I am using Irrlicht 1.8 and when I try and setup a orthogonal projection with buildProjectionMatrixOrthoRH(), if I position the object it's (0,0) origin is the middle of the screen... I would like to have the coordinates start with the top or bottom left as the 0,0 point.

If I call draw2DPolygon() the top left is (0,0) and if I call drawIndexedTriangleFan() or draw2DVertexPrimitiveList() the center of the screen is (0,0)

I am not sure why this is, but need to get this solved.

http://irrlicht.sourceforge.net/forum/viewtopic.php?f=1&t=48773

THANK you! That did the trick!!! Odd that the developers at Irrlicht don't have the ability to choose this seems simple to add the parameter on calling the buildProjectionMatrixOrthoRH() to make it offset... :)

One last quick question, how can I change the buildProjectionMatrixOrthoOffCenterRH() to be LH()?

Thanks!

M[10] = (T)(1/(zFar-zNear));

Or call buildProjectionMatrixOrthoLH instead.

Which works if combined with your previous post (manually doing translations).

If you want the matrix to handle the translations for you, then you need L. Spiro's implementation.

One last question, I am trying to use

irr::scene::IParticleEmitter

with this custom Projection matrix and it will not render the position correctly? Do I need to make my own particle class to use this?

It renders the effect at 0,0,0 when I set position to that, but if I use 400, 0, their isn't anything on screen. Screen size is 800,600 so it should be at middle bottom of screen...

 
void NX::Effect::DrawEffect(irr::IrrlichtDevice* device,
                            irr::video::IVideoDriver* driver)
{
    NX::App* p = NX::App::Get();
    
    irr::core::matrix4 oldProjMat  = driver->getTransform(irr::video::ETS_PROJECTION);
    irr::core::matrix4 oldViewMat  = driver->getTransform(irr::video::ETS_VIEW);
    irr::core::matrix4 oldWorldMat = driver->getTransform(irr::video::ETS_WORLD);
    
    irr::core::matrix4 projMatrix;
    NX::BuildProjMatrixOrthoOffCenterRH(0.0f, p->GetAppConfig()->screenSize.Width,
                                        0.0f, p->GetAppConfig()->screenSize.Height,
                                        -1.0f, 100.0f,
                                        projMatrix);

    driver->setTransform(irr::video::ETS_PROJECTION, projMatrix);
    driver->setTransform(irr::video::ETS_VIEW,  irr::core::matrix4());
    driver->setTransform(irr::video::ETS_WORLD, irr::core::matrix4());

    if(!ps)
        ps = device->getSceneManager()->addParticleSystemSceneNode(false);
    //irr::scene::IParticleSystemSceneNode* ps = device->getSceneManager()->addParticleSystemSceneNode(false);
    //irr::scene::IParticleEmitter* em         = ps->createRingEmitter(pos, .005f, .05f);
    
    //em->setMinStartSize(irr::core::dimension2d<irr::f32>(.1f, .1f));
    //em->setMaxStartSize(irr::core::dimension2d<irr::f32>(.5f, .5f));

    //irr::scene::IParticleEmitter* em = ps->createRingEmitter(pos, 0.0f, 5.0f, irr::core::vector3df(0.0f, 0.0f, .01f));
    if(!em)
    {
        em = ps->createRingEmitter(pos, 0.0f, 1.0f, irr::core::vector3df(0.0f, 0.0f, 0.0f));
        em->setMinStartSize(irr::core::dimension2d<irr::f32>(1.0f, 1.0f));
        em->setMaxStartSize(irr::core::dimension2d<irr::f32>(1.0f, 1.0f));
        ps->setEmitter(em);
        em->drop();
    }

    //irr::scene::IParticleAffector* paf = ps->createFadeOutParticleAffector();
    if(!paf)
    {
        paf = ps->createFadeOutParticleAffector();
        ps->addAffector(paf);
        paf->drop();
        ps->setMaterialFlag(irr::video::EMF_LIGHTING, false);
        ps->setMaterialFlag(irr::video::EMF_ZWRITE_ENABLE, false);
        ps->setMaterialTexture(0, driver->getTexture("media/portal6.png"));
        ps->setMaterialType(irr::video::EMT_TRANSPARENT_ADD_COLOR);
    }
    else
    {
        ps->setMaterialFlag(irr::video::EMF_LIGHTING, false);
        ps->setMaterialFlag(irr::video::EMF_ZWRITE_ENABLE, false);
        ps->setMaterialType(irr::video::EMT_TRANSPARENT_ADD_COLOR);
        driver->enableMaterial2D(true);
    }
}

Thanks!