RE: [Algorithms] Perspective shadow maps problems

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Have you run into any problems with the cases that degenerate into a
traditional shadow map?

Thanks,
Gary

> -----Original Message-----
> From: Tamas Schlagl [mailto:Tam...@cl...]
> Sent: Thursday, November 21, 2002 2:04 AM
> To: gda...@li...
> Subject: Re: [Algorithms] Perspective shadow maps problems
> 
> 
> Hi!
> 
> Maybe my old psm emails help you!
> 
> I'm playing a lot with psm, and after some "hacking" i made this:
> www.clevers.com
> 
> bye, fanthomas
> 
> 
> This came form the author of the paper:
> 
> Hmm,
> 
> I am not a DX expert and I don't know your matrix class, but 
> the following
> things seem suspicious to me:
> 
> - just adding 0.5 does not map -1..1 to 0..1. Furthermore, I 
> guess that
> emulateViewport already maps to the right range, so you 
> probably don't have
> to do anything here.
> 
> - why do you compute MV*P ? Do you use row or column vectors? Usually,
> column
> vectors are used that are multiplied to the matrices from the 
> right. In that
> case, you have to compute P*MV, i.e. it first does the modelview
> transformation and then the projection.
> 
> - in post-perspective space, parallel lights become point 
> lights. So the
> post-perspective light is *not* orthogonal!
> 
> Maybe this helped,
> 
> Marc
> 
> 
> On Friday 23 August 2002 11:47, you wrote:
> > Hello!
> >
> >
> > I read your Perspective Shadow Mapping paper, after that I 
> try to use in
> > our upcoming game called Steel Of Haste ( you can see 
> screenshots & movie
> > at www.clevers.com ).
> > So I have an working version but I have a one intresting 
> problem and an
> > other question, please help me if you can!
> >
> > The problem description:
> >     The game use DX8.1 so the ppspace isn't the [-1,1]^3 cube, but
> > [-1,1],[-1,1],[0,1] cube.
> >     Definetly I use one directional light.
> >     If I do everything like you write down on your website,I have an
> > intresting effect:
> >      When I rotate  or move my camera ( the light direction not do
> > anything), the shadows start move away ( go from his 
> position, like i move
> > the
> >     light direction ). On the shadow I see something like a 
> perspective
> > distorsion from the camera.
> >      As I think this is because my light postition in 
> post-perstective
> > space isn't at a right position, but why ? Maybe becouse I do some
> > conversion on the lightpos.z ????
> >     For a quick & dirty sollution i substract from the 
> cameradirection the
> > cameradirection paraler part of light direction, after that 
> the cameradir
> > is perpendicular for the light direction,
> > and after this the shadow working perfectly, but i have 
> other atrifacts :/
> >    Do you know what is the problem ??? I included the 
> source code of the
> > matrix generation..... maybe this help a little....
> >
> > The question:
> >    In my application a lot of big objects cast shadow, so i 
> decised i not
> > move the camera back until every object (witch make shadow for the
> screen )
> > included in the camera space, but use
> > 2 shadowmap.  Do you implemented the 2 shadowmap sollution 
> ??? How this
> > working ???
> >
> >
> >
> > Thank you,
> >     Tamas Schlagl
> >
> >
> > P.S.: I hope you can read my letter, sorry, my engilsh is 
> very poor. :/
> >
> > The source code:
> >
> > //..........Get the light direction.................
> >  LightDir.Set( GETVAR(LDir[0]), GETVAR(LDir[1]), GETVAR(LDir[2]) );
> >  LightDir.Norm();
> > LightPos = -LightDir;        // At now, the lightpos must 
> be -LightDir
> > (becouse the DX can't xchange the shadowmap-z < pixel-z 
> equation... :(
> >
> > //........... my actual camera for the scene................
> >  Camera_lookAt = CameraC->GetTarget();
> >  CameraPos       =  CameraC->GetPos();
> >  CameraDir        =  Camera_lookAt - CameraPos ;
> >  CameraDir.Norm();
> >
> > // CameraDir  -= CameraDir || LightDir;                    
> //  CameraDir =
> > CameraID - ( CameraDir paraler part of LightDir )  ??????? 
> WHY ???????
> >  CameraDir.Norm();
> >  Camera_lookAt = CameraPos + CameraDir;
> >
> > ///.... setup the shadowmap camera..........
> >  CameraCamera.Ident();
> >  CameraCamera.SetupViewport( GETVAR( NearPlane ) , GETVAR( 
> FarPlane ), 1,
> > GETVAR( Fov ), 0,0,SHADOWMAP_SIZE, SHADOWMAP_SIZE );    // get the
> > nearplane & the farplane & use the real fov!
> >  CameraCamera.SetPos( CameraPos );
> >  CameraCamera.SetTarget( Camera_lookAt );
> >  CameraCamera.SetUpVector(  CameraC->GetUpVector() );
> >  Render->EmulateViewport( CameraCamera, 0, NULL );          
>   // generate
> > camera matrix & projection matrix
> >
> >  CameraMatrix = Render->GetCameraMatrix();                  
>       // get
> > the matrixes
> >  ProjMat          = Render->GetProjectionMatrix();
> >  CameraMatrix.Concat( &ProjMat );                           
>            //
> > make the viewmatrix ( MV*P )
> >
> > 
> //............................................................
> ..........
> >  LightPos.Rotate_w0( CameraMatrix );                        
>         //
> > rotate the lightpos ( x,y,z,0 ) to screenspace !
> > 
> //............................................................
> ..........
> >
> >
> > 
> //............................................................
> ..........
> > HACK! We are in DX so not [-1,1] cube ! z = [0,1] !!!
> > LightPos.z     += 0.5f;
> >  Light_lookAt = cVector( 0,0,0.5 );
> > 
> //............................................................
> ..........
> >
> > //.................................. SM 
> camera........................
> >  LightCamera.Ident();
> >  LightCamera.SetupViewport( GETVAR( LightNear ), GETVAR( 
> LightFar ), 1, 0,
> > 0,0,SHADOWMAP_SIZE,SHADOWMAP_SIZE );
> >  LightCamera.SetOrtho( true );            // ORTHOGONAL VIEW!!!
> >  LightCamera.SetPos( LightPos  );
> >  LightCamera.SetTarget( Light_lookAt );
> > LightCamera.SetUpVector(  cVector(0,0,1)  );        // Z is 
> the up vector!
> >  Render->EmulateViewport( LightCamera, GETVAR( PlaneSize ), 
> NULL );    //
> > generate LMV & LP
> >
> >  LightM  = Render->GetCameraMatrix();
> >  LightProj   = Render->GetProjectionMatrix();
> >  LightM.Concat( &LightProj );                           // 
> create the
> > LightMatrix
> >
> >  CameraCamera.SetXpos( 1 );
> >  CameraCamera.SetYpos( 1 );
> >  CameraCamera.SetWidht( SHADOWMAP_SIZE - 2 );
> >  CameraCamera.SetHeight( SHADOWMAP_SIZE - 2 );
> >  Render->SetViewport( CameraCamera, 0, &LightM );        // Use the
> CCamera
> > for the rendering to the shadowmap BUT the PROJECTION 
> MATRIX MULTIPLIDE
> > WITH THE LIGHTMATRIX!
> >
> >  LightMatrix = Render->GetCameraMatrix();
> >  LightProj   = Render->GetProjectionMatrix();
> >  LightMatrix.Concat( &LightProj );                          
>         //
> THIS
> > IS THE matrix what we use as TextureMatrix when we want to use the
> > shadowmap!
> >
> > // LightMatrix contain: MV*P*MVL*PL
> 
> --
> E-Mail:  Mar...@me...
> phone:   +49 3643 583733 (fax: -3709)
> 
> 
> 
> 
> This from Ulrich:
> 
> On Aug 23, 2002 at 03:31 +0200, Tamas Schlagl wrote:
> >
> >  The problem description:
> >      The game use DX8.1 so the ppspace isn't the [-1,1]^3 cube, but
> >  [-1,1],[-1,1],[0,1] cube.
> >      Definetly I use one directional light.
> >      If I do everything like you write down on your 
> website,I have an
> >  intresting effect:
> >       When I rotate  or move my camera ( the light direction not do
> >  anything), the shadows start move away ( go from his 
> position, like i
> move
> >  the
> >      light direction ). On the shadow I see something like 
> a perspective
> >  distorsion from the camera.
> >       As I think this is because my light postition in 
> post-perstective
> > space
> >  isn't at a right position, but why ? Maybe becouse I do 
> some conversion
> >      on the lightpos.z ????
> 
> See note below...
> 
> >  The question:
> >     In my application a lot of big objects cast shadow, so 
> i decised i not
> >  move the camera back until every object (witch make shadow for the
> screen )
> >  included in the camera space, but use
> >  2 shadowmap.  Do you implemented the 2 shadowmap sollution 
> ??? Do you
> know
> > how this
> >  working ???
> 
> I haven't thought about that really... does it work well?
> 
> >  
> //............................................................
> ..........
> > HACK! We are in DX so not [-1,1] cube ! z = [0,1] !!!
> > ..............................
> >  LightPos.z     += 0.5f;
> 
> I'm pretty sure you want this instead:
> 
>     LightPos.z = (LightPos.z + 1.0f) * 0.5f;
> 
> It's hard to say, though -- matrix math always confuses me, and to be
> honest I'm a little rusty since I haven't worked on this in a while...
> 
> --
> Thatcher Ulrich
> http://tulrich.com
> 
> 
> And some other:
> 
> Thanks for visiting my website.
> 
> I'm very grad for receiving your mail.
> My english is very poor too.
> so, I can't explain all of my website in english.
> 
> Please, look my documentation for the light matrix
> to make the perspective shadow map.
> 
> Waiting for your cool game!
> Thanks.
> 
> IMAGIRE Takashi
> 
> --------------------------------------------------------------
> --------------
> ---
> The light matrix of p.s.m. is decomposed into the following element.
> 
> m=[View][Projection][Post Space Scaling][Post View Inverse][Light
> View][Light Projection][Offset]
> 
> View:
> View matrix is to move to the position of a camera.
> 
> 0269:     D3DXVECTOR4 eye    =
> D3DXVECTOR4(0.0f,1.4f*MeshRadius,2.5f*MeshRadius,1);
> 0270:     D3DXMatrixLookAtLH(&mView, (D3DXVECTOR3*)&eye
> 0271:                              , &D3DXVECTOR3(0,0,0)
> 0272:                              , &D3DXVECTOR3(0,1,0));
> 
> Projection:
> Projection matrix is to carry out perspective transformation.
> With this matrix, you can control the field of view.
> Because this field of view of perspective has nothig to do 
> with the one of
> camera.
> You can control the field of view appropriately according to 
> the resolution
> of shadow map.
> 
> 0289:     q = 1.0f/(z_max-z_min);
> 0292:     mProjMap = D3DXMATRIX(1,0,0,0,
> 0293:                           0,1,0,0,
> 0294:                           0,0,q,1,
> 0295:                           0,0,-q*z_min,0) * mScale;
> 
> Post Space Scaling:
> This matrix scales the post perspective space
> to made the close to the world space dimension measurements.
> This projection matrix will map the z coordinates, z_min ... z_max
> in the view space to 0 ... 1.
> Since the range is narrow, matrix converts the coordinate to 
> the one which
> is easy to use.
> I adjust te parameters to make the unit vector located at the origin
> in the original world space have the almost same magnitude after
> transformed.
> 
> 0290:     float d = D3DXVec3Length((D3DXVECTOR3*)&eye);
> 0291:     D3DXMatrixScaling(&mScale, d, d, 10000.0f*d*d);
> 
> Post View Inverse:
> The matrix is the transformation from the post perspective 
> space to the
> world space.
> To get this matrix, you can use the same way to get a view matrix.
> Like the view matrix tranforms from the world space to the 
> camera space,
> you can think of the positon & direction in the post perspective space
> as the after transformed space
> (in the case of view matrix, this would be the camera space),
> and D3DXMatrixLookAtLH, the origin in post perspective space
> will be transformed to the origin in the space after projecting.
> 
> 0299:     D3DXVECTOR4 cent = D3DXVECTOR4(0,0,0,1);
> 0300:     D3DXVECTOR4 zdir = D3DXVECTOR4(0,0,1,1);
> 0301:     D3DXVECTOR4 udir = D3DXVECTOR4(0,1,0,1);
> 0302:     D3DXVec4Transform(&cent, &cent, &mVPm); D3DXVec4Scale(&cent,
> &cent, 1.0f/cent.w);
> 0303:     D3DXVec4Transform(&zdir, &zdir, &mVPm); D3DXVec4Scale(&zdir,
> &zdir, 1.0f/zdir.w);
> 0304:     D3DXVec4Transform(&udir, &udir, &mVPm); D3DXVec4Scale(&udir,
> &udir, 1.0f/udir.w);
> 0305:     D3DXMatrixLookAtLH(&mViewI, (D3DXVECTOR3*)&cent,
> (D3DXVECTOR3*)&zdir, (D3DXVECTOR3*)&udir);
> 0308:     D3DXMatrixScaling(&mSign,-1, -1,  1);
> ****:     mViewI = mViewI * mSign;
> 
> 
> Light View:
> It is the ordinary view matrix where the light is used as camera.
> 
> 0312:     const float zoom =30.f;
> 0313:     D3DXVECTOR4 eyeP;
> 0314:     D3DXVec3Transform(&eyeP,    &D3DXVECTOR3(zoom*lightDir.x,
> zoom*lightDir.y, zoom*lightDir.z),    &mVPI);
> 0315:     D3DXVec4Scale(&eyeP,    &eyeP,    1.0f/eyeP.w);
> 0316:     D3DXMatrixLookAtLH(&mLightView, (D3DXVECTOR3*)&eyeP,
> &D3DXVECTOR3(0,0,0), &D3DXVECTOR3(0,1,0));
> 
> Light Projection:
> It is the ordinary projection matrix where the light is used 
> as camera.
> This matrix can adjust the resoluton of the screen reflected 
> to a shadow
> map.
> 
> 0319:     const float lz_min =  20.0f;
> 0320:     const float lz_max = 300.0f;
> 0321:     D3DXMatrixPerspectiveFovLH(&mProjL
> 0322:         ,60.0f*PI/180.0f
> 0323:         ,1
> 0324:         ,lz_min, lz_max
> 0325:         );
> 
> Offset:
> It shifts the origin of screen to adjust the domain of screen 
> coordinate.
> p.s.m. does not use the domain that is far from the camera,
> and to use the texture effectively, this shifts the center of texture.
> 
> 0328:     D3DXMatrixTranslation(&mShift, -0.5f, 0.5f, 0);
> 0329:     mLP =mVPI * mLightView * mProjL * mShift;
> 
> 
> 
> 
> ------------------------- other ----------------------------
> 
> Looks fantastic !
> Could you outline what do you mean by "in own style" please ? 
> It really
> motivates me , could you reveal some specs (shadow map res, 
> visible range of
> scene its applied
> onto etc.) ?
> 
> Thank you for your time
> 
> Petr S.
> 
> --------------- Puvodni zprava ---------------
> Od: "Tamas Schlagl" <Tam...@cl...>
> Odpovedet: "Tamas Schlagl" <Tam...@cl...>
> Datum:  Wed, 25 Sep 2002 08:24:39 +0200
> 
> >Hello!
> >
> >
> >I'm implemented "in own style", you can see at 
> www.clevers.com (screenshots
> >& movie ).
> >This is a very clever trick for shadow maps, but make some 
> new artifacts...
> >
> >bye,
> >Tamas Schlagl
> >Lead Programmer
> >Clever's Games Ltd
> >
> >
> >----- Original Message -----
> >From: "Petr Smilek" <gu...@pr...>
> >To: <gda...@li...>
> >Sent: Tuesday, September 24, 2002 9:50 PM
> >Subject: [Algorithms] Perspective shadow maps
> >
> >
> >> Hi,
> >> does anybody successfuly implemented and used
> >> perspective shadow maps (except authors) in practice ?
> >> Is there some demo showing them in action available ?
> >> Thank you in advance.
> >>
> >> Petr S.
> >>
> >>
> >> -------------------------------------------------------
> >> This sf.net email is sponsored by:ThinkGeek
> >> Welcome to geek heaven.
> >> http://thinkgeek.com/sf
> >> _______________________________________________
> >> GDAlgorithms-list mailing list
> >> GDA...@li...
> >> https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list
> >> Archives:
> >> http://sourceforge.net/mailarchive/forum.php?forum_id=6188
> >>
> >
> >
> 
> Thanks, I'll keep trying :)
> 
> bye,
> Petr S.
> 
> --------------- Puvodni zprava ---------------
> Od: "Tamas Schlagl" <Tam...@cl...>
> Odpovedet: "Tamas Schlagl" <Tam...@cl...>
> Datum:  Thu, 26 Sep 2002 09:44:56 +0200
> 
> >Hello,
> >
> >First of all, some specs:  map res: 1024x1024, visible range: 250.
> >
> >So, I know 4 people, who implented this (psm), but everybody 
> use other
> >technics for converting the light position to post 
> perspective space...
> this
> >means "in own style" :)
> >The biggest problem with psm is the faliure of z, based on 
> perspective
> >space. To avoid this you must use vertexshaders ( add some 
> "tolerance"
> based
> >on w )....
> >
> >
> >bye,
> >Tamas Schlagl
> >
> >----- Original Message -----
> >From: "Petr Smilek" <gu...@pr...>
> >To: "Tamas Schlagl" <Tam...@cl...>
> >Sent: Wednesday, September 25, 2002 12:43 PM
> >Subject: Re: [Algorithms] Perspective shadow maps
> >
> >
> >> Looks fantastic !
> >> Could you outline what do you mean by "in own style" 
> please ? It really
> >motivates me , could you reveal some specs (shadow map res, 
> visible range
> of
> >scene its applied
> >> onto etc.) ?
> >>
> >> Thank you for your time
> >>
> >> Petr S.
> >
> >
> >
> 
> 
> 
> 
> 
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