Hey William y pointing down is merely a convenience thing in Lite - the native 3D coordinate system of Flash 10 has y pointing down, so lite follows suit to avoid a lot of matrix inverting. However, the main branch of Away3D has always had y pointing up, as do the majority of 3D engines.
when considering primitive construction, it is frequently desirable to have an option that constructs the geometry of a primitive so that in an untransformed state, the primtive appears upright to the user. if you're is appearing upside-down, you just need to multiple all the y coordinates you set in your primitive by -1. when you do this, the object will be turned inside out, so in order for your faces to render on the outside, you'll also need to invert either all your x coordinates or all your z coordinates to un-invert your geometry. The yUp property is there to adjust how the standard primitives are generated. If yUp is set to false, the primitive is generated with its symmetric axis pointing along the z axis. This configuration can be useful if you are using lookAt on your primitive, as the axis of the primitive (say the axis of a cylinder) is what you would consider to be the axis something uses to point at something else hope this makes things a bit clearer! Rob On Wed, Oct 6, 2010 at 12:09 PM, WillNa <[email protected]> wrote: > Hi again, > > To understand how to create vertices and faces, I'm trying to make a > basic primitive > I succeed apart one point : it faces down ! > > From what I understood, Lite uses Flash10 coordinate systems with y > pointing down so my primitive building is correct..BUT why, in this > case, any model or any other primitve (like cone) is pointing up ?! > I read Cone.as code and I don't see how this is handled....I saw the > yUP var but it switches y and z, it doesn't invert y... > > I can't rotate my scene by 180 since it will screw up others > primitives, models and cam...so what should I know to create a > primitive Lite's compliant ? > > on a side note, is the same thing on 3.6 ? > > thanks in advance > > William -- Rob Bateman Flash Development & Consultancy [email protected] www.infiniteturtles.co.uk www.away3d.com
