 | | | dot product? | dot product? 2004-06-04 - By Rick Walia
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I don't know if this will work but....
Since the dot product function is busted in the Vector to Scalar node:
How about getting a scalar share node in your render tree and for the Input
param,
set a scriptedOp. In your scriptedOp you can say, do your calculations for the
dot product?
You should be able to use the XSI Math functions for calculating the dot
product.
If that is broken too then you can always calculate it yourself:
u � v = |u| |v| cos θ
Where θ is the angle between the 2 vectors.
Maybe?
/R
Quoting Guy Rabiller <guy@(protected)>:
> It should also be noted that a normalized dot product is [-1...+1] range,
> and if you want to see the full range of it you have to 'remap' the values
> to [0-1] range or else you will see 'half' of the effect.
> --
> guy rabiller | 3d technical director @ LaMaison
>
>
> -- -- Original Message -- --
> From: "Matt Lind" <speye_21@(protected)>
> To: <xsi@(protected)>
> Sent: Friday, June 04, 2004 9:19 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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> >
> >
>
>
>
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