Originally posted by: Pete
Originally posted by: CaiNaM
Originally posted by: wizboy11
n00b question, when you refer to shimmering, what are you talking about (making sure it's the right thing , and the thing i'm thinking of).
well, i believe it usually refers to mipmap transitions? usually refers to a faintly visible line that's kind of boxed around you and follows you wherever you go... that's not the effect i'm noticing in WoW tho.. it's kind of al over... hard to describe.
They're two separate things.
Texture shimmering looks like pixel popping or sparkling. This should be evident all over the screen. It's basically not enough filtering to avoid a pop or sparkle when a pixel's underlying texture changes abruptly. (With NV, forcing LOD clamp to zero in the CP should help with misbehaving games. With both NV and ATI, forcing texture quality to High in the CP/CCC should help.) This is what ppl are talking about with WoW.
(I believe a similar thing is happening with shaders and specular maps, for example with the shiny floor tiles in CSS Dust: no or not enough filtering. Edit: Actually, SSAA can help with both this and texture shimmer, so NV's mixed 8xAA mode is useful for single cards. I
think all SuperAA and SLI AA modes help, too, in that they all incorporate some degree of SSAA.)
MIP-map transitions like with bilinear or maybe bri/trylinear filtering is a generally horizontal line or lines in screenspace that's fixed relative to your viewpoint and at which (in front and behind) you can see a distinct difference in texture clarity/blurriness. It's most obvious in flat, repeated road textures, like
here. The various colors are the MIP-maps, and the transition is where two colors meet. Brilinear is an abrupt transition b/w MIP-maps. Trilinear is a smooth transition that filters across MIP-maps. Variations, like bri- and try-linear, are meant to emulate trilinear but with fewer samples, so with a lower performance penalty. On that page, "aggressive" looks like almost basic bilinear and "application" looks like trilinear; "balanced" is probably brilinear (IIRC). You can see what AF does is push the MIPmaps (and the lower-res textures in them) further away from you.
Edit: Although, yeah, all are caused by underfiltering, and texture shimmer can be a result of less-than-full trilinear leading to less-than-full filtering across MIP-maps. I was just making a distinction b/w the MIP transitions normally most visible on the ground and the general texture shimmer normally visible all over the scene.
Here's another description of the problem, with pics.