secondary ray 2005-03-31 - By Alan Jones
Back
Strange that they changed that - If you wanted it a ray to remain what
it was wouldn't you just use mi_trace_continue and not bother having
another state created?
Cheers,
Alan.
On Thu, 31 Mar 2005 10:35:59 -0500, Halfdan Ingvarsson
<hingvars@(protected)> wrote:
>
> 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.
>
> - �
>
> -- --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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