Hi,

On Mon, 2007-03-26 at 17:03 +0200, Carsten Neumann wrote:
>       Hi,
> 
> the "features to port" page mentions <subject> and I'd like to work on
> it (this is something new for me, which might explain some of the
> following  questions).
> - First, is somebody already working on this ?

kind of, more one level below ;-), I'm currently working on general
stage handling things like stage data storage, execution control, and 
partition reordering. So I would like to finish this one first because
it will change the way the Lightengines should work.

> - I assume the correct way to have shadows in OpenSG 2 is by adding
> additional ShadowMapEngines ?

yes, this is the idea.

> - To get an idea of how things should be done, I looked at
> SimpleShadowMapEngine, but I have trouble to understand it. What
> algorithm does it implement ? (Williams original approach, or something
> more advanced ?)

no it is just the simplest form of shadow maps.

> - It seems to do three passes, with the functions doLightPass,
> doAmbientPass, doFinalPass. Can I have a one sentence description of
> what these functions do, please? (something like: doLightPass computes
> the depth image of the scene as seen from the light source -- it
> probably does not since it seems to run last, but this is quite
> confusing as doFinalPass seems to run first ?? ). 

-lightPass   : render the depthmap
-ambientPass : render the scene with the shadow color
-finalPass   : render the scene with the lights enabled.

The 'run first' part is one thing that is going to change (become more
flexible). Currently partitions are executed in the reverse order they
are created during traversal. Which is ok if a stage creates a single
partition but results in the strange setup order you find for the shadow
engine where the partition to run last has to be created first. But this
is something I already changed in my tree so you can group partition and
create them in the logical correct way (lightPass, ambientPass,
finalPass) instead of the reverse way.

> - In OSGRenderTraversalInit.cpp there is disabled initialization code
> for ShadowSpotLight, ShadowDirectionalLight. Are these just convenience
> wrappers for a light with a ShadowMapEngine, or is there more to them ?

no they should be removed. These are leftovers from my first try and are
superseded by the light engines.

gerrit



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