        return mWorldSpaceCorners;
    }
    //-----------------------------------------------------------------------
    void Frustum::setProjectionType(ProjectionType pt)
    {
        mProjType = pt;
        invalidateFrustum();
    }

    //-----------------------------------------------------------------------
    ProjectionType Frustum::getProjectionType(void) const
    {
        return mProjType;
    }
    //-----------------------------------------------------------------------
    const Vector3& Frustum::getPositionForViewUpdate(void) const
    {
        return mLastParentPosition;
    }
    //-----------------------------------------------------------------------
    const Quaternion& Frustum::getOrientationForViewUpdate(void) const
    {
        return mLastParentOrientation;
    }
    //---------------------------------------------------------------------
    bool Frustum::projectSphere(const Sphere& sphere, 
        float* left, float* top, float* right, float* bottom) const
    {
		// See http://www.gamasutra.com/features/20021011/lengyel_06.htm
        // Transform light position into camera space

        updateView();
        Vector3 eyeSpacePos = mViewMatrix.transformAffine(sphere.getCenter());

		// initialise
		*left = *bottom = -1.0f;
		*right = *top = 1.0f;

        if (eyeSpacePos.z < 0)
        {
			updateFrustum();
			const Matrix4& projMatrix = getProjectionMatrix();
            float r = sphere.getRadius();
			float rsq = r * r;

            // early-exit
            if (eyeSpacePos.squaredLength() <= rsq)
                return false;

			float Lxz = Math::Sqr(eyeSpacePos.x) + Math::Sqr(eyeSpacePos.z);
			float Lyz = Math::Sqr(eyeSpacePos.y) + Math::Sqr(eyeSpacePos.z);

			// Find the tangent planes to the sphere
			// XZ first
			// calculate quadratic discriminant: b*b - 4ac
			// x = Nx
			// a = Lx^2 + Lz^2
			// b = -2rLx
			// c = r^2 - Lz^2
			float a = Lxz;
			float b = -2.0f * r * eyeSpacePos.x;
			float c = rsq - Math::Sqr(eyeSpacePos.z);
			float D = b*b - 4.0f*a*c;

			// two roots?
			if (D > 0)
			{
				float sqrootD = Math::Sqrt(D);
				// solve the quadratic to get the components of the normal
				float Nx0 = (-b + sqrootD) / (2 * a);
				float Nx1 = (-b - sqrootD) / (2 * a);
				
				// Derive Z from this
				float Nz0 = (r - Nx0 * eyeSpacePos.x) / eyeSpacePos.z;
				float Nz1 = (r - Nx1 * eyeSpacePos.x) / eyeSpacePos.z;

				// Get the point of tangency
				// Only consider points of tangency in front of the camera
				float Pz0 = (Lxz - rsq) / (eyeSpacePos.z - ((Nz0 / Nx0) * eyeSpacePos.x));
				if (Pz0 < 0)
				{
					// Project point onto near plane in worldspace
					float nearx0 = (Nz0 * mNearDist) / Nx0;
					// now we need to map this to viewport coords
					// use projection matrix since that will take into account all factors
					Vector3 relx0 = projMatrix * Vector3(nearx0, 0, -mNearDist);

					// find out whether this is a left side or right side
					float Px0 = -(Pz0 * Nz0) / Nx0;
					if (Px0 > eyeSpacePos.x)
					{
						*right = std::min(*right, relx0.x);
					}
					else
					{
						*left = std::max(*left, relx0.x);
					}
				}
				float Pz1 = (Lxz - rsq) / (eyeSpacePos.z - ((Nz1 / Nx1) * eyeSpacePos.x));
				if (Pz1 < 0)
				{
					// Project point onto near plane in worldspace
					float nearx1 = (Nz1 * mNearDist) / Nx1;
					// now we need to map this to viewport coords
					// use projection matrix since that will take into account all factors
					Vector3 relx1 = projMatrix * Vector3(nearx1, 0, -mNearDist);

					// find out whether this is a left side or right side
					float Px1 = -(Pz1 * Nz1) / Nx1;
					if (Px1 > eyeSpacePos.x)
					{
						*right = std::min(*right, relx1.x);
					}
					else
					{
						*left = std::max(*left, relx1.x);
					}
				}
			}


			// Now YZ 
			// calculate quadratic discriminant: b*b - 4ac
			// x = Ny
			// a = Ly^2 + Lz^2
			// b = -2rLy
			// c = r^2 - Lz^2
			a = Lyz;
			b = -2.0f * r * eyeSpacePos.y;
			c = rsq - Math::Sqr(eyeSpacePos.z);
			D = b*b - 4.0f*a*c;

			// two roots?
			if (D > 0)
			{
				float sqrootD = Math::Sqrt(D);
				// solve the quadratic to get the components of the normal
				float Ny0 = (-b + sqrootD) / (2 * a);
				float Ny1 = (-b - sqrootD) / (2 * a);

				// Derive Z from this
				float Nz0 = (r - Ny0 * eyeSpacePos.y) / eyeSpacePos.z;
				float Nz1 = (r - Ny1 * eyeSpacePos.y) / eyeSpacePos.z;

				// Get the point of tangency
				// Only consider points of tangency in front of the camera
				float Pz0 = (Lyz - rsq) / (eyeSpacePos.z - ((Nz0 / Ny0) * eyeSpacePos.y));
				if (Pz0 < 0)
				{
					// Project point onto near plane in worldspace
					float neary0 = (Nz0 * mNearDist) / Ny0;
					// now we need to map this to viewport coords
					// use projection matriy since that will take into account all factors
					Vector3 rely0 = projMatrix * Vector3(0, neary0, -mNearDist);

					// find out whether this is a top side or bottom side
					float Py0 = -(Pz0 * Nz0) / Ny0;
					if (Py0 > eyeSpacePos.y)
					{
						*top = std::min(*top, rely0.y);
					}
					else
					{
						*bottom = std::max(*bottom, rely0.y);
					}
				}
				float Pz1 = (Lyz - rsq) / (eyeSpacePos.z - ((Nz1 / Ny1) * eyeSpacePos.y));
				if (Pz1 < 0)
				{
					// Project point onto near plane in worldspace
					float neary1 = (Nz1 * mNearDist) / Ny1;
					// now we need to map this to viewport coords
					// use projection matriy since that will take into account all factors
					Vector3 rely1 = projMatrix * Vector3(0, neary1, -mNearDist);

					// find out whether this is a top side or bottom side
					float Py1 = -(Pz1 * Nz1) / Ny1;
					if (Py1 > eyeSpacePos.y)
					{
						*top = std::min(*top, rely1.y);
					}
					else
					{
						*bottom = std::max(*bottom, rely1.y);
					}
				}
			}
        }

        return (*left != -1.0f) || (*top != 1.0f) || (*right != 1.0f) || (*bottom != -1.0f);

    }
    //---------------------------------------------------------------------
	void Frustum::setCustomViewMatrix(bool enable, const Matrix4& viewMatrix)
	{
		mCustomViewMatrix = enable;
		if (enable)
		{
            assert(viewMatrix.isAffine());
			mViewMatrix = viewMatrix;
		}
		invalidateView();
	}
    //---------------------------------------------------------------------
	void Frustum::setCustomProjectionMatrix(bool enable, const Matrix4& projMatrix)
	{
		mCustomProjMatrix = enable;
		if (enable)
		{
			mProjMatrix = projMatrix;
		}
		invalidateFrustum();
	}
	//---------------------------------------------------------------------
	void Frustum::setOrthoWindow(float w, float h)
	{
		mOrthoHeight = h;
		mAspect = w / h;
		invalidateFrustum();
	}
	//---------------------------------------------------------------------
	void Frustum::setOrthoWindowHeight(float h)
	{
		mOrthoHeight = h;
		invalidateFrustum();
	}
	//---------------------------------------------------------------------
	void Frustum::setOrthoWindowWidth(float w)
	{
		mOrthoHeight = w / mAspect;
		invalidateFrustum();
	}
	//---------------------------------------------------------------------
	float Frustum::getOrthoWindowHeight() const
	{
		return mOrthoHeight;
	}
	//---------------------------------------------------------------------
	float Frustum::getOrthoWindowWidth() const
	{
		return mOrthoHeight * mAspect;	
	}
	//---------------------------------------------------------------------
	void Frustum::setFrustumExtents(float left, float right, float top, float bottom)
	{
		mFrustumExtentsManuallySet = true;
		mLeft = left;
		mRight = right;
		mTop = top;
		mBottom = bottom;

		invalidateFrustum();
	}
	//---------------------------------------------------------------------
	void Frustum::resetFrustumExtents()
	{
		mFrustumExtentsManuallySet = false;
		invalidateFrustum();
	}
	//---------------------------------------------------------------------
	void Frustum::getFrustumExtents(float& outleft, float& outright, float& outtop, float& outbottom) const
	{
		updateFrustum();
		outleft = mLeft;
		outright = mRight;
		outtop = mTop;
		outbottom = mBottom;
	}
} // namespace CamelotEngine