Powering ahead

LOD integration is done, I decided not to implement LOD biasing on the shadow because it just looks too crap at the silhouette boundary. At least if you have LOD enabled on your mesh, both your mesh and its shadow decrease in detail and so scale well. Manual LOD levels work too, my test case was turning a knot into a spaceship at a certain distance, which worked like a charm and the shadows were consistent.

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Well, the scissor optimisation is done (this limits the drawing of stencil tris to a screenspace quad representing the attenuation range of the light); I haven’t reallly noticed any frame rate improvement, but perhaps I’m just not hitting my fillrate ceiling yet. Hopefully it will be a useful addition to someone. I’m just finishing up getting LOD (manual and automatically generated) playing nicely with stencil shadows, which works really well. Right now, the shadow volume reduces in detail at the same rate as the mesh itself - personally I’m not convinced that using a lower detail volume on a higher detail mesh will look good because of the mismatch between them - the shadow edge on the caster can look shoddy enough with stencil shadows anyway without it being exaggerated by mismatched geometry.

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Woohoo, I can commit

I found the bug this morning (see what I mean about a good nights sleep?). It was actually nothing to do with my recent changes, there was an existing bug that would only show up if you had a mesh with multiple submeshes, AND you had some reason to be using a separate light cap. The indexes that had been used by this separate light cap were not being added back into the running total, so if you had more than one shadow renderable (as is the case with multiple submeshes with their own geometry) the subsequent ones would screw up.

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Just a quick update - infinite far plane projection is implemented in all the render systems now, and coupled with the vertex program extrusion I have found it’s made a big difference to the robustness of the volumes - degenerate cases (objects passing too close to the light, etc) are now a thing of the past I think. The engine automatically enables infinite far plane projection on cameras when you use either of the stencil shadow techniques, and vertex programs are available to extrude them.

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I’m currently adding vertex program extrusion into the mix, which is giving me some frame rate improvements with stencil shadows. I also have to sort out infinite far plane projection otherwise in zfail mode the dark caps get culled, since they are being projected to infinity in the vertex program. I have a weird corruption of the volume when using vertex programs on skeletally animated meshes in release mode right now, that’s puzzling me a little since they’re fine in debug mode and non-animated meshes are fine in release mode.

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Modulative texture shadows are done, they now work with directional lights and spot lights, and have some nice fade-out features meaning that the shadows fade out in the distance for directional lights, and fade out around the edges of the spotlight range for spotlights - the latter is really important since the clamping on the shadow texture would cause horrible ‘smears’ to appear on other geometry when casters hit the edge of the texture.

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Texture shadows are fundamentally working, as you can see from this forum topic. I still have to sort out the blending so that it’s not just black & white but composited on top of the existing shadow receivers. Also, the positioning of the projector / render to texture camera is not automatic yet, I’ll have to sort that out. GL projection appears to be upside down right now, which looks like a texture matrix issue.

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The last few days have been a bit fragmented, I’ve added a few additional optimisations like being able to make shadows turn off at a given distance, and I’ve implemented the D3D versions of projective textures. Ogre could actually do projective textures before, it was just a little awkward. Now you can just attach a Frustum object to the texture unit, and it does it all for you, which is pretty slick.

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It’s been a good couple of days 😀 temas indeed did fix the GL modulative shadows issue. And I woke up this morning with one of those ‘perfect clarity’ moments, where I just knew what the cause of the remaining 2 GL shadow bugs were. REM sleep, I owe you one. The tough part was going through the whole day at work knowing what it was, but not being able to test it until I got home.

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GL shadow issues

Well, I fixed the GL light state problem, and temas seems to be close to fixing the manual blend problem so we’re getting there on GL shadow support. The outstanding issues (and these are GL only, D3D does not experience them) are: Animated meshes have problems with shadow extrusion. — Both software and hardware skinned meshes have extrusion artefacts with more than 1 submesh (test case: ninja.mesh). Software blended meshes with one submesh work fine

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