 | | | dot product? | dot product? 2004-06-04 - By Jean-Paul LeDoux
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I think the dot product acts correctly in 4.0 - we stumbled on this over on
the base with one of Daniel Rind's shaders.
Jean-Paul LeDoux
Northwest Imaging & FX
jp@(protected)
-- -- Original Message -- --
From: "Matt Lind" <speye_21@(protected)>
To: <xsi@(protected)>
Sent: Friday, June 04, 2004 12:19 PM
Subject: RE: dot product?
> If the docs say 'output' shader, then it's a misprint. It should say
'texture'
> shader as texture shaders are the only class of shader that can be
connected to
> almost any other type of shader in the rendertree. Output shaders are
only
> called after rendering has completed and generally only deal with the
image
> buffers and whatever 3d information may be hanging around in memory that
hasn't
> been flushed yet.
>
> As for the dot product, the vector_state node doesn't compute dot product
> correctly. What it computes, I don't know, but it certainly isn't the dot
> product. This bug has been around since version one unfortunately.
>
> However, even if the dot product were computed correctly, you might run
into a
> different problem which may be the cause of the constant red color - you
have to
> make sure all your input vectors are described in the same coordinate
space.
> Primary (eye) rays are usually described in internal space where as
geometry
> normals may sometimes be computed in object space. If a vector is coming
from
> the wrong coordinate space, there's a chance it's value doesn't change on
a
> per-ray basis because it's frame of reference is local the to component
your
> querying which is why you see the constant red. It shouldn't matter which
> coordinate space you choose to do the computations just as long all the
vectors
> are described in the same coordinate space.
>
>
> Matt
>
> -- ---- ---- ---- ---- ---- ---- ---
> Matt Lind
> Animator / Technical Director
> Softimage certified instructor:
> Softimage|3D
> Softimage|XSI
> Matt(at)Mantom.net
>
>
>
> dot product?
> Date : Fri, 04 Jun 2004 12:57:24 -0400
> To : XSI(at)Softimage.COM
> From : Sam Cuttriss <samc(at)quietman.net>
> Subject : dot product?
>
> hello, im trying to use the dot product "Vector math scalar" node in the
render
> tree.
> so i have an eyeray and a geometry normal vector state as inputs.
> the dot product is just driving a gradient mixer so i can see whats going
on,
> but im just getting constant red?
>
> the dot product help refers to vector output shaders (bumpmap generator
and
> Texture Space Controllers)
>
> are vector state shaders not output shaders?
> or is there something im doing wrong?
>
> i was expecting to see something similar to putting an incidence node
directly
> into the gradient mixer?
> thanks
> _sam
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