Re: [Pipmak-Users] Different patches positioning

[Christian W. <cwa...@gm...>]

Andrea Viarengo wrote:
> I have tryed to compile SVN Build 144=20
> (I think this build correspond more or less to version 0.2.6, isn't it?=
)
>=20
> This build compiled with MS Visual C++ work exactly as your official ve=
rsion=20
> 0.2.6
>=20
> I have posted screenshots to=20
>=20
>  http://viarengo.altervista.org/download/Patch.zip
>=20
> You could see separation line between patches.

OK... I've studied this, and I have determined that the new behavior=20
(tested in rev. 170, probably unchanged since 155) is correct, and the=20
old behavior (in Pipmak 0.2.6) is wrong.

If that confuses you, read section 2.9 "Patches" in the reference, in=20
particular the top left part of figure 5, and the following paragraph=20
under "Advanced Placement in 3D":
   Width and height of the patch can also be speci=EF=AC=81ed in normaliz=
ed=20
units using the nw and nh parameters. Unlike w and h, which give the=20
total width and height of the patch, these parameters describe the=20
visible width and height. On panoramas and slides, this is one patch=20
pixel less than the total width or height because a margin of half a=20
pixel is cut off each side of the patch, so that the centers of the=20
outermost pixels lie on the edge, to enable a bilinearly interpolated=20
patch to blend seamlessly into a bilinearly interpolated background=20
image. This is similar to what=E2=80=99s done with the cube faces as desc=
ribed=20
under =E2=80=9CMaking Cubic Panoramas=E2=80=9D in section 2.8 =E2=80=9CCu=
bic Panoramas=E2=80=9D. As an=20
example, this means that to make a patch of the same size coincide with=20
cube face 1 (the same thing that would be accomplished by setting face =3D=
=20
1, x =3D 0, y =3D 0), you would specify anchorh =3D 0.5, anchorv =3D 0.5,=
 nx =3D=20
-1, ny =3D 1, nz =3D -1, nw =3D 2, nh =3D 2.

You're relying on a bug in Pipmak 0.2.6 that causes the 0.5 pixel offset =

to be applied in the wrong direction for patches with negative height,=20
making the patches overlap. Try giving your patches positive heights,=20
and you'll see that you get these gaps even in 0.2.6.

You should easily be able to get rid of the gaps by positioning your=20
patches using normalized coordinates (don't forget anchorh =3D 0.5,=20
anchorv =3D 0.5).

  -Christian