On Wed, 2007-02-07 at 11:32 -0500, John Denker wrote: > On 02/07/2007 09:47 AM, Ron Jensen wrote: > > While working on 3D cockpit instruments I keep hitting into issues with > > internal floating point representation and the <textranslate><step> tag. > > > > The <step> tag effectively truncates the property, 29.919999999999 > > becomes 29.91, so a (3D) readout reads off one number. > > > I am proposing an new tag, <bias>, that will act like <offset> but be > > applied before <step> and <scroll> > > While the <bias> tag seems reasonable enough, the *first* step > should be to repair the <step> feature so that it performs > rounding rather than truncation. This would greatly reduce > the number of situations where <bias> would be required. > > It seems likely that this change to <step> would immediately > unbreak a goodly number of currently-broken instruments, and > unlikely that it would break any currently-working instruments. > > Leaving <step> the way it is would create a long-lasting trap > for the unwary. > > Let me put it the other way: If there is any rationale for > having <step> truncate rather than round, would somebody please > explain what it is?
How would the step function know to round to the proper number of decimal places? In the 2D instruments a printf-style statement is used, i.e. <format>%02.2f</format>. However, we're not exactly printing in <textranslate>. I thought about a "<significant-digits>" tag where we could tell <step> how to round. So we could say: <significant-digits>2</significant-digits> instead of: <bias>0.005</bias> But the code for <significant-digits>2</significant-digits> would end up just adding 0.005 to the property anyway, and having the finer grain control in <bias> may prove useful in as-yet unthought of ways. Ron ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
