OpenMW/apps/openmw/mwrender/occlusionquery.cpp

#include "occlusionquery.hpp"

#include <OgreRenderSystem.h>
#include <OgreRoot.h>
#include <OgreBillboardSet.h>

using namespace MWRender;
using namespace Ogre;

OcclusionQuery::OcclusionQuery(OEngine::Render::OgreRenderer* renderer, SceneNode* sunNode) :
    mSunTotalAreaQuery(0), mSunVisibleAreaQuery(0), mActiveQuery(0), mDoQuery(0), mSunVisibility(0)
{
    mRendering = renderer;
    mSunNode = sunNode;

    try {
        RenderSystem* renderSystem = Root::getSingleton().getRenderSystem();

        mSunTotalAreaQuery = renderSystem->createHardwareOcclusionQuery();
        mSunVisibleAreaQuery = renderSystem->createHardwareOcclusionQuery();

        mSupported = (mSunTotalAreaQuery != 0) && (mSunVisibleAreaQuery != 0);
    }
    catch (Ogre::Exception e)
    {
        mSupported = false;
    }

    if (!mSupported)
    {
        std::cout << "Hardware occlusion queries not supported." << std::endl;
        return;
    }

    // This means that everything up to RENDER_QUEUE_MAIN can occlude the objects that are tested
    const int queue = RENDER_QUEUE_MAIN+1;

    MaterialPtr matBase = MaterialManager::getSingleton().getByName("BaseWhiteNoLighting");
    MaterialPtr matQueryArea = matBase->clone("QueryTotalPixels");
    matQueryArea->setDepthWriteEnabled(false);
    matQueryArea->setColourWriteEnabled(false);
    matQueryArea->setDepthCheckEnabled(false); // Not occluded by objects
    MaterialPtr matQueryVisible = matBase->clone("QueryVisiblePixels");
    matQueryVisible->setDepthWriteEnabled(false);
    matQueryVisible->setColourWriteEnabled(false);
    matQueryVisible->setDepthCheckEnabled(true); // Occluded by objects

    mBBQueryTotal = mRendering->getScene()->createBillboardSet(1);
    mBBQueryTotal->setDefaultDimensions(150, 150);
    mBBQueryTotal->createBillboard(Vector3::ZERO);
    mBBQueryTotal->setMaterialName("QueryTotalPixels");
    mBBQueryTotal->setRenderQueueGroup(queue);
    mSunNode->attachObject(mBBQueryTotal);

    mBBQueryVisible = mRendering->getScene()->createBillboardSet(1);
    mBBQueryVisible->setDefaultDimensions(150, 150);
    mBBQueryVisible->createBillboard(Vector3::ZERO);
    mBBQueryVisible->setMaterialName("QueryVisiblePixels");
    mBBQueryVisible->setRenderQueueGroup(queue);
    mSunNode->attachObject(mBBQueryVisible);

    mRendering->getScene()->addRenderObjectListener(this);
    mDoQuery = true;
}

OcclusionQuery::~OcclusionQuery()
{
    RenderSystem* renderSystem = Root::getSingleton().getRenderSystem();
    if (mSunTotalAreaQuery) renderSystem->destroyHardwareOcclusionQuery(mSunTotalAreaQuery);
    if (mSunVisibleAreaQuery) renderSystem->destroyHardwareOcclusionQuery(mSunVisibleAreaQuery);
}

bool OcclusionQuery::supported()
{
    return mSupported;
}

void OcclusionQuery::notifyRenderSingleObject(Renderable* rend, const Pass* pass, const AutoParamDataSource* source, 
			const LightList* pLightList, bool suppressRenderStateChanges)
{
    if (!mSupported) return;

    // The following code activates and deactivates the occlusion queries
    // so that the queries only include the rendering of their intended targets

    // Close the last occlusion query
    // Each occlusion query should only last a single rendering
    if (mActiveQuery != NULL)
    {
        mActiveQuery->endOcclusionQuery();
        mActiveQuery = NULL;
    }

    // Open a new occlusion query
    if (mDoQuery == true)
    {
        if (rend == mBBQueryTotal) 
            mActiveQuery = mSunTotalAreaQuery;
        else if (rend == mBBQueryVisible) 
            mActiveQuery = mSunVisibleAreaQuery;

        if (mActiveQuery != NULL)
        {
            mActiveQuery->beginOcclusionQuery();
        }
    }
}

void OcclusionQuery::update()
{
    if (!mSupported) return;

    // Stop occlusion queries until we get their information
    // (may not happen on the same frame they are requested in)
    mDoQuery = false;

    if (!mSunTotalAreaQuery->isStillOutstanding() && !mSunVisibleAreaQuery->isStillOutstanding())
    {
        unsigned int totalPixels;
        unsigned int visiblePixels;

        mSunTotalAreaQuery->pullOcclusionQuery(&totalPixels);
        mSunVisibleAreaQuery->pullOcclusionQuery(&visiblePixels);

        if (totalPixels == 0)
        {
            // probably outside of the view frustum
            mSunVisibility = 0;
        }
        else
        {
            mSunVisibility = float(visiblePixels) / float(totalPixels);
            if (mSunVisibility > 1) mSunVisibility = 1;
        }

        mDoQuery = true;
    }
}