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

[Luke Kenneth Casson Leighton]

On Sat, Oct 5, 2019 at 3:16 PM Hendrik Boom <hendrik at topoi.pooq.com> wrote:
>
> 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.

figures.

> 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.

liikewise.  main focus: 3D, Video, at the moment.

l.