 | | | dot product? | dot product? 2004-06-04 - By Matt Lind
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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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