#2 Left-handed vs Right-handed coordinate support?

Modules (11)

I've started using the cgkit module for some scientific
visualization support and the scientific data I use
generally are in a right-handed coordinate system.
I've switched RenderMan into Right-handed mode
(RiOrientation("rh")) but things such as your
coordinate arrow utility still seem to produce
left-handed axes. It also seems to be missing the
arrow-heads in the first use I've done.

I'm also wondering if this LHS vs RHS issue is
responsible for some strangeness in the more complex
coordinate transformations I'm doing with cgtypes.

Currently using v1.1 since I don't have privileges to
install new software on our networked machines.

Thanks for your attention,



  • Matthias Baas

    Matthias Baas - 2004-10-17

    Logged In: YES

    The cgtypes module only provides basic types which you can
    use to do "3D math". The math is actually independent from
    any "handedness" issue. The handedness only comes into
    play later when results are interpreted (for example, during
    The coordinate arrow utility also knows nothing about
    handedness, it just displays the current coordinate axes.

    RenderMan uses a left handed system by default. Calling
    RiOrientation("rh") only specifies that subsequent surfaces
    use a different handedness than the default. The result is
    that the normals will be flipped. However, the final image
    won't be mirrored so you still see the coordinate arrows in a
    left-handed way. So what you still need is a call like RiScale(-
    1,1,1) to mirror the final image.

    I've also noticed that the arrow heads don't get rendered
    correctly with all renderers. It renders fine with Aqsis, so it
    might be that there's a bug in the renderer you're using (is
    that 3Delight?).

  • Matthias Baas

    Matthias Baas - 2004-10-17
    • status: open --> closed

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