openmw/components/stereo/frustum.cpp

#include "multiview.hpp"

#include <osg/DisplaySettings>
#include <osg/Texture2D>
#include <osg/Texture2DArray>
#include <osg/Texture2DMultisample>
#include <osg/io_utils>

#include <osgUtil/CullVisitor>
#include <osgUtil/RenderStage>

#include <osgViewer/Renderer>
#include <osgViewer/Viewer>

#include <map>
#include <string>

#include <components/sceneutil/color.hpp>
#include <components/sceneutil/mwshadowtechnique.hpp>

#include <components/settings/settings.hpp>

#include "frustum.hpp"

namespace Stereo
{
    struct MultiviewFrustumCallback final : public Stereo::InitialFrustumCallback
    {
        MultiviewFrustumCallback(StereoFrustumManager* sfm, osg::Camera* camera)
            : Stereo::InitialFrustumCallback(camera)
            , mSfm(sfm)
        {
        }

        void setInitialFrustum(
            osg::CullStack& cullStack, osg::BoundingBoxd& bb, bool& nearCulling, bool& farCulling) const override
        {
            auto cm = cullStack.getCullingMode();
            nearCulling = !!(cm & osg::CullSettings::NEAR_PLANE_CULLING);
            farCulling = !!(cm & osg::CullSettings::FAR_PLANE_CULLING);
            bb = mSfm->boundingBox();
        }

        StereoFrustumManager* mSfm;
    };

    struct ShadowFrustumCallback final : public SceneUtil::MWShadowTechnique::CustomFrustumCallback
    {
        ShadowFrustumCallback(StereoFrustumManager* parent)
            : mParent(parent)
        {
        }

        void operator()(osgUtil::CullVisitor& cv, osg::BoundingBoxd& customClipSpace,
            osgUtil::CullVisitor*& sharedFrustumHint) override
        {
            mParent->customFrustumCallback(cv, customClipSpace, sharedFrustumHint);
        }

        StereoFrustumManager* mParent;
    };

    void joinBoundingBoxes(
        const osg::Matrix& masterProjection, const osg::Matrix& slaveProjection, osg::BoundingBoxd& bb)
    {
        static const std::array<osg::Vec3d, 8> clipCorners = { {
            { -1.0, -1.0, -1.0 },
            { 1.0, -1.0, -1.0 },
            { 1.0, -1.0, 1.0 },
            { -1.0, -1.0, 1.0 },
            { -1.0, 1.0, -1.0 },
            { 1.0, 1.0, -1.0 },
            { 1.0, 1.0, 1.0 },
            { -1.0, 1.0, 1.0 },
        } };

        osg::Matrix slaveClipToView;
        slaveClipToView.invert(slaveProjection);

        for (const auto& clipCorner : clipCorners)
        {
            auto masterViewVertice = clipCorner * slaveClipToView;
            auto masterClipVertice = masterViewVertice * masterProjection;
            bb.expandBy(masterClipVertice);
        }
    }

    StereoFrustumManager::StereoFrustumManager(bool sharedShadowMaps, osg::Camera* camera)
        : mCamera(camera)
        , mShadowTechnique(nullptr)
        , mShadowFrustumCallback(nullptr)
    {
        if (Stereo::getMultiview())
        {
            mMultiviewFrustumCallback = std::make_unique<MultiviewFrustumCallback>(this, camera);
        }

        if (sharedShadowMaps)
        {
            mShadowFrustumCallback = new ShadowFrustumCallback(this);
            auto* renderer = static_cast<osgViewer::Renderer*>(mCamera->getRenderer());
            for (auto* sceneView : { renderer->getSceneView(0), renderer->getSceneView(1) })
            {
                mSharedFrustums[sceneView->getCullVisitorRight()] = sceneView->getCullVisitorLeft();
            }
        }
    }

    StereoFrustumManager::~StereoFrustumManager()
    {
        if (mShadowTechnique)
            mShadowTechnique->setCustomFrustumCallback(nullptr);
    }

    void StereoFrustumManager::setShadowTechnique(SceneUtil::MWShadowTechnique* shadowTechnique)
    {
        if (mShadowTechnique)
            mShadowTechnique->setCustomFrustumCallback(nullptr);
        mShadowTechnique = shadowTechnique;
        if (mShadowTechnique)
            mShadowTechnique->setCustomFrustumCallback(mShadowFrustumCallback);
    }

    void StereoFrustumManager::customFrustumCallback(
        osgUtil::CullVisitor& cv, osg::BoundingBoxd& customClipSpace, osgUtil::CullVisitor*& sharedFrustumHint)
    {
        auto it = mSharedFrustums.find(&cv);
        if (it != mSharedFrustums.end())
        {
            sharedFrustumHint = it->second;
        }

        customClipSpace = mBoundingBox;
    }

    void StereoFrustumManager::update(std::array<osg::Matrix, 2> projections)
    {
        mBoundingBox.init();
        for (auto& projection : projections)
            joinBoundingBoxes(mCamera->getProjectionMatrix(), projection, mBoundingBox);
    }
}