Obtaining shadow matrixes

[sparkprime]

Is there a way to get on the CPU the shadow view/projection matrixes for a particular light in the current frame? I looked but I couldn't find...

(Obviously one can get it in the shader by binding an auto param, I'm talking about getting it on the CPU)

[bstone]

You can get the default scene-wide shadow camera setup information with Ogre::SceneManager::getShadowCameraSetup() or if your lights use custom shadow projection - Ogre::Light::getCustomShadowCameraSetup(). Once you have those you can go for Ogre::Camera::getView/ProjectionMatrix().

[sparkprime]

But where do I get the shadow camera from? Do I just take any old (or new) camera and give it to the CameraSetup?

[lunkhound]

If you register a listener with the SceneManager and then provide a function for shadowTextureCasterPreViewProj(...), it will pass to you the light and the shadow camera (and an iteration index for when there are multiple shadow cameras per light). From the camera you can query (or even change if you like) the view and projection matrices.

[sparkprime]

OK that sounds like a close match for what I want, I'll give it a go. Thanks

[sparkprime]

I can't get this working, the shadow matrixes appear to be wrong. Is it possible they are not actually initialised at this point?

edit: checked the code, they should definitely be initialised...

[sparkprime]

They are moving as the light moves and as the camera moves, but when I use them to compute shadows, the shadows are all in the wrong places. So maybe it's some col/row major mismatch, or maybe something is going wrong, or maybe it's the matrixes that are wrong. I am not actually sure yet.

[sparkprime]

I'm not sure on what the difference is between

virtual void shadowTextureCasterPreViewProj (Light *light, Camera *camera, size_t iteration)
This event occurs just before the view & projection matrices are set for rendering into a shadow texture.

virtual void shadowTextureReceiverPreViewProj (Light *light, Frustum *frustum)
This event occurs just before the view & projection matrices are set for re-rendering a shadow receiver.

The latter is never called for me, and surely the matrixes are the same in both cases?

[sparkprime]

Ah of course, these matrix don't include a mapping to uv space, there has to be an extra transform to map (-1,1) to (0,1) for x and y values before you can index the shadowmap with them. Works now

[syedhs]

http://en.wikipedia.org/wiki/Rubber_duck_debugging

[sparkprime]

The dialogue with the duck took a couple of hours though