[libre-riscv-dev] [Bug 142] Vector Ops needed (DOT, Cross, Dist, normalise, CORDIC, S/LERP etc)

[Hendrik Boom]

On Sat, Oct 05, 2019 at 07:28:06AM +0000, bugzilla-daemon at libre-riscv.org wrote:
> http://bugs.libre-riscv.org/show_bug.cgi?id=142
> 
> --- Comment #2 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
> Wondering how (whether) to add vec2 cross product and if vec4 cross product
> exists.
> 
> Found this:
> 
> vec2D a, b;
> ...
> double z = a.x * b.y - b.x * a.y;
> return z;

When you get into cross products in four-dimensional space, you enter 
the mathematics of the exterior algebra, also called the "wedge 
product".  The wedge product of four-dimensional vectors turns out to 
be in a six-dimensional space.

Not likely to be useful in a 3D graphics system.

But if you're taking about homogeneous coordinates for three-space, 
that's something completely different.  I have no idea how useful that 
would be.

-- hendrik
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