Now I just need to find the best formula to composite the =
reflection pass. Just adding reflection over doesn't produce an =
identical result. Any suggestions there?
V-
On 8/6/07, Schoenberger <XSI(at)digidragon.de> wrote:=20
Try to use the BA_color_switcher.
It supports transparencies and reflections for pass channels.
Otherwise, there is no workaround beside passes.
Holger Sch=F6nberger=20
technical director
The day has 24 hours, if that does not suffice, I will take =
the night=20
--------------------------------------------------------------------
From: owner-xsi(at)Softimage.COM =
[mailto:owner-xsi(at)Softimage.COM] On Behalf Of Votch
Sent: Sunday, August 05, 2007 10:19 PM
To: xsi(at)Softimage.COM
Subject: Buffer Channels with Transparency
I've ran into a problem using buffer channels with =
transparency.
The built in diffuse, reflection, specular, and ambient =
channels don't respect transparency at all. So I setup a custom =
rendertree and duplicated the base phong shader 4 times while disabling =
each shader compononent (diff, spec, ref) respecfully in order to =
re-create an expender version of the original shader tree. In this =
rendertree I piped each separated component into a render_Channel and =
then each render_Channel into a mix_8. When rendering out the buffers =
for this rendertree transparent parts of the shader are not represented =
correctly. In the transparent sections the "Main Buffer" rays are =
sampled.=20
The only way I've found to to separate these shader =
components successfully with transparent objects is to use passes. Then =
it works like a charm.
Does anybody know of a workaround or a way to make this =
work? Buffers are a lot easier to manage and are faster to render. But =
without sampling transparency correctly buffers are useless.=20
I've attached 3 images illustrating the 3 above scenarios =
and their corresponding scene files.
Votch Levi
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<META http-equiv=3DContent-Type content=3D"text/html; =
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<DIV><FONT face=3DArial size=3D2>the problem with screen is that it =
modulates the=20
amount that the front image gets added based on the intensities of =
the=20
background image. </FONT><FONT face=3DArial size=3D2>you cannot really =
control that=20
modulation as it is built in.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>it is a "quick and =
dirty" mode to=20
avoid burning whites, but it is very unnatural behaviour when it =
comes=20
to light.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>By darkening the background image using =
the=20
luminance of the foreground image and then adding the foreground image =
on top,=20
you can go from add to screen and anywhere in between. It just gives so =
much=20
more control.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>its like using ambocc as a multiply =
layer =20
(sure this is going to raise some eyebrows). </FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Its quick n dirty but is hardly =
the=20
best way of doing it. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Much rather use the =
(inverted) luminance of=20
the ambocc to drive a color correction.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>just my 2p, 3 eurocent or 4 =
pennies.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3DXSI(at)digidragon.de =
href=3D"mailto:XSI(at)digidragon.de">Schoenberger</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3DXSI(at)Softimage.COM=20
href=3D"mailto:XSI(at)Softimage.COM">XSI(at)Softimage.COM</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, August 08, =
2007 12:41=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> RE: Buffer Channels =
with=20
Transparency</DIV>
<DIV><BR></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D562272910-08082007><FONT =
face=3DArial=20
color=3D#000080 size=3D2></FONT></SPAN> </DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D562272910-08082007><FONT =
face=3DArial=20
color=3D#000080 size=3D2>Hi</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D562272910-08082007><FONT =
face=3DArial=20
color=3D#000080 size=3D2></FONT></SPAN> </DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D562272910-08082007><FONT =
face=3DArial=20
color=3D#000080 size=3D2></FONT></SPAN> </DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D562272910-08082007><FONT =
face=3DArial=20
color=3D#000080 size=3D2>:-) as I see there are many ways to comp=20
reflections.</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D562272910-08082007><FONT =
face=3DArial=20
color=3D#000080 size=3D2>The most used way is =
Screen.</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D562272910-08082007><FONT =
face=3DArial=20
color=3D#000080 size=3D2>This way dark areas of your object reflect =
more and=20
bright reflections are used more.</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN =
class=3D562272910-08082007></SPAN><SPAN=20
class=3D562272910-08082007></SPAN><SPAN =
class=3D562272910-08082007></SPAN><SPAN=20
class=3D562272910-08082007></SPAN><FONT face=3DArial color=3D#000080=20
size=3D2></FONT> </DIV>
<DIV dir=3Dltr align=3Dleft> </DIV>
<DIV dir=3Dltr align=3Dleft><FONT face=3DArial color=3D#000080 =
size=3D2><SPAN=20
class=3D562272910-08082007>But it depends on the shader setup of your =
scene and=20
the look.</SPAN></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><FONT face=3DArial color=3D#000080 =
size=3D2><SPAN=20
class=3D562272910-08082007>You have three choices. Try over, add or =
screen and=20
choose the one you like.</SPAN></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><FONT face=3DArial color=3D#000080 =
size=3D2><SPAN=20
class=3D562272910-08082007>If all does not look right, then you have =
to go back=20
and rethink your shader setup, perhaps there is a =
problem.</SPAN></FONT></DIV>
<DIV dir=3Dltr align=3Dleft><FONT face=3DArial color=3D#000080=20
size=3D2></FONT> </DIV>
<P align=3Dleft><FONT face=3DArial size=3D2>Holger =
Sch=F6nberger</FONT> <BR><FONT=20
face=3DArial size=3D1>technical director</FONT><BR><FONT face=3DArial =
size=3D1>The day=20
has 24 hours, if that does not suffice, I will take the night =
</FONT></P>
<DIV> </DIV><BR>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000080 2px =
solid; MARGIN-RIGHT: 0px">
<DIV class=3DOutlookMessageHeader lang=3Dde dir=3Dltr align=3Dleft>
<HR tabIndex=3D-1>
<FONT face=3DTahoma size=3D2><B>From:</B> owner-xsi(at)Softimage.COM=20
[mailto:owner-xsi(at)Softimage.COM] <B>On Behalf Of </B>peter=20
boeykens<BR><B>Sent:</B> Wednesday, August 08, 2007 9:33 =
AM<BR><B>To:</B>=20
XSI(at)Softimage.COM<BR><B>Subject:</B> Re: Buffer Channels with=20
Transparency<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV><FONT face=3DArial size=3D2>
<DIV><FONT face=3DArial size=3D2>reflections should not block out =
the surface=20
beneath it, the way they do with "over".</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>I would NOT take the =
way reflections=20
look on a standard phong shader in XSI as a reference for how =
they=20
should look.</FONT></DIV>
<DIV>
<DIV>In cg, usually dark zones in reflections end up =
darkening the=20
surface - which looks all wrong except in "mirrored reflection" =
(100%=20
reflection) </DIV>
<DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I'm looking at the reflection of =
the window on=20
my white fridge here, and d</FONT><FONT face=3DArial size=3D2>ark =
zones simply=20
do not show up in the reflections. (no light is being sent to=20
actually get reflected.)</FONT></DIV>
<DIV> </DIV>
<DIV>it definitely looks like an additive comp - though not at 100% =
- which=20
is the way I </FONT><FONT face=3DArial size=3D2>usually comp =
reflections=20
(not screen!).</FONT></DIV></DIV></DIV></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>You might need to darken the =
surface beneath it=20
a bit before doing so, <FONT face=3DArial size=3D2>theory being =
that with more light getting reflected, less of it=20
actually reaches the surface. B</FONT></FONT><FONT face=3DArial =
size=3D2>est control is by </FONT><FONT face=3DArial =
size=3D2>using the=20
luminance of the reflections as a matte for a darkening CC, =
before=20
adding the reflections. Dont overdo that darkening =
though.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>
<DIV>Note that my approach does fit the case of mirrored =
reflections,=20
that would be black underneath with reflections added in at=20
100%.</DIV></FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>just my 2p</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- =
</DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dahmidou.xsi(at)gmail.com =
href=3D"mailto:ahmidou.xsi(at)gmail.com">Ahmidou=20
Lyazidi</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3DXSI(at)Softimage.COM=20
href=3D"mailto:XSI(at)Softimage.COM">XSI(at)Softimage.COM</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, August 08, =
2007 1:30=20
AM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: Buffer =
Channels with=20
Transparency</DIV>
<DIV><BR></DIV>simply over?<BR><BR>
<DIV><SPAN class=3Dgmail_quote>2007/8/7, Votch <<A=20
=
href=3D"mailto:megavotch(at)gmail.com">megavotch(at)gmail.com</A>>:</SPAN>=20
<BLOCKQUOTE class=3Dgmail_quote=20
style=3D"PADDING-LEFT: 1ex; MARGIN: 0pt 0pt 0pt 0.8ex; =
BORDER-LEFT: rgb(204,204,204) 1px solid"><SPAN><FONT=20
face=3DArial color=3D#000080 size=3D2>Thanks for the suggestion. =
</FONT></SPAN><SPAN><FONT face=3DArial color=3D#000080=20
size=3D2>BA_color_switcher works perfectly. From now on I'm =
looking at the=20
BA collection for shader solutions before looking at the built =
in stuff=20
:) <BR><BR>Now I just need to find the best formula to composite =
the=20
reflection pass. Just adding reflection over doesn't produce an=20
identical result. Any suggestions there?<BR><SPAN=20
class=3Dsg><BR>V-<BR></SPAN></FONT></SPAN>
<DIV><SPAN class=3De id=3Dq_1144189de09a230b_3><BR>
<DIV><SPAN class=3Dgmail_quote>On 8/6/07, <B=20
class=3Dgmail_sendername>Schoenberger</B> <<A=20
onclick=3D"return top.js.OpenExtLink(window,event,this)"=20
href=3D"mailto:XSI(at)digidragon.de" =
target=3D_blank>XSI(at)digidragon.de</A>>=20
wrote:</SPAN>=20
<BLOCKQUOTE class=3Dgmail_quote=20
style=3D"PADDING-LEFT: 1ex; MARGIN: 0pt 0pt 0pt 0.8ex; =
BORDER-LEFT: rgb(204,204,204) 1px solid">
<DIV>
<DIV dir=3Dltr align=3Dleft><SPAN><FONT face=3DArial =
color=3D#000080=20
size=3D2></FONT></SPAN> </DIV>
<DIV dir=3Dltr align=3Dleft><SPAN><FONT face=3DArial =
color=3D#000080=20
size=3D2>Try to use the BA_color_switcher.</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN><FONT face=3DArial =
color=3D#000080 size=3D2>It=20
supports transparencies and reflections for pass=20
channels.</FONT></SPAN></DIV>
<DIV><FONT face=3DArial color=3D#000080=20
size=3D2><SPAN></SPAN></FONT> </DIV>
<DIV><FONT face=3DArial color=3D#000080 =
size=3D2><SPAN>Otherwise, there is=20
no workaround beside passes.</SPAN></FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Holger Sch=F6nberger</FONT> =
<BR><FONT=20
face=3DArial size=3D1>technical director</FONT><BR><FONT =
face=3DArial=20
size=3D1>The day has 24 hours, if that does not suffice, I =
will take the=20
night </FONT></DIV>
<DIV> </DIV><BR>
<BLOCKQUOTE=20
style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: =
rgb(0,0,128) 2px solid; MARGIN-RIGHT: 0px">
<DIV lang=3Dde dir=3Dltr align=3Dleft>
<HR>
<FONT face=3DTahoma size=3D2><B>From:</B> <A=20
onclick=3D"return top.js.OpenExtLink(window,event,this)"=20
href=3D"mailto:owner-xsi(at)Softimage.COM"=20
target=3D_blank>owner-xsi(at)Softimage.COM</A> [mailto:<A=20
onclick=3D"return top.js.OpenExtLink(window,event,this)"=20
href=3D"mailto:owner-xsi(at)Softimage.COM"=20
target=3D_blank>owner-xsi(at)Softimage.COM</A>] <B>On Behalf Of =
</B>Votch<BR><B>Sent:</B> Sunday, August 05, 2007 10:19=20
PM<BR><B>To:</B> <A=20
onclick=3D"return top.js.OpenExtLink(window,event,this)"=20
href=3D"mailto:xsi(at)Softimage.COM"=20
target=3D_blank>xsi(at)Softimage.COM</A><BR><B>Subject:</B> =
Buffer=20
Channels with Transparency<BR></FONT><BR></DIV>
<DIV><SPAN>
<DIV></DIV>I've ran into a problem using buffer channels =
with=20
transparency.<BR><BR>The built in diffuse, reflection, =
specular, and=20
ambient channels don't respect transparency at all. So I =
setup a=20
custom rendertree and duplicated the base phong shader 4 =
times while=20
disabling each shader compononent (diff, spec, ref) =
respecfully in=20
order to re-create an expender version of the original =
shader=20
tree. In this rendertree I piped each separated component =
into a=20
render_Channel and then each render_Channel into a mix_8. =
When=20
rendering out the buffers for this rendertree transparent =
parts of=20
the shader are not represented correctly. In the transparent =
sections the "Main Buffer" rays are sampled. <BR><BR>The =
only way=20
I've found to to separate these shader components =
successfully=20
with transparent objects is to use passes. Then it works =
like a=20
charm.<BR><BR>Does anybody know of a workaround or a way to =
make=20
this work? Buffers are a lot easier to manage and are faster =
to=20
render. But without sampling transparency correctly buffers =
are=20
useless. <BR><BR>I've attached 3 images illustrating the 3 =
above=20
scenarios and their corresponding scene files.<BR><BR>Votch=20
=
Levi<BR><BR><BR><BR></SPAN></DIV></BLOCKQUOTE></DIV></BLOCKQUOTE></DIV><B=
R></SPAN></DIV></BLOCKQUOTE></DIV><BR></BLOCKQUOTE></BLOCKQUOTE></BLOCKQU=
OTE></BODY></HTML>
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