Types Reflection mapping

1 types

1.1 sphere mapping
1.2 cube mapping
1.3 healpix mapping

types
sphere mapping

sphere mapping represents sphere of incident illumination though seen in reflection of reflective sphere through orthographic camera. texture image can created approximating ideal setup, or using fisheye lens or via prerendering scene spherical mapping.

the spherical mapping suffers limitations detract realism of resulting renderings. because spherical maps stored azimuthal projections of environments represent, abrupt point of singularity (a “black hole” effect) visible in reflection on object texel colors @ or near edge of map distorted due inadequate resolution represent points accurately. spherical mapping wastes pixels in square not in sphere.

the artifacts of spherical mapping severe effective viewpoints near of virtual orthographic camera.

cube mapping

a diagram depicting apparent reflection being provided cube-mapped reflection. map projected onto surface point of view of observer. highlights in raytracing provided tracing ray , determining angle made normal, can fudged , if manually painted texture field (or if appear there depending on how texture map obtained), projected onto mapped object along rest of texture detail.



example of three-dimensional model using cube-mapped reflection

cube mapping , other polyhedron mappings address severe distortion of sphere maps. if cube maps made , filtered correctly, have no visible seams, , can used independent of viewpoint of often-virtual camera acquiring map. cube , other polyhedron maps have since superseded sphere maps in computer graphics applications, exception of acquiring image-based lighting. image-based lighting can done parallax-corrected cube maps.

generally, cube mapping uses same skybox used in outdoor renderings. cube-mapped reflection done determining vector object being viewed at. camera ray reflected surface normal of camera vector intersects object. results in reflected ray passed cube map texel provides radiance value used in lighting calculation. creates effect object reflective.

healpix mapping

healpix environment mapping similar other polyhedron mappings, can hierarchical, providing unified framework generating polyhedra better approximate sphere. allows lower distortion @ cost of increased computation.