On 6/23/09 11:28 AM, "Tom Browder" <[email protected]> wrote:
> On Tue, Jun 23, 2009 at 10:03, Erik Greenwald<[email protected]> wrote: > ... >> Both 'gravotronic' and 'bitronic' were used as goofy placeholder names, with >> the proc-db intended to make animation sets. 'bitronic' being two control >> points moving away to show the interlinking surface and gravitronic being a >> cluster controlled by a gravity simulation to create a 'jiggly' ball. >> >> If you'd like to put effort into that proc-db, I'd appreciate it. I had >> other tasks come up that took priority. Let me know if you have questions >> about anything metaball related > > Hi, Erik, yes, can you briefly explain the parameters used to create a > metaball (is it something like a bezier curve in 3d)? I've used my > builder script to play around with some and see that they are > certainly not all non-linear. I apologize for the delay in responding, been coping with a broken wrist. The "metaball" primitive contains a method ID, threshold value, and an unordered set of control points. Each control point contains a 3d location, a "field strength", and a possibly a "blobbiness" value (called "goo" in rt_metaball_add_point). There are three method ID's defined * "metaball", which is the Tokyo Metaball approximation of the Blinn Blobby Surface. This method is not implemented yet. * "blob", the Blinn method from SIGGRAPH '82 (I think). I can dig up the journal and give you the bib info if needed. * "iso", which is a simple \Sum_{i}\frac{f_{i}}{d^{2}} computation like you'd see for computing gravitational magnitude or point charge in a basic physics course. The surface of the primitive exists where the summation of the points contribution is equal to the threshold, with the general fldstr/distance^2 pattern. The blobbiness value is only used in the blob method, and modifies the gusseting effect. In general, you should start with a threshold of 1 and a blobbiness/goo of 1 This primitive is odd in that it effectively defines values for all points in space and pretends there is a surface at the contour. It's also in an experimental/developmental stage and suspect to fundamental changes in its data structure. If I had free time, I'd be working on the proc-db to generate animations of different values changing to provide a visual demonstration, but I don't :( Hopefully that answers your questions? :) > Thanks. > > Regards, > > -Tom -Erik ------------------------------------------------------------------------------ Enter the BlackBerry Developer Challenge This is your chance to win up to $100,000 in prizes! For a limited time, vendors submitting new applications to BlackBerry App World(TM) will have the opportunity to enter the BlackBerry Developer Challenge. See full prize details at: http://p.sf.net/sfu/Challenge _______________________________________________ BRL-CAD Developer mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/brlcad-devel
