i know what's difference between matcap shaders used in zbrush example , bidirectional radiance distribution function shader.
2 techniques same? matcap done using brdf or different?
here answer : matcap , brdf shading more usefull -2. shouldn't complain that...
from nicol bolas
assuming referring bidirectional reflectance distribution functions, brdf nothing more fancy name broad class of lighting equations. these functions compute distribution of reflectance surface based on 2 directions (bidirectional): direction of incident light , direction of viewer of surface. brdf directions both defined in terms of relative direction respect normal, normal implicit parameter.
this generalized category of lighting equations. standard lambert, blinn, phong, , forth qualify bidirectional reflectance distribution functions. can stated in terms of direction towards light , direction towards viewer.
however, since you're comparing matcap, assume referring physically based brdfs, not general category of brdfs. is, brdfs generated tables computed using machines detect light interaction properties of real materials changing view , light direction.
assuming matcap referring this, have say, no. @ least particular implementation of matcap not.
if want exceptionally generous, brdf. in loosest possible sense. why? because reflectance computed not change either of 2 directions. @ shader; directional information uses surface normal. , while property used compute color, perspective of brdf, it's constant.
if want technical, matcap uses brdf. namely, sphere texture. lighting equation is; that's reflectance distribution, based on specific view , light direction.
a proper physically-based brdf 4-dimensional lookup table, based on angles of 2 directions. matcap uses 2-dimensional lookup table, , lookup not based on either view or light direction; normal. matcap cheating, using single, static 2d slice of proper 4d brdf.
so no, matcap not brdf, code uses result of brdf color particular pixel not brdf.
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