[GRASS-dev] display/drivers/HTMLMAP status

[Glynn Clements]

Moritz Lennert wrote:

> > I've added a render= option to d.vect; valid values are:
> > 
> > 	g	G_plot_polygon	(default)
> > 	r	R_polygon_abs
> > 	d	D_polygon
> > 	c	D_polygon_clip
> > 
> > The descriptions simply says "Rendering method for filled polygons",
> > with no explanation. I considered adding "(developer use only)", but
> > figured that will only encourage people to try it.
> > 
> > g or c will clip to the current frame, while r and d won't. r, d, and
> > c should all work with the HTMLMAP driver (which is now working).
> > 
> > My earlier patch essentially hard-codes the r behaviour, so that's
> > redundant now.
> > 
> > The relative speed of various options in actual use would be
> > interesting, although the actual results will vary substantially
> > depending upon the data, the "screen" (window/image) size, the driver,
> > etc.
> 
> Here's a first run on two data files, varying x-mon size and zoom. Tell 
> me if you need more info, and what other tests might be helpful.

The main thing which I notice is that there really isn't that much
difference. In most of the cases, the difference is <15% (there's one
where render=c is 50% slower, but that's the outlier, and even that
isn't that big a factor, given that there's some scope for
optimisation in D_polygon_clip).

Things which would make the results more useful:

1. Disable boundaries; I'm only interested in the polygon filling
operation, and anything else just reduces the signal-to-noise ratio.

2. Use "g.region -e"; the region only matters insofar as it provides a
(relative) measure of the number of vertices which need to be
processed.

3. Figures for direct rendering (GRASS_RENDER_IMMEDIATE=TRUE).

4. Making the results more machine-readable; a CSV file (region size,
screen size, rendering method, driver) would be ideal, but second best
would be something which I can mechanically convert into that, e.g. if
each set of tests was always preceded by the driver, screen size and
region extent, so that I don't have to manually discern the context.

-- 
Glynn Clements <glynn at gclements.plus.com>