openmw/components/stereo/multiview.cpp

#include "multiview.hpp"

#include <osg/FrameBufferObject>
#include <osg/GLExtensions>
#include <osg/Texture2D>
#include <osg/Texture2DArray>
#include <osg/Texture2DMultisample>
#include <osgUtil/CullVisitor>
#include <osgUtil/RenderStage>

#ifdef OSG_HAS_MULTIVIEW
#include <osg/Texture2DMultisampleArray>
#endif

#include <components/debug/debuglog.hpp>
#include <components/sceneutil/nodecallback.hpp>
#include <components/settings/settings.hpp>
#include <components/stereo/stereomanager.hpp>

#include <algorithm>

namespace Stereo
{
    namespace
    {
        bool getMultiviewSupportedImpl(unsigned int contextID)
        {
#ifdef OSG_HAS_MULTIVIEW
            if (!osg::isGLExtensionSupported(contextID, "GL_OVR_multiview"))
            {
                Log(Debug::Verbose) << "Disabling Multiview (opengl extension \"GL_OVR_multiview\" not supported)";
                return false;
            }

            if (!osg::isGLExtensionSupported(contextID, "GL_OVR_multiview2"))
            {
                Log(Debug::Verbose) << "Disabling Multiview (opengl extension \"GL_OVR_multiview2\" not supported)";
                return false;
            }
            return true;
#else
            Log(Debug::Verbose) << "Disabling Multiview (OSG does not support multiview)";
            return false;
#endif
        }

        bool getMultiviewSupported(unsigned int contextID)
        {
            static bool supported = getMultiviewSupportedImpl(contextID);
            return supported;
        }

        bool getTextureViewSupportedImpl(unsigned int contextID)
        {
            if (!osg::isGLExtensionOrVersionSupported(contextID, "ARB_texture_view", 4.3))
            {
                Log(Debug::Verbose) << "Disabling texture views (opengl extension \"ARB_texture_view\" not supported)";
                return false;
            }
            return true;
        }

        bool getTextureViewSupported(unsigned int contextID)
        {
            static bool supported = getTextureViewSupportedImpl(contextID);
            return supported;
        }

        bool getMultiviewImpl(unsigned int contextID)
        {
            if (!Stereo::getStereo())
            {
                Log(Debug::Verbose) << "Disabling Multiview (disabled by config)";
                return false;
            }

            if (!getMultiviewSupported(contextID))
            {
                return false;
            }

            if (!getTextureViewSupported(contextID))
            {
                Log(Debug::Verbose) << "Disabling Multiview (texture views not supported)";
                return false;
            }

            Log(Debug::Verbose) << "Enabling Multiview";
            return true;
        }

        static bool sMultiview = false;

        bool getMultiview(unsigned int contextID)
        {
            static bool multiView = getMultiviewImpl(contextID);
            return multiView;
        }
    }

    bool getTextureViewSupported()
    {
        return getTextureViewSupported(0);
    }

    bool getMultiview()
    {
        return getMultiview(0);
    }

    void configureExtensions(unsigned int contextID, bool enableMultiview)
    {
        getTextureViewSupported(contextID);
        getMultiviewSupported(contextID);

        if (enableMultiview)
        {
            sMultiview = getMultiview(contextID);
        }
        else
        {
            Log(Debug::Verbose) << "Disabling Multiview (disabled by config)";
            sMultiview = false;
        }
    }

    void setVertexBufferHint(bool enableMultiview)
    {
        if (getStereo() && enableMultiview)
        {
            auto* ds = osg::DisplaySettings::instance().get();
            if (!Settings::Manager::getBool("allow display lists for multiview", "Stereo")
                && ds->getVertexBufferHint() == osg::DisplaySettings::VertexBufferHint::NO_PREFERENCE)
            {
                // Note that this only works if this code is executed before realize() is called on the viewer.
                // The hint is read by the state object only once, before the user realize operations are run.
                // Therefore we have to set this hint without access to a graphics context to let us determine
                // if multiview will actually be supported or not. So if the user has requested multiview, we
                // will just have to set it regardless.
                ds->setVertexBufferHint(osg::DisplaySettings::VertexBufferHint::VERTEX_BUFFER_OBJECT);
                Log(Debug::Verbose) << "Disabling display lists";
            }
        }
    }

    class Texture2DViewSubloadCallback : public osg::Texture2D::SubloadCallback
    {
    public:
        Texture2DViewSubloadCallback(osg::Texture2DArray* textureArray, int layer);

        void load(const osg::Texture2D& texture, osg::State& state) const override;
        void subload(const osg::Texture2D& texture, osg::State& state) const override;

    private:
        osg::ref_ptr<osg::Texture2DArray> mTextureArray;
        int mLayer;
    };

    Texture2DViewSubloadCallback::Texture2DViewSubloadCallback(osg::Texture2DArray* textureArray, int layer)
        : mTextureArray(textureArray)
        , mLayer(layer)
    {
    }

    void Texture2DViewSubloadCallback::load(const osg::Texture2D& texture, osg::State& state) const
    {
        state.checkGLErrors("before Texture2DViewSubloadCallback::load()");

        auto contextId = state.getContextID();
        auto* gl = osg::GLExtensions::Get(contextId, false);
        mTextureArray->apply(state);

        auto sourceTextureObject = mTextureArray->getTextureObject(contextId);
        if (!sourceTextureObject)
        {
            Log(Debug::Error) << "Texture2DViewSubloadCallback: Texture2DArray did not have a texture object";
            return;
        }

        osg::Texture::TextureObject* const targetTextureObject = texture.getTextureObject(contextId);
        if (targetTextureObject == nullptr)
        {
            Log(Debug::Error) << "Texture2DViewSubloadCallback: Texture2D did not have a texture object";
            return;
        }

        // OSG already bound this texture ID, giving it a target.
        // Delete it and make a new texture ID.
        glBindTexture(GL_TEXTURE_2D, 0);
        glDeleteTextures(1, &targetTextureObject->_id);
        glGenTextures(1, &targetTextureObject->_id);

        auto sourceId = sourceTextureObject->_id;
        auto targetId = targetTextureObject->_id;
        auto internalFormat = sourceTextureObject->_profile._internalFormat;
        auto levels = std::max(1, sourceTextureObject->_profile._numMipmapLevels);

        {
            ////// OSG BUG
            // Texture views require immutable storage.
            // OSG should always give immutable storage to sized internal formats, but does not do so for depth formats.
            // Fortunately, we can just call glTexStorage3D here to make it immutable. This probably discards depth info
            // for that frame, but whatever.
#ifndef GL_TEXTURE_IMMUTABLE_FORMAT
#define GL_TEXTURE_IMMUTABLE_FORMAT 0x912F
#endif
            // Store any current binding and re-apply it after so i don't mess with state.
            GLint oldBinding = 0;
            glGetIntegerv(GL_TEXTURE_BINDING_2D_ARRAY, &oldBinding);

            // Bind the source texture and check if it's immutable.
            glBindTexture(GL_TEXTURE_2D_ARRAY, sourceId);
            GLint immutable = 0;
            glGetTexParameteriv(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_IMMUTABLE_FORMAT, &immutable);
            if (!immutable)
            {
                // It wasn't immutable, so make it immutable.
                gl->glTexStorage3D(GL_TEXTURE_2D_ARRAY, 1, internalFormat, sourceTextureObject->_profile._width,
                    sourceTextureObject->_profile._height, 2);
                state.checkGLErrors("after Texture2DViewSubloadCallback::load()::glTexStorage3D");
            }
            glBindTexture(GL_TEXTURE_2D_ARRAY, oldBinding);
        }

        gl->glTextureView(targetId, GL_TEXTURE_2D, sourceId, internalFormat, 0, levels, mLayer, 1);
        state.checkGLErrors("after Texture2DViewSubloadCallback::load()::glTextureView");
        glBindTexture(GL_TEXTURE_2D, targetId);
    }

    void Texture2DViewSubloadCallback::subload(const osg::Texture2D& texture, osg::State& state) const
    {
        // Nothing to do
    }

    osg::ref_ptr<osg::Texture2D> createTextureView_Texture2DFromTexture2DArray(
        osg::Texture2DArray* textureArray, int layer)
    {
        if (!getTextureViewSupported())
        {
            Log(Debug::Error) << "createTextureView_Texture2DFromTexture2DArray: Tried to use a texture view but "
                                 "glTextureView is not supported";
            return nullptr;
        }

        osg::ref_ptr<osg::Texture2D> texture2d = new osg::Texture2D;
        texture2d->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
        texture2d->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
        texture2d->setSubloadCallback(new Texture2DViewSubloadCallback(textureArray, layer));
        texture2d->setTextureSize(textureArray->getTextureWidth(), textureArray->getTextureHeight());
        texture2d->setBorderColor(textureArray->getBorderColor());
        texture2d->setBorderWidth(textureArray->getBorderWidth());
        texture2d->setLODBias(textureArray->getLODBias());
        texture2d->setFilter(osg::Texture::FilterParameter::MAG_FILTER,
            textureArray->getFilter(osg::Texture::FilterParameter::MAG_FILTER));
        texture2d->setFilter(osg::Texture::FilterParameter::MIN_FILTER,
            textureArray->getFilter(osg::Texture::FilterParameter::MIN_FILTER));
        texture2d->setInternalFormat(textureArray->getInternalFormat());
        texture2d->setNumMipmapLevels(textureArray->getNumMipmapLevels());
        return texture2d;
    }

#ifdef OSG_HAS_MULTIVIEW
    //! Draw callback that, if set on a RenderStage, resolves MSAA after draw. Needed when using custom fbo/resolve fbos
    //! on renderstages in combination with multiview.
    struct MultiviewMSAAResolveCallback : public osgUtil::RenderBin::DrawCallback
    {
        void drawImplementation(
            osgUtil::RenderBin* bin, osg::RenderInfo& renderInfo, osgUtil::RenderLeaf*& previous) override
        {
            osgUtil::RenderStage* stage = static_cast<osgUtil::RenderStage*>(bin);
            auto msaaFbo = stage->getFrameBufferObject();
            auto resolveFbo = stage->getMultisampleResolveFramebufferObject();
            if (msaaFbo != mMsaaFbo)
            {
                mMsaaFbo = msaaFbo;
                setupMsaaLayers();
            }
            if (resolveFbo != mFbo)
            {
                mFbo = resolveFbo;
                setupLayers();
            }

            // Null the resolve framebuffer to keep osg from doing redundant work.
            stage->setMultisampleResolveFramebufferObject(nullptr);

            // Do the actual render work
            bin->drawImplementation(renderInfo, previous);

            // Blit layers
            osg::State& state = *renderInfo.getState();
            osg::GLExtensions* ext = state.get<osg::GLExtensions>();
            for (int i = 0; i < 2; i++)
            {
                mLayers[i]->apply(state, osg::FrameBufferObject::DRAW_FRAMEBUFFER);
                mMsaaLayers[i]->apply(state, osg::FrameBufferObject::READ_FRAMEBUFFER);
                ext->glBlitFramebuffer(0, 0, mWidth, mHeight, 0, 0, mWidth, mHeight,
                    GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT, GL_NEAREST);
            }
            msaaFbo->apply(state, osg::FrameBufferObject::READ_DRAW_FRAMEBUFFER);
        }

        void setupLayers()
        {
            const auto& attachments = mFbo->getAttachmentMap();
            for (int i = 0; i < 2; i++)
            {
                mLayers[i] = new osg::FrameBufferObject;
                // Intentionally not using ref& so attachment can be non-const
                for (auto [component, attachment] : attachments)
                {
                    osg::Texture2DArray* texture = static_cast<osg::Texture2DArray*>(attachment.getTexture());
                    mLayers[i]->setAttachment(component, osg::FrameBufferAttachment(texture, i));
                    mWidth = texture->getTextureWidth();
                    mHeight = texture->getTextureHeight();
                }
            }
        }

        void setupMsaaLayers()
        {
            const auto& attachments = mMsaaFbo->getAttachmentMap();
            for (int i = 0; i < 2; i++)
            {
                mMsaaLayers[i] = new osg::FrameBufferObject;
                // Intentionally not using ref& so attachment can be non-const
                for (auto [component, attachment] : attachments)
                {
                    osg::Texture2DMultisampleArray* texture
                        = static_cast<osg::Texture2DMultisampleArray*>(attachment.getTexture());
                    mMsaaLayers[i]->setAttachment(component, osg::FrameBufferAttachment(texture, i));
                    mWidth = texture->getTextureWidth();
                    mHeight = texture->getTextureHeight();
                }
            }
        }

        osg::ref_ptr<osg::FrameBufferObject> mFbo;
        osg::ref_ptr<osg::FrameBufferObject> mMsaaFbo;
        osg::ref_ptr<osg::FrameBufferObject> mLayers[2];
        osg::ref_ptr<osg::FrameBufferObject> mMsaaLayers[2];
        int mWidth;
        int mHeight;
    };
#endif

    void setMultiviewMSAAResolveCallback(osgUtil::RenderStage* renderStage)
    {
#ifdef OSG_HAS_MULTIVIEW
        if (Stereo::getMultiview())
        {
            renderStage->setDrawCallback(new MultiviewMSAAResolveCallback);
        }
#endif
    }

    void setMultiviewMatrices(
        osg::StateSet* stateset, const std::array<osg::Matrix, 2>& projection, bool createInverseMatrices)
    {
        auto* projUniform = stateset->getUniform("projectionMatrixMultiView");
        if (!projUniform)
        {
            projUniform = new osg::Uniform(osg::Uniform::FLOAT_MAT4, "projectionMatrixMultiView", 2);
            stateset->addUniform(projUniform, osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
        }

        projUniform->setElement(0, projection[0]);
        projUniform->setElement(1, projection[1]);

        if (createInverseMatrices)
        {
            auto* invUniform = stateset->getUniform("invProjectionMatrixMultiView");
            if (!invUniform)
            {
                invUniform = new osg::Uniform(osg::Uniform::FLOAT_MAT4, "invProjectionMatrixMultiView", 2);
                stateset->addUniform(invUniform, osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
            }

            invUniform->setElement(0, osg::Matrix::inverse(projection[0]));
            invUniform->setElement(1, osg::Matrix::inverse(projection[1]));
        }
    }

    void setMultiviewCompatibleTextureSize(osg::Texture* tex, int w, int h)
    {
        switch (tex->getTextureTarget())
        {
            case GL_TEXTURE_2D:
                static_cast<osg::Texture2D*>(tex)->setTextureSize(w, h);
                break;
            case GL_TEXTURE_2D_ARRAY:
                static_cast<osg::Texture2DArray*>(tex)->setTextureSize(w, h, 2);
                break;
            case GL_TEXTURE_2D_MULTISAMPLE:
                static_cast<osg::Texture2DMultisample*>(tex)->setTextureSize(w, h);
                break;
#ifdef OSG_HAS_MULTIVIEW
            case GL_TEXTURE_2D_MULTISAMPLE_ARRAY:
                static_cast<osg::Texture2DMultisampleArray*>(tex)->setTextureSize(w, h, 2);
                break;
#endif
            default:
                throw std::logic_error("Invalid texture type received");
        }
    }

    osg::ref_ptr<osg::Texture> createMultiviewCompatibleTexture(int width, int height, int samples)
    {
#ifdef OSG_HAS_MULTIVIEW
        if (Stereo::getMultiview())
        {
            if (samples > 1)
            {
                auto tex = new osg::Texture2DMultisampleArray();
                tex->setTextureSize(width, height, 2);
                tex->setNumSamples(samples);
                return tex;
            }
            else
            {
                auto tex = new osg::Texture2DArray();
                tex->setTextureSize(width, height, 2);
                return tex;
            }
        }
        else
#endif
        {
            if (samples > 1)
            {
                auto tex = new osg::Texture2DMultisample();
                tex->setTextureSize(width, height);
                tex->setNumSamples(samples);
                tex->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
                tex->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
                return tex;
            }
            else
            {
                auto tex = new osg::Texture2D();
                tex->setTextureSize(width, height);
                tex->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
                tex->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
                return tex;
            }
        }
    }

    osg::FrameBufferAttachment createMultiviewCompatibleAttachment(osg::Texture* tex)
    {
        switch (tex->getTextureTarget())
        {
            case GL_TEXTURE_2D:
            {
                auto* tex2d = static_cast<osg::Texture2D*>(tex);
                return osg::FrameBufferAttachment(tex2d);
            }
            case GL_TEXTURE_2D_MULTISAMPLE:
            {
                auto* tex2dMsaa = static_cast<osg::Texture2DMultisample*>(tex);
                return osg::FrameBufferAttachment(tex2dMsaa);
            }
#ifdef OSG_HAS_MULTIVIEW
            case GL_TEXTURE_2D_ARRAY:
            {
                auto* tex2dArray = static_cast<osg::Texture2DArray*>(tex);
                return osg::FrameBufferAttachment(tex2dArray, osg::Camera::FACE_CONTROLLED_BY_MULTIVIEW_SHADER, 0);
            }
            case GL_TEXTURE_2D_MULTISAMPLE_ARRAY:
            {
                auto* tex2dMsaaArray = static_cast<osg::Texture2DMultisampleArray*>(tex);
                return osg::FrameBufferAttachment(tex2dMsaaArray, osg::Camera::FACE_CONTROLLED_BY_MULTIVIEW_SHADER, 0);
            }
#endif
            default:
                throw std::logic_error("Invalid texture type received");
        }
    }

    unsigned int osgFaceControlledByMultiviewShader()
    {
#ifdef OSG_HAS_MULTIVIEW
        return osg::Camera::FACE_CONTROLLED_BY_MULTIVIEW_SHADER;
#else
        return 0;
#endif
    }

    class UpdateRenderStagesCallback
        : public SceneUtil::NodeCallback<UpdateRenderStagesCallback, osg::Node*, osgUtil::CullVisitor*>
    {
    public:
        UpdateRenderStagesCallback(Stereo::MultiviewFramebuffer* multiviewFramebuffer)
            : mMultiviewFramebuffer(multiviewFramebuffer)
        {
            mViewport = new osg::Viewport(0, 0, multiviewFramebuffer->width(), multiviewFramebuffer->height());
            mViewportStateset = new osg::StateSet();
            mViewportStateset->setAttribute(mViewport.get());
        }

        void operator()(osg::Node* node, osgUtil::CullVisitor* cv)
        {
            osgUtil::RenderStage* renderStage = cv->getCurrentRenderStage();

            bool msaa = mMultiviewFramebuffer->samples() > 1;

            if (!Stereo::getMultiview())
            {
                auto eye = static_cast<int>(Stereo::Manager::instance().getEye(cv));

                if (msaa)
                {
                    renderStage->setFrameBufferObject(mMultiviewFramebuffer->layerMsaaFbo(eye));
                    renderStage->setMultisampleResolveFramebufferObject(mMultiviewFramebuffer->layerFbo(eye));
                }
                else
                {
                    renderStage->setFrameBufferObject(mMultiviewFramebuffer->layerFbo(eye));
                }
            }

            // OSG tries to do a horizontal split, but we want to render to separate framebuffers instead.
            renderStage->setViewport(mViewport);
            cv->pushStateSet(mViewportStateset.get());
            traverse(node, cv);
            cv->popStateSet();
        }

    private:
        Stereo::MultiviewFramebuffer* mMultiviewFramebuffer;
        osg::ref_ptr<osg::Viewport> mViewport;
        osg::ref_ptr<osg::StateSet> mViewportStateset;
    };

    MultiviewFramebuffer::MultiviewFramebuffer(int width, int height, int samples)
        : mWidth(width)
        , mHeight(height)
        , mSamples(samples)
        , mMultiview(getMultiview())
        , mMultiviewFbo{ new osg::FrameBufferObject }
        , mLayerFbo{ new osg::FrameBufferObject, new osg::FrameBufferObject }
        , mLayerMsaaFbo{ new osg::FrameBufferObject, new osg::FrameBufferObject }
    {
    }

    MultiviewFramebuffer::~MultiviewFramebuffer() {}

    void MultiviewFramebuffer::attachColorComponent(GLint sourceFormat, GLint sourceType, GLint internalFormat)
    {
        if (mMultiview)
        {
#ifdef OSG_HAS_MULTIVIEW
            mMultiviewColorTexture = createTextureArray(sourceFormat, sourceType, internalFormat);
            mMultiviewFbo->setAttachment(osg::Camera::COLOR_BUFFER,
                osg::FrameBufferAttachment(
                    mMultiviewColorTexture, osg::Camera::FACE_CONTROLLED_BY_MULTIVIEW_SHADER, 0));
            for (unsigned i = 0; i < 2; i++)
            {
                mColorTexture[i] = createTextureView_Texture2DFromTexture2DArray(mMultiviewColorTexture.get(), i);
                mLayerFbo[i]->setAttachment(osg::Camera::COLOR_BUFFER, osg::FrameBufferAttachment(mColorTexture[i]));
            }
#endif
        }
        else
        {
            for (unsigned i = 0; i < 2; i++)
            {
                if (mSamples > 1)
                    mLayerMsaaFbo[i]->setAttachment(osg::Camera::COLOR_BUFFER,
                        osg::FrameBufferAttachment(new osg::RenderBuffer(mWidth, mHeight, internalFormat, mSamples)));
                mColorTexture[i] = createTexture(sourceFormat, sourceType, internalFormat);
                mLayerFbo[i]->setAttachment(osg::Camera::COLOR_BUFFER, osg::FrameBufferAttachment(mColorTexture[i]));
            }
        }
    }

    void MultiviewFramebuffer::attachDepthComponent(GLint sourceFormat, GLint sourceType, GLint internalFormat)
    {
        if (mMultiview)
        {
#ifdef OSG_HAS_MULTIVIEW
            mMultiviewDepthTexture = createTextureArray(sourceFormat, sourceType, internalFormat);
            mMultiviewFbo->setAttachment(osg::Camera::PACKED_DEPTH_STENCIL_BUFFER,
                osg::FrameBufferAttachment(
                    mMultiviewDepthTexture, osg::Camera::FACE_CONTROLLED_BY_MULTIVIEW_SHADER, 0));
            for (unsigned i = 0; i < 2; i++)
            {
                mDepthTexture[i] = createTextureView_Texture2DFromTexture2DArray(mMultiviewDepthTexture.get(), i);
                mLayerFbo[i]->setAttachment(
                    osg::Camera::PACKED_DEPTH_STENCIL_BUFFER, osg::FrameBufferAttachment(mDepthTexture[i]));
            }
#endif
        }
        else
        {
            for (unsigned i = 0; i < 2; i++)
            {
                if (mSamples > 1)
                    mLayerMsaaFbo[i]->setAttachment(osg::Camera::PACKED_DEPTH_STENCIL_BUFFER,
                        osg::FrameBufferAttachment(new osg::RenderBuffer(mWidth, mHeight, internalFormat, mSamples)));
                mDepthTexture[i] = createTexture(sourceFormat, sourceType, internalFormat);
                mLayerFbo[i]->setAttachment(
                    osg::Camera::PACKED_DEPTH_STENCIL_BUFFER, osg::FrameBufferAttachment(mDepthTexture[i]));
            }
        }
    }

    osg::FrameBufferObject* MultiviewFramebuffer::multiviewFbo()
    {
        return mMultiviewFbo;
    }

    osg::FrameBufferObject* MultiviewFramebuffer::layerFbo(int i)
    {
        return mLayerFbo[i];
    }

    osg::FrameBufferObject* MultiviewFramebuffer::layerMsaaFbo(int i)
    {
        return mLayerMsaaFbo[i];
    }

    osg::Texture2DArray* MultiviewFramebuffer::multiviewColorBuffer()
    {
        return mMultiviewColorTexture;
    }

    osg::Texture2DArray* MultiviewFramebuffer::multiviewDepthBuffer()
    {
        return mMultiviewDepthTexture;
    }

    osg::Texture2D* MultiviewFramebuffer::layerColorBuffer(int i)
    {
        return mColorTexture[i];
    }

    osg::Texture2D* MultiviewFramebuffer::layerDepthBuffer(int i)
    {
        return mDepthTexture[i];
    }
    void MultiviewFramebuffer::attachTo(osg::Camera* camera)
    {
#ifdef OSG_HAS_MULTIVIEW
        if (mMultiview)
        {
            if (mMultiviewColorTexture)
            {
                camera->attach(osg::Camera::COLOR_BUFFER, mMultiviewColorTexture, 0,
                    osg::Camera::FACE_CONTROLLED_BY_MULTIVIEW_SHADER, false, mSamples);
                camera->getBufferAttachmentMap()[osg::Camera::COLOR_BUFFER]._internalFormat
                    = mMultiviewColorTexture->getInternalFormat();
                camera->getBufferAttachmentMap()[osg::Camera::COLOR_BUFFER]._mipMapGeneration = false;
            }
            if (mMultiviewDepthTexture)
            {
                camera->attach(osg::Camera::PACKED_DEPTH_STENCIL_BUFFER, mMultiviewDepthTexture, 0,
                    osg::Camera::FACE_CONTROLLED_BY_MULTIVIEW_SHADER, false, mSamples);
                camera->getBufferAttachmentMap()[osg::Camera::PACKED_DEPTH_STENCIL_BUFFER]._internalFormat
                    = mMultiviewDepthTexture->getInternalFormat();
                camera->getBufferAttachmentMap()[osg::Camera::PACKED_DEPTH_STENCIL_BUFFER]._mipMapGeneration = false;
            }
        }
#endif
        camera->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);

        if (!mCullCallback)
            mCullCallback = new UpdateRenderStagesCallback(this);
        camera->addCullCallback(mCullCallback);
    }

    void MultiviewFramebuffer::detachFrom(osg::Camera* camera)
    {
#ifdef OSG_HAS_MULTIVIEW
        if (mMultiview)
        {
            if (mMultiviewColorTexture)
            {
                camera->detach(osg::Camera::COLOR_BUFFER);
            }
            if (mMultiviewDepthTexture)
            {
                camera->detach(osg::Camera::PACKED_DEPTH_STENCIL_BUFFER);
            }
        }
#endif
        camera->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER);
        if (mCullCallback)
            camera->removeCullCallback(mCullCallback);
    }

    osg::Texture2D* MultiviewFramebuffer::createTexture(GLint sourceFormat, GLint sourceType, GLint internalFormat)
    {
        osg::Texture2D* texture = new osg::Texture2D;
        texture->setTextureSize(mWidth, mHeight);
        texture->setSourceFormat(sourceFormat);
        texture->setSourceType(sourceType);
        texture->setInternalFormat(internalFormat);
        texture->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);
        texture->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);
        texture->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
        texture->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
        texture->setWrap(osg::Texture::WRAP_R, osg::Texture::CLAMP_TO_EDGE);
        return texture;
    }

    osg::Texture2DArray* MultiviewFramebuffer::createTextureArray(
        GLint sourceFormat, GLint sourceType, GLint internalFormat)
    {
        osg::Texture2DArray* textureArray = new osg::Texture2DArray;
        textureArray->setTextureSize(mWidth, mHeight, 2);
        textureArray->setSourceFormat(sourceFormat);
        textureArray->setSourceType(sourceType);
        textureArray->setInternalFormat(internalFormat);
        textureArray->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);
        textureArray->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);
        textureArray->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
        textureArray->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
        textureArray->setWrap(osg::Texture::WRAP_R, osg::Texture::CLAMP_TO_EDGE);
        return textureArray;
    }

    osg::FrameBufferAttachment makeSingleLayerAttachmentFromMultilayerAttachment(
        osg::FrameBufferAttachment attachment, int layer)
    {
        osg::Texture* tex = attachment.getTexture();

        if (tex->getTextureTarget() == GL_TEXTURE_2D_ARRAY)
            return osg::FrameBufferAttachment(static_cast<osg::Texture2DArray*>(tex), layer, 0);

#ifdef OSG_HAS_MULTIVIEW
        if (tex->getTextureTarget() == GL_TEXTURE_2D_MULTISAMPLE_ARRAY)
            return osg::FrameBufferAttachment(static_cast<osg::Texture2DMultisampleArray*>(tex), layer, 0);
#endif

        Log(Debug::Error) << "Attempted to extract a layer from an unlayered texture";

        return osg::FrameBufferAttachment();
    }

    MultiviewFramebufferResolve::MultiviewFramebufferResolve(
        osg::FrameBufferObject* msaaFbo, osg::FrameBufferObject* resolveFbo, GLbitfield blitMask)
        : mResolveFbo(resolveFbo)
        , mMsaaFbo(msaaFbo)
        , mBlitMask(blitMask)
    {
    }

    void MultiviewFramebufferResolve::setResolveFbo(osg::FrameBufferObject* resolveFbo)
    {
        if (resolveFbo != mResolveFbo)
            dirty();
        mResolveFbo = resolveFbo;
    }

    void MultiviewFramebufferResolve::setMsaaFbo(osg::FrameBufferObject* msaaFbo)
    {
        if (msaaFbo != mMsaaFbo)
            dirty();
        mMsaaFbo = msaaFbo;
    }

    void MultiviewFramebufferResolve::resolveImplementation(osg::State& state)
    {
        if (mDirtyLayers)
            setupLayers();

        osg::GLExtensions* ext = state.get<osg::GLExtensions>();

        for (int view : { 0, 1 })
        {
            mResolveLayers[view]->apply(state, osg::FrameBufferObject::BindTarget::DRAW_FRAMEBUFFER);
            mMsaaLayers[view]->apply(state, osg::FrameBufferObject::BindTarget::READ_FRAMEBUFFER);
            ext->glBlitFramebuffer(0, 0, mWidth, mHeight, 0, 0, mWidth, mHeight, GL_DEPTH_BUFFER_BIT, GL_NEAREST);
        }
    }
    void MultiviewFramebufferResolve::setupLayers()
    {
        mDirtyLayers = false;
        std::vector<osg::FrameBufferObject::BufferComponent> components;
        if (mBlitMask & GL_DEPTH_BUFFER_BIT)
            components.push_back(osg::FrameBufferObject::BufferComponent::PACKED_DEPTH_STENCIL_BUFFER);
        if (mBlitMask & GL_COLOR_BUFFER_BIT)
            components.push_back(osg::FrameBufferObject::BufferComponent::COLOR_BUFFER);

        mMsaaLayers = { new osg::FrameBufferObject, new osg::FrameBufferObject };
        mResolveLayers = { new osg::FrameBufferObject, new osg::FrameBufferObject };
        for (auto component : components)
        {
            const auto& msaaAttachment = mMsaaFbo->getAttachment(component);
            mMsaaLayers[0]->setAttachment(
                component, makeSingleLayerAttachmentFromMultilayerAttachment(msaaAttachment, 0));
            mMsaaLayers[1]->setAttachment(
                component, makeSingleLayerAttachmentFromMultilayerAttachment(msaaAttachment, 1));

            const auto& resolveAttachment = mResolveFbo->getAttachment(component);
            mResolveLayers[0]->setAttachment(
                component, makeSingleLayerAttachmentFromMultilayerAttachment(resolveAttachment, 0));
            mResolveLayers[1]->setAttachment(
                component, makeSingleLayerAttachmentFromMultilayerAttachment(resolveAttachment, 1));

            mWidth = msaaAttachment.getTexture()->getTextureWidth();
            mHeight = msaaAttachment.getTexture()->getTextureHeight();
        }
    }

#ifdef OSG_HAS_MULTIVIEW
    namespace
    {
        struct MultiviewFrustumCallback final : public osg::CullSettings::InitialFrustumCallback
        {
            MultiviewFrustumCallback(Stereo::InitialFrustumCallback* ifc)
                : mIfc(ifc)
            {
            }

            void setInitialFrustum(osg::CullStack& cullStack, osg::Polytope& frustum) const override
            {
                bool nearCulling = false;
                bool farCulling = false;
                osg::BoundingBoxd bb;
                mIfc->setInitialFrustum(cullStack, bb, nearCulling, farCulling);
                frustum.setToBoundingBox(bb, nearCulling, farCulling);
            }

            Stereo::InitialFrustumCallback* mIfc;
        };
    }
#endif

    InitialFrustumCallback::InitialFrustumCallback(osg::Camera* camera)
        : mCamera(camera)
    {
#ifdef OSG_HAS_MULTIVIEW
        camera->setInitialFrustumCallback(new MultiviewFrustumCallback(this));
#endif
    }

    InitialFrustumCallback::~InitialFrustumCallback()
    {
#ifdef OSG_HAS_MULTIVIEW
        osg::ref_ptr<osg::Camera> camera;
        if (mCamera.lock(camera))
            camera->setInitialFrustumCallback(nullptr);
#endif
    }
}