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The reason such culling is not done is that traditional stencil shadows are not cast from front surfaces: // if we have a prelight model that includes all the shadows for the major world occluders, // we can limit the area references to those visible through the portals from the light center. // We can't do this in the normal case, because shadows are cast from back facing triangles, which // may be in areas not directly visible to the light projection center. if ( light->parms.prelightModel && r_useLightPortalFlow.GetBool() && light->lightShader->LightCastsShadows() ) { light->world->FlowLightThroughPortals( light ); } else { // push these points down the BSP tree into areas light->world->PushFrustumIntoTree( NULL, light, light->inverseBaseLightProject, bounds_zeroOneCube ); } Suppose there is a wall between areaA and areaB, with light in areaA. The light sees the front side of the wall in areaA, which he won't cull away no matter what, but it does not drop shadows. The back side of the wall is in areaB, which cast the shadows. But the light does not see it: it is occluded by the wall and not visible through portals. Pretty sad. |
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I think the line here must be crossed between closed (solid) and open (sheet) surfaces. If an entity is composed of closed surfaces, then we can cull away its interaction if the entity is not visible from the light (shadow-casting one, of course). The "if" above is not entirely right: it checks for prelightModel, which is the precomputed shadow for all world-area surfaces. In reality, area surfaces are not closed in most cases, thus it is not correct to prune them as suggested. However, most of the models are closed, and it is entirely OK to prune their interactions away, which could yield noticeable improvement in some cases. So the idea is to store "closed" bit for surfaces and models, and do both branches here: FlowLightThroughPortals should decide which closed entities to consider for interactions PushFrustumIntoTree should decide which non-closed entities to consider for interactions The problem is that this piece of code only decides which AREAs are visible by lights, not entities. Moreover, it is done only when light position changes: it is not done every frame. Perhaps it would make sense to run the same portal flow in idRenderWorldLocal::CreateLightDefInteractions. Instead of simply taking all entities in all areas, go through portals and take only light-visible entities among closed ones. Non-closed entities should be handled separately, e.g. by traversing areas -> entities. |
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This forum thread shows that a lot of models are not closed enough: https://forums.thedarkmod.com/index.php?/topic/20850-improving-shadow-mapping-for-210/&do=findComment&comment=458348 (or we don't be able to detect it) |
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I had logged a seperate tracker before it was suggested I like it here - - https://bugs.thedarkmod.com/view.php?id=6243 |
- Anonymous
