[compiz] Re: [PATCH] Transparent cube

[Roi Cohen]

hi,

about the vRotate bug, i found a fix for it which makes a lot of sense
to me, it will actually make all rotations more accurate, even with
the old cube's calculations, and will fix the bug with my calculations
as a side-effect... ;-)

in paint.c lines 59-63 (applyScreenTransform) you do:
matrixRotate (transform,
                       sAttrib->vRotate,
                       1.0f - sAttrib->xRotate / 90.0f,
                       0.0f,
                       sAttrib->xRotate / 90.0f);

you use this rotation axis and not just x axis because you need to use
the "old" x axis - the axis that was before the x-rotation changed it.
the formula you use, however, isn't accurate, and with negative
xRotate values the rotation become wrong (hence the bugs with my
patches).

after doing some simple calculations, the correct way to do this
rotation is to use this line instead:
matrixRotate (transform, sAttrib->vRotate,
                  cos(sAttrib->xRotate * DEG2RAD),
                  0.0f,
                  sin(sAttrib->xRotate * DEG2RAD));

(where DEG2RAD is #define DEG2RAD (M_PI / 180.0f) and copied from matrix.c)

with this formula, all xRotate values are "supported" (negative,
positive, >90 etc), and the axis itself is always more accurate, so i
think it'd make sense to change it, even without the new cube's
calculations.

thanks,
Roi

On 4/12/07, Roi Cohen <roico.beryl at gmail.com> wrote:
> Hi,
> Recently i have worked on re-writing beryl's transparent cube, and
> ported 3d plugin to compiz.
> I'm attaching a patchset here that includes the transparent cube
> patches (i'll post the 3d plugin when i fix some problems that didn't
> happen in beryl).
> Patching order: btf-ftb.patch, clip-planes.patch, plugin-events.patch,
> cube-paint-order.patch, transparent-cube.patch.
>
> Special thanks to Dennis Kasprzyk (who originally wrote some of these
> patches to compiz, and helped me now with various things), Quinn Storm
> (who helped me with the options), and Danny Baumann (who did most of
> the events stuff).
>
> This is what my patch includes:
>
> Core Changes:
>
> - BTF / FTB masks.
> FTB mask allows compiz to paint the windows in reversed order, front
> to back. This is needed when we paint a a cube face which is reversed.
> BTF mask alone doesn't do anything, but when combined with FTB mask,
> core will first paint the screen with regular order and after that in
> reversed order; the plugin that set BTF and FTB mask together is
> responsible for preventing core from painting the window twice. This
> allows plugins to make more complicated drawing orders. This feature
> isn't needed for transparent cube, but it is needed for 3d plugin.
> This patch was originally written by Dennis Kasprzyk for beryl (who
> also gave the idea), and now re-written for compiz by me.
>
> -  Wrappable SetClippingPlanes
> Just a new wrappable function for setting clipping planes. This is
> needed for correct clipping of the cube together with 3d plugin.
> This patch was written by Dennis Kasprzyk again, and ported to compiz.
>
> Plugin changes:
>
> - Some new events code
> Specifically: Rotate sending event to cube / 3d to notify about
> rotations. This is needed for 3d to initiate, and for setting
> transparent cube on rotate only. Also, 3d sending an event to cube to
> request to paint all viewports, this is needed for handling some
> disappearing windows in 3d (the cube face becomes invisible, but the
> windows that come out 3d are still visible in small parts, but
> disappear if cube doesn't paint that viewport).
> Last, cube is sending unfold event to 3d, needed for preventing 3d to
> transform the windows in z axis when a window is between 2 viewports.
>
> - Transparent cube
> The calculations / painting code done by cube are now changed to make
> cube to paint the faces in correct drawing order, back faces first,
> front faces last.
> Of course, i disable culling and set the desktop-window opacity to
> actually make the cube transparent, and make sure cube draws all
> viewports when the cube is transparent (when the cube isn't
> transparent, only the front faces are painted).
>
>
> This screenshot of beryl shows what happens with 3d and a window that
> is on 2 different viewports. It shows why we need to change the
> clipping planes for cube. Also, it shows when setting both FTB and BTF
> is needed (notice how the 3 top-most windows of the right viewport
> should be painted FTB, and the 2 bottom-most windows should be painted
> BTF).
> http://img454.imageshack.us/my.php?image=screenshotgy4.png
> Another screeshot of the transparent-cube with 3d plugin (in beryl
> again): http://img74.imageshack.us/my.php?image=cube3dyi6.jpg
>
>
> There are some things that I'm not really sure if they work fine with
> my patch, or they have bugs:
>
> - Currently, i'm painting all the faces of the cube when using inside
> cube (only when transparent), while some faces are never visible.
> This is needed when zooming out the cube, so i think this is a good
> idea anyway, but i'd like to know what you think about it.
>
> - Unredirecting fullscreen windows is done by paintScreenRegion which
> finds the top-fullscreen window. When doing FTB drawing, it will find
> the bottom-fullscreen window, and when doing both BTF / FTB drawing,
> it'll find the top and the bottom fullscreen windows. I'm not sure
> weather this is really wrong, so again I'd like to hear your opinion
> if my patch makes bugs on this area.
>
> - The cubeCheckFTB function (checks if the next-painted face should be
> drawn with FTB flag) seems to not work in some occasions with inside
> cube (works perfectly with outside cube). I don't know why this
> happens though.
>
> - Because of the calculations-changes i made for making transparent
> cube to work, xRotate has different values now from what it used to
> have (it has the rotation of the top-most face, which means between
> -45 and 45 for 4 sided cube, between -30 and 30 for 3 sided cube etc),
> and this change results in some weird bugs when rotating the cube with
> vertical rotations.
> I looked at applyScreenTransform, and it looks like the rotation axis
> that is used for vertical rotating expects the old values of xRotate.
> This should be fixed, but i'm not sure what is the correct way to do
> vertical rotations with the "new" values. Do you have any idea how to
> properly do that?
>
> - Unfold cube doesn't work any more at all. It got broken by my new
> calculations, and i couldn't find any way to fix it. Could anyone of
> you help in fixing it?
>
> Any help is really appreciated :-)
>
> Thanks,
> Roi.
>
>