source: downloads/ogre/OgreMain/src/OgreShadowCameraSetupLiSPSM.cpp @ 17

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

Copyright (c) 2006  Torus Knot Software Ltd
Copyright (c) 2006 Matthias Fink, netAllied GmbH <matthias.fink@web.de>                                                         
Also see acknowledgements in Readme.html

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA, or go to
http://www.gnu.org/copyleft/lesser.txt.

You may alternatively use this source under the terms of a specific version of
the OGRE Unrestricted License provided you have obtained such a license from
Torus Knot Software Ltd.
-----------------------------------------------------------------------------
*/

#include "OgreStableHeaders.h"
#include "OgreShadowCameraSetupLiSPSM.h"
#include "OgreRoot.h"
#include "OgreSceneManager.h"
#include "OgreCamera.h"
#include "OgreLight.h"
#include "OgrePlane.h"
#include "OgreConvexBody.h"

namespace Ogre
{


        LiSPSMShadowCameraSetup::LiSPSMShadowCameraSetup(void)
                : mOptAdjustFactor(0.1f), mUseSimpleNOpt(true)
        {
        }
        //-----------------------------------------------------------------------
        LiSPSMShadowCameraSetup::~LiSPSMShadowCameraSetup(void)
        {
        }
        //-----------------------------------------------------------------------
        Matrix4 LiSPSMShadowCameraSetup::calculateLiSPSM(const Matrix4& lightSpace, 
                const PointListBody& bodyB, const PointListBody& bodyLVS,
                const SceneManager& sm, const Camera& cam, const Light& light) const
        {
                // set up bodyB AAB in light space
                AxisAlignedBox bodyBAAB_ls;
                for (size_t i = 0; i < bodyB.getPointCount(); ++i)
                {
                        bodyBAAB_ls.merge(lightSpace * bodyB.getPoint(i));
                }

                // near camera point in light space
                const Vector3 e_ls = lightSpace * getNearCameraPoint_ws(cam.getViewMatrix(), bodyLVS);

                // C_start has x and y of e and z from the bodyABB_ls (we look down the negative z axis, so take the maximum z value)
                const Vector3 C_start_ls(e_ls.x, e_ls.y, bodyBAAB_ls.getMaximum().z);

                // calculate the optimal distance between origin and near plane
                Real n_opt;

                if (mUseSimpleNOpt)
                        n_opt = calculateNOptSimple(bodyLVS, cam);
                else
                        n_opt = calculateNOpt(lightSpace, bodyBAAB_ls, bodyLVS, cam);

                // in case n_opt is null, uniform shadow mapping will be done
                if (n_opt <= 0.0)
                {
                        return Matrix4::IDENTITY;
                }

                // calculate the projection center C which is n units behind the near plane of P
                // we look into the negative z direction so add n
                const Vector3 C(C_start_ls + n_opt * Vector3::UNIT_Z);

                // set up a transformation matrix to transform the light space to its new origin
                Matrix4 lightSpaceTranslation(Matrix4::IDENTITY);
                lightSpaceTranslation.setTrans(-C);

                // range from bMin to bMax; d = |B_z_far - B_z_near|
                Real d = Math::Abs(bodyBAAB_ls.getMaximum().z - bodyBAAB_ls.getMinimum().z);

                // set up the LiSPSM perspective transformation
                // build up frustum to map P onto the unit cube with (-1/-1/-1) and (+1/+1/+1)
                Matrix4 P = buildFrustumProjection(-1, 1, -1, 1, n_opt, n_opt + d);

                return P * lightSpaceTranslation;
        }
        //-----------------------------------------------------------------------
        Real LiSPSMShadowCameraSetup::calculateNOpt(const Matrix4& lightSpace, 
                const AxisAlignedBox& bodyBABB_ls, const PointListBody& bodyLVS, 
                const Camera& cam) const
        {
                // get inverse light space matrix
                Matrix4 invLightSpace = lightSpace.inverse();

                // get view matrix
                const Matrix4& viewMatrix = cam.getViewMatrix();

                // calculate z0_ls
                const Vector3 e_ws  = getNearCameraPoint_ws(viewMatrix, bodyLVS);
                const Vector3 z0_ls = calculateZ0_ls(lightSpace, e_ws, bodyBABB_ls.getMaximum().z, cam);

                // z1_ls has the same x and y values as z0_ls and the minimum z values of bodyABB_ls
                const Vector3 z1_ls = Vector3(z0_ls.x, z0_ls.y, bodyBABB_ls.getMinimum().z);

                // world
                const Vector3 z0_ws = invLightSpace * z0_ls;
                const Vector3 z1_ws = invLightSpace * z1_ls;

                // eye
                const Vector3 z0_es = viewMatrix * z0_ws;
                const Vector3 z1_es = viewMatrix * z1_ws;

                const Real z0 = z0_es.z;
                const Real z1 = z1_es.z;

                // check if we have to do uniform shadow mapping
                if ((z0 < 0 && z1 > 0) ||
                        (z1 < 0 && z0 > 0))
                {
                        // apply uniform shadow mapping
                        return 0.0;
                }
                return cam.getNearClipDistance() + Math::Sqrt(z0 * z1) * mOptAdjustFactor;
        }
        //-----------------------------------------------------------------------
        Real LiSPSMShadowCameraSetup::calculateNOptSimple(const PointListBody& bodyLVS, 
                const Camera& cam) const
        {
                // get view matrix
                const Matrix4& viewMatrix = cam.getViewMatrix();

                // calculate e_es
                const Vector3 e_ws  = getNearCameraPoint_ws(viewMatrix, bodyLVS);
                const Vector3 e_es = viewMatrix * e_ws;

                // according to the new formula (mainly for directional lights)
                // n_opt = zn + sqrt(z0 * z1);
                // zn is set to Abs(near eye point)
                // z0 is set to the near camera clip distance
                // z1 is set to the far camera clip distance
                return (Math::Abs(e_es.z) + Math::Sqrt(cam.getNearClipDistance() * cam.getFarClipDistance())) * mOptAdjustFactor;
        }
        //-----------------------------------------------------------------------
        Vector3 LiSPSMShadowCameraSetup::calculateZ0_ls(const Matrix4& lightSpace, 
                const Vector3& e, Real bodyB_zMax_ls, const Camera& cam) const
        {
                // z0_ls lies on the intersection point between the planes 'bodyB_ls near plane 
                // (z = bodyB_zNear_ls)' and plane with normal UNIT_X where e_ls lies upon (x = e_ls_x) 
                // and the camera's near clipping plane (ls). We are looking towards the negative 
                // z-direction, so bodyB_zNear_ls equals bodyB_zMax_ls.

                const Vector3& camDir = cam.getDerivedDirection();
                const Vector3 e_ls = lightSpace * e;

                // set up a plane with the camera direction as normal and e as a point on the plane
                Plane plane(camDir, e);

                plane = lightSpace * plane;

                // try to intersect plane with a ray from origin V3(e_ls_x, 0.0, bodyB_zNear_ls)T
                // and direction +/- UNIT_Y
                Ray ray(Vector3(e_ls.x, 0.0, bodyB_zMax_ls), Vector3::UNIT_Y);
                std::pair< bool, Real > intersect = ray.intersects(plane);

                // we got an intersection point
                if (intersect.first == true)
                {
                        return ray.getPoint(intersect.second);
                }
                else
                {
                        // try the other direction
                        ray = Ray(Vector3(e_ls.x, 0.0, bodyB_zMax_ls), Vector3::NEGATIVE_UNIT_Y);
                        std::pair< bool, Real > intersect = ray.intersects(plane);

                        // we got an intersection point
                        if (intersect.first == true)
                        {
                                return ray.getPoint(intersect.second);
                        }
                        else
                        {
                                // failure!
                                return Vector3(0.0, 0.0, 0.0);
                        }
                }
        }
        //-----------------------------------------------------------------------
        Matrix4 LiSPSMShadowCameraSetup::buildFrustumProjection(Real left, Real right, 
                Real bottom, Real top, Real near, Real far) const
        {
                Real m00 = 2 * near / (right - left),
                        m02 = (right + left) / (right - left),
                        m11 = 2 * near / (top - bottom),
                        m12 = (top + bottom) / (top - bottom),
                        m22 = -(far + near) / (far - near),
                        m23 = -2 * far * near / (far - near),
                        m32 = -1;

                Matrix4 m(m00, 0.0, m02, 0.0,
                        0.0, m11, m12, 0.0,
                        0.0, 0.0, m22, m23,
                        0.0, 0.0, m32, 0.0);

                return m;
        }
        //-----------------------------------------------------------------------
        void LiSPSMShadowCameraSetup::getShadowCamera (const SceneManager *sm, const Camera *cam, 
                const Viewport *vp, const Light *light, Camera *texCam) const
        {
                // check availability - viewport not needed
                OgreAssert(sm != NULL, "SceneManager is NULL");
                OgreAssert(cam != NULL, "Camera (viewer) is NULL");
                OgreAssert(light != NULL, "Light is NULL");
                OgreAssert(texCam != NULL, "Camera (texture) is NULL");
                mLightFrustumCameraCalculated = false;


                // calculate standard shadow mapping matrix
                Matrix4 LView, LProj;
                calculateShadowMappingMatrix(*sm, *cam, *light, &LView, &LProj, NULL);

                // build scene bounding box
                const VisibleObjectsBoundsInfo& visInfo = sm->getShadowCasterBoundsInfo(light);
                AxisAlignedBox sceneBB = visInfo.aabb;
                sceneBB.merge(sm->getVisibleObjectsBoundsInfo(cam).aabb);
                sceneBB.merge(cam->getDerivedPosition());

                // in case the sceneBB is empty (e.g. nothing visible to the cam) simply
                // return the standard shadow mapping matrix
                if (sceneBB.isNull())
                {
                        texCam->setCustomViewMatrix(true, LView);
                        texCam->setCustomProjectionMatrix(true, LProj);
                        return;
                }

                // calculate the intersection body B
                mPointListBodyB.reset();
                calculateB(*sm, *cam, *light, sceneBB, &mPointListBodyB);

                // in case the bodyB is empty (e.g. nothing visible to the light or the cam)
                // simply return the standard shadow mapping matrix
                if (mPointListBodyB.getPointCount() == 0)
                {
                        texCam->setCustomViewMatrix(true, LView);
                        texCam->setCustomProjectionMatrix(true, LProj);
                        return;
                }

                // transform to light space: y -> -z, z -> y
                LProj = msNormalToLightSpace * LProj;

                // calculate LVS so it does not need to be calculated twice
                // calculate the body L \cap V \cap S to make sure all returned points are in 
                // front of the camera
                calculateLVS(*sm, *cam, *light, sceneBB, &mPointListBodyLVS);

                // fetch the viewing direction
                const Vector3 viewDir = getLSProjViewDir(LProj * LView, *cam, mPointListBodyLVS);

                // The light space will be rotated in such a way, that the projected light view 
                // always points upwards, so the up-vector is the y-axis (we already prepared the
                // light space for this usage).The transformation matrix is set up with the
                // following parameters:
                // - position is the origin
                // - the view direction is the calculated viewDir
                // - the up vector is the y-axis
                LProj = buildViewMatrix(Vector3::ZERO, viewDir, Vector3::UNIT_Y) * LProj;

                // calculate LiSPSM projection
                LProj = calculateLiSPSM(LProj * LView, mPointListBodyB, mPointListBodyLVS, *sm, *cam, *light) * LProj;

                // map bodyB to unit cube
                LProj = transformToUnitCube(LProj * LView, mPointListBodyB) * LProj;

                // transform from light space to normal space: y -> z, z -> -y
                LProj = msLightSpaceToNormal * LProj;

                // LView = Lv^-1
                // LProj = Switch_{-ls} * FocusBody * P * L_r * Switch_{ls} * L_p
                texCam->setCustomViewMatrix(true, LView);
                texCam->setCustomProjectionMatrix(true, LProj);
        }

}