[osg-users] ShadowMap problem...

Wyatt Earp wyattbsearp1881 at gmail.com
Fri Nov 20 10:52:46 PST 2009


Thanks for the suggestions.  I’ll go through the steps you suggested
 A bit
more information


 

 

I use texture units 0-3 for my texturing.

I set the base texture unit for the shadows to 0 and the shadow texture unit
to 7.

 


W

 

 

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Wojciech
Lewandowski
Sent: Friday, November 20, 2009 3:58 AM
To: 'OpenSceneGraph Users'
Subject: Re: [osg-users] ShadowMap problem...

 

Hi Wyatt,

 

I have sent a response from home but somehow I cannot notice it on osg-users
list at work. You may ignore this post if you got earlier one. 

 

Thats the screenshot I wanted. It tells me that everything is correct in
shadow map generation pass. Light is found, direction seems right, shadow
map contains only back faces (front faces were culled) from light
perspective. Terrain is not rendered to shadow map only backfacing polygons
from buildings. And thats what I would expect. 

 

So at this stage everyting seems correct. Which means there a problem in
shadow map application. Here is a checklist to follow:

 

1. Make sure Texture coords / Shadow Map texture stage & sampler are not
conflicting with other textures. This can also refer to Shadow TexGen. Make
sure you don't have other TexGen producing the coords at the same tex coord
unit as shadow map coords.  Check shadow map sampler uniform names and see
if your Shaders use the same names as default StandartdShadowMap shaders. 

 

2. Try turning off programmable pipeline completely (use empty program with
override at root of the scene graph).  Shadows should draw something even in
fixed pipeline. Shadows are usually pitch dark in fixed pipeline but they
are defintiely visible. Modify shaders to output only a shadow factor on
color. This way you will know if the shadow term is computed and passed
correctly. If its drawn then see next point because lack of shadows may be
related to improper ambient term computation.

 

3. Default StandardShadowMap and LispSM shaders treat shadow term as diffuse
/ specular light filter. Ie when pixel is in shadow its only lit by ambient
color. If for some reason ambient is not computed properly then you may see
similar issues to the ones you posted. Check terrain lighting and materials
and see if they use GL_COLOR_MATERIAL attribute. GL_COLOR_MATERIAL means
that some of the material components is taken from primitive/vertex colors.
GL_COLOR_MATERIAL does not work with vertex shaders. So its important to use
materials that have all components defined internally. 

 

Hope this helps, if not, consider sending a code and models sample (you may
send it directly to my email account if you want NDA ;-)

 

Cheers,

Wojtek

----- Original Message ----- 

From: Wyatt Earp <mailto:wyattbsearp1881 at gmail.com>  

To: 'OpenSceneGraph Users' <mailto:osg-users at lists.openscenegraph.org>  

Cc: 'Wojciech <mailto:lewandowski at ai.com.pl>  Lewandowski' 

Sent: Friday, November 20, 2009 6:03 AM

Subject: RE: [osg-users] ShadowMap problem...

 

Is this what you meant?

Thanks,

W

 

 

 

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Wojciech
Lewandowski
Sent: Thursday, November 19, 2009 4:56 PM
To: 'OpenSceneGraph Users'
Subject: Re: [osg-users] ShadowMap problem...

 

Hi Wyatt,

 

Buildings getting darker while light is moving can be a normal thing it is
simply a result of normal diffuse shading. Can you move camera so close that
view frustum contains a single building ?. Ideally make it look at 45 deg
from a liitle above. Then make screenshot, with debugHUD. Its really
important whats on debug hud display.  This will tell me alot. If you have
problems with 300 kb OSG forum limit, just send this screenshot directly to
my address. 

 

Cheers,

Wojtek Lewandowski

 

 

 

From: Wyatt <mailto:wyattbsearp1881 at gmail.com>  Earp 

Sent: Thursday, November 19, 2009 10:45 PM

To: 'OpenSceneGraph <mailto:osg-users at lists.openscenegraph.org>  Users' 

Subject: Re: [osg-users] ShadowMap problem...

 

Ok... so I did what you suggested mostly... I took the osgshadow example,
add my geometry and it worked.  I added another shader on the root node of
the scenegraph, because in my app, I do that.  I took the shaders from
ShadowMap.cpp and put them into vert/frag files and loaded them into their
respective shaders.  That worked too.

 

In my application, when I load those shaders from ShadowMap.cpp and use
them, I see a change in the lighting but it isn’t what I expect.  Rather
than the objects casting shadows on the terrain, it looks like a shdow is
being cast over the objects, but it isnt'being cast on the terrain.  The
best way I can describe it is that it looks like the objects are in the sun
then a cloud floats between the sun and the object...  I don’t think a
picture will show what I mean, but here are 3 pictures with the shadow
moving progressively to the left over the object... note the white building
in the front gets darker.  But now shadows on the terrain.

 

cid:image001.png at 01CA692E.7A38B7F0

 

cid:image002.png at 01CA692E.7A38B7F0

 

 

cid:image003.png at 01CA692E.7A38B7F0

 

W

 

 

 

> -----Original Message-----

> From: osg-users-bounces at lists.openscenegraph.org [mailto:osg-users-

> bounces at lists.openscenegraph.org] On Behalf Of Jean-Sébastien Guay

> Sent: Thursday, November 12, 2009 1:45 PM

> To: OpenSceneGraph Users

> Subject: Re: [osg-users] ShadowMap problem...

> 

> Hi Wyatt,

> 

> > Any suggestions?

> 

> Not really. At this point you'll probably have to trace into OSG to

> make

> sure the shadow map traversal is getting to the right objects (i.e.

> your

> masks are set correctly), and check your shaders (perhaps even try with

> the basic shaders that LISPSM uses by default for starters). Also, try

> to start with the osgShadow example, and work up progressively to

> something similar to what you have in your app, and perhaps in the

> process you'll find out what's not working. If not, then at least

> you'll

> have a small app that can demonstrate the problem, which we might be

> able to help with.

> 

> Hope this helps,

> 

> J-S

> --

> ______________________________________________________

> Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com

>                                 http://www.cm-labs.com/

>                          http://whitestar02.webhop.org/

> _______________________________________________

> osg-users mailing list

> osg-users at lists.openscenegraph.org

> http://lists.openscenegraph.org/listinfo.cgi/osg-users-

> openscenegraph.org


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