[mapserver-dev] Request for review/comments on RFC 85 (Contour Layer Rendering)

Frank Warmerdam warmerdam at pobox.com
Thu Sep 20 14:56:17 PDT 2012

On Thu, Sep 20, 2012 at 11:21 AM, thomas bonfort
<thomas.bonfort at gmail.com> wrote:
> Frank,
> By that do you mean that the generated vector features will all be
> roughly one pixel long, or that the points inside a generated line
> will be roughly one pixel away from each other?


I mean the latter - each line segment in the line string will be
roughly one pixel long.

> In the first case, this would be a major problem, as it will be
> impossible to generate labels that follow a contour line. In the
> second case, the vector renderers won't slow down noticeably on line
> data that is sampled like this.

Good, no problem for rendering labels.  I'm a bit surprised
that this density would not some problems for speed.

On Thu, Sep 20, 2012 at 11:30 AM, Stephen Woodbridge
<woodbri at swoodbridge.com> wrote:
> In the second case do the contour lines all become pixel stair steps? if
> this is the case, I would thing some smooth of the line speed things up a
> little and for labeling I would think it would generate smoother labels, but
> maybe not.
> -Steve W


The line segments will cross the pixels at a diagonal
based on interpolation between neighbouring pixels so
you don't get the vertical/horizontal stairstep effect but
you may still be getting more location variation than
is actually useful.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Software Developer

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