In his survey "affine springer fibers and affine Deligne-Lusztig varieties", Goertz gives us a tutorial session on how to use Bruhat Tits buildings to visualize subsets of affine Grassmannians or of the affine flag variety. Due to my own ignorance of the subject, I did not see the precise statements on how exactly points or facets or simplices in a building correspond to closed points in affine Grassmannians or affine flag varieties.

Start with a reductive group G over a local field of equal characteristic, and P a parahoric subgroup scheme, Pappas and Rapoport associated a twisted version of affine flag varieties. Then how can we use the Bruhat-Tits building to think about the points in this affine flag varieties? Even any point to any reference will be highly appreciated!

In his survey "affine springer fibers and affine Deligne-Lusztig varieties", Goertz gives us a tutorial session on how to use Bruhat Tits buildings to visualize subsets of affine Grassmannians or of the affine flag variety. Due to my own ignorance of the subject, I did not see the precise statements on how exactly points or facets or simplices in a building correspond to closed points in affine Grassmannians or affine flag varieties.

Start with a reductive group G over a local field of equal characteristic, and P a parahoric subgroup scheme, Pappas and Rapoport associated a twisted version of affine flag varieties. Then how can we use the Bruhat-Tits building to think about the points in this affine flag varieties? Even any point to any reference will be highly appreciated!