Is a cross product between the normal and tangent vectors not giving you the bi-normal vector?
On Wed, Dec 4, 2013 at 6:50 PM, Matt Lind <[email protected]> wrote: > Those calculations are for converting the normal in the normal map between > color and euler space. The normal stored in the normal map needs a basis > (ie: transform matrix) to act as a frame of reference so the renderer knows > how to orient the normals in the map to the topology . That basis is > derived from information in the Texture UV space, geometry normal, and > Tangents and BiNormals vertex color properties. > > > > I need the algorithms for the computation of the basis, and I need to know > how ultimapper compensates for the case when the binormals are not > present. For example, does ultimapper assume the basis will always be > orthogonal and do a cross product of the tangent and geometry normal to > generate the binormal? > > > > > > Matt > > > > > > > > > > > > *From:* [email protected] [mailto: > [email protected]] *On Behalf Of *francisco criado > *Sent:* Wednesday, December 04, 2013 3:36 PM > *To:* [email protected] > *Subject:* Re: tangent/binormal space computation > > > > Hi Matt, > > will this help? > > > http://softimage.wiki.softimage.com/xsidocs/tangents_binormals_SettingtheDataTypeforTangentsandBinormals.htm#Rga95703 > > > > Francisco. > > > > 2013/12/4 Matt Lind <[email protected]> > > I need to write a variant of ultimapper to support our proprietary > workflows, but our content (tangent space normal maps) currently uses the > softimage standard. I need to know the algorithms Softimage uses so I can > make an accurate conversion to our proprietary standards. > > > > Specifically, I need to know: > > > > - how the vectors are computed in the Tangents and BiNormal vertex color > properties > > - how Ultimapper does a tangent space normal transfer when only a Tangents > vertex color property exists on the hi res mesh. > > (eg; what assumptions does it make / what calculations > does it do to compensate for lack of binormals?) > > > > > > > > > > Matt > > >
