 | | | secondary ray | secondary ray 2005-03-31 - By Halfdan Ingvarsson
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Exactly. mental images changed the semantics of the transparency ray around
version 3.2 (from a secondary to a primary ray) but the shader did not get
updated to reflect this.
- ½
-- --Original Message-- --
From: owner-xsi@(protected) [mailto:owner-xsi@(protected)]On Behalf Of Jim
Rothrock
Sent: Wednesday, 30 March, 2005 21:05
To: XSI@(protected)
Subject: Re: secondary ray
Gerbrand Nel wrote:
still feels like it shouldn't work this way, if I make something 100 %
transparent but still have highlights running on it, everything behind that
object should be a secondary ray... because it's a refraction on the
transparent object, even if the index of refraction is 1 ??? does anyone else
agree????? the funny thing is it starts working the moment you change the index
of refraction. usefull sometimes but isn't that what the sprite shader is for??
??
Without having the source code to the shader you are using, I can make a guess
about what is happening. If the relative index of refraction is not 1.0, the
ray direction must change, so the shader calls mi_trace_refraction(). If the
relative IOR is 1.0, the ray direction will not change, so mi_trace_transparent
() is called instead. This is a speed optimization. mi_trace_transparent()
will have approximately the same effect as mi_trace_refraction(result, state,
&state->dir), but transparency rays are considered to be primary rays. From the
mental ray documentation:
miRAY_PRIMARY(raytype)
is true if the raytype is a primary or a transparency ray.
--
Jim Rothrock | Stan Winston Digital | jimr@(protected)
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<DIV><SPAN class=801153515-31032005><FONT face=Arial color=#0000ff
size=2>Exactly. mental images changed the semantics of the transparency ray
around version 3.2 (from a secondary to a primary ray) but the shader did not
get updated to reflect this.</FONT></SPAN></DIV>
<DIV><SPAN class=801153515-31032005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=801153515-31032005><FONT face=Arial color=#0000ff
size=2> - ½</FONT></SPAN></DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid">
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-- --Original Message-- --<BR><B>From:</B> owner-xsi@(protected)
[mailto:owner-xsi@(protected)]<B>On Behalf Of </B>Jim
Rothrock<BR><B>Sent:</B> Wednesday, 30 March, 2005 21:05<BR><B>To:</B>
XSI@(protected)<BR><B>Subject:</B> Re: secondary
ray<BR><BR></FONT></DIV>Gerbrand Nel wrote:
<BLOCKQUOTE cite=mid003201c53503$4509c790$1600a8c0@(protected) type="cite">
<META content="MSHTML 6.00.2900.2604" name=GENERATOR>
<DIV><FONT face=Arial size=2>still feels like it shouldn't work this way,
if
I make something 100 % transparent but still have highlights running on it,
everything behind that object should be a secondary ray... because it's a
refraction on the transparent object, even if the index of refraction is 1
??? does anyone else agree????? the funny thing is it starts working the
moment you change the index of refraction. usefull sometimes but isn't that
what the sprite shader is for????</FONT></DIV></BLOCKQUOTE>Without having
the
source code to the shader you are using, I can make a guess about what is
happening. If the relative index of refraction is not 1.0, the ray
direction must change, so the shader calls mi_trace_refraction(). If
the
relative IOR is 1.0, the ray direction will not change, so
mi_trace_transparent() is called instead. This is a speed
optimization. mi_trace_transparent() will have approximately the same
effect as mi_trace_refraction(result, state, &state->dir), but
transparency rays are considered to be primary rays. From the mental
ray
documentation:<BR><BR>
<P><TT> miRAY_PRIMARY(raytype)</TT><BR>
is true if the raytype is a primary or a transparency
ray.<BR></P><PRE class=moz-signature cols="72">--
Jim Rothrock | Stan Winston Digital | <A class=moz-txt-link-abbreviated href=
"mailto:jimr@(protected)">jimr@(protected)</A>
</PRE>--- Unsubscribe? Mail Majordomo@(protected) with the following text in
body: unsubscribe xsi </BLOCKQUOTE></BODY></HTML>
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