**comp.graphics.algorithms**

## Subject: **Re: Lineal algebra problem**

guanaco wrote:

> Thanks, I will try that method.

>

> I am learning Renderman and having problems specifying the camera. It

> uses a left-handed system and it seems the camera is fixed and the

> "world" system is placed relative to the camera (and not vice versa).

>

yeah, ok.

left-hand coordinates are rarer, but are used sometimes...

in this case, you reverse the directions, and move the world around the

camera, the teqniques are about the same in any case.

eg:

translate the world by the inverse of the camera's offset;

rotate the world the opposite direction as the cameras rotation.

in a sense, gl is the same way, but people more often think in terms of

moving the camera than the world. in gl, we have 2 matrices, the camera

and modelview matrix, conventionally info about the info about the

camera is stored in the projection matrix, and the world translation in

the modelview. the distinction is not that drastic, and one could

fairly easily get by with a single matrix.

> cr88192 wrote:

> > "guanaco"

> > news:1145235014.461387.155400@z34g2000cwc.googlegroups.com...

> >

> > likewise, whether or not it was intentional, the space described is left

> > handed (in my experience right handed systems are more common).

> > eg:

> > opengl will leave you looking in the -Z direction by default (X right, Y

> > up);

> > most 3D engines I have seen have Z up, X right, and Y forwards;

> > ...

> >

> > but these are right handed spaces.

> >

> > > Thanks

> > >

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