Spherical Projection Iterative Solution Determine visible tiles Determine visible tiles –Tiles no longer planar, can be composed of many polygons Use bounding spheres to approximate curved tile shapes Use bounding spheres to approximate curved tile shapes Similar to vertex/frustum intersection test Similar to vertex/frustum intersection test –Hidden surface removal Back-face culling methods dont work on curved surfaces Back-face culling methods dont work on curved surfaces Additional clipping plane to divide sphere into front- and back- facing regions Additional clipping plane to divide sphere into front- and back- facing regions –Orthogonal to vector v –Need to determine distance from eye Determine tile resolution Determine tile resolution –Projecting and calculating area is difficult for curved tiles Overlapping regions not accounted for Overlapping regions not accounted for –Caclulate resolution at sample points