[MAPSERVER-DEV] How to generate 3d image like GPS device?
Stephen Woodbridge
woodbri at swoodbridge.com
Mon Mar 10 14:37:28 EDT 2008
Please do not take the original jpeg I posted as the end result of what
mapserver should generate. Mapserver only should be doing the map images
and labeling if the labeling makes sense.
It would be up to the client to combine the map image with the other
screen components, in a similar fashion as OpenLayers adds a lot of GUI
elements over the base map.
So to summarize the components that I think are important:
1) the tilted perspective view of the map
2) roads and map features taper and thin with distance into the view
3) control over map viewing vector
4) readable labels if we are doing labels, flat on the map is ok, other
options might be valuable
There are lots of other things that we might want to have, so they
should be collected in a list, but lets focus on a short list of things
something like what I listed above. IE: what is the minimal useful set
to get started.
Brent,
I love some of your ideas below. Which brings me to another idea that I
have posted about in the past, and that is support for a server side
rendering library like OpenGL that has the possibility to use hardware
acceleration. But that is another mess to sort out, because it assume
that the bottleneck is in rendering instead of feeding the renderer with
data. That said, I believe OpenGL support building a display list, that
is optimized for rendering.
-Steve
Brent Fraser wrote:
> Thomas,
>
> Sharing ideas (and solutions!) is what this list is all
> about.
>
> As for advancing the implementation for 3d, it depends on
> the need. If you look at Stephen's original jpeg, there are
> a few things that make the simple X scaling a no-go:
> 1. Text labels are "up-right" instead of laid flat.
> 2. The "Y" distance is scaled as well as "X"
> 3. Other information (distance, street name) on the bottom
> dashboard and top status bar
>
> Since the display graphic is attempting to approximate the
> view you see out the windshield, somebody will ask for:
> A. Show the map draped over a DEM
> B. Render buildings (with photo textures)
> C. Show [real-time] traffic
>
> Or maybe not; sometimes simpler is better, especially when
> you are driving.
>
> (And how to implement that turn indicator symbol is a real
> interesting problem.)
>
> Anyway, with all the [potential] special non-planimetric
> stuff associate with 3d, perhaps it would be better to use
> the traditional Mapserver-generated planimetric image as
> input to a 3d navigation-graphic server. We've done some
> experimental code in VTP (www.vterrain.org) to read a GPS
> stream and display a real-time perspective view, but there
> are some limitations with that approach too
> (non-client/server, hefty graphic card requirements,
> pre-configured geographic extents, etc).
>
> Maybe adding a "post-processing" plugin capability to
> Mapserver is the way to go? That way the functionality (and
> doc, etc) could be kept logically separate from the
> traditional Mapserver. It could have it's own "map" file to
> configure the other graphic elements.
>
> In the end, will it turn into a mapper-friendly POV-Ray (not
> necessarily a bad thing)?
>
> Brent Fraser
> GeoAnalytic Inc.
> Calgary, Alberta
>
> ----- Original Message -----
> From: "thomas bonfort" <thomas.bonfort at gmail.com>
> To: <mapserver-dev at lists.osgeo.org>
> Sent: Saturday, March 08, 2008 12:30 PM
> Subject: Re: [MAPSERVER-DEV] How to generate 3d image like
> GPS device?
>
>
>> oops... just (re?)read the thread and see that I
> implemented exactly
>> what you where proposing, sorry for the paternity of that
> ;) although
>> I think that if we do go along this line, it might be more
> flexible to
>> use a real projection matrix rather than limiting
> ourselves to this
>> kind of scaling.
>>
>> rotation wrt to north facing upwards will probably be a
> bit more
>> problematic, as the letters of labels are oriented to be
> readable when
>> the map is oriented to the north and could possibly be
> upside down if
>> requesting a rotated view, but I think it may be overcome
> with a
>> specialized msTransformShapeXXX function that could
> account for the
>> rotational part of the requested view. we'd still have to
> investigate
>> how to treat the extent of the requested view wrt clipping
> of shapes
>> though.
>>
>> I'll add myself to the soc wiki page on this subject
>>
>> regards,
>> thomas
>>
>>> On Wed, Feb 27, 2008 at 5:27 PM, Brent Fraser
> <bfraser at geoanalytic.com> wrote:
>>> > Stephen,
>>> >
>>> > A cheap way to approximate the projective
> transformation
>>> > might be to apply a x-axis scaling with the scaling
> factor
>>> > varying linearly along the y-axis, basically
> squishing it at
>>> > the top. In other words, render the map image, then
>>> > resample each line of pixels (with a resampling
> value of say
>>> > 10% for the top line of pixels to 100% of the bottom
> line),
>>> > then clip and add other stuff (sky etc). Then
> there's the
>>> > problem of heading-up instead of north-up. The map
> file
>>> > does have a rotation setting, which might help.
>>> >
>>> > In the end, I think a more rigorous projective
>>> > transformation would give better results (preserving
> line
>>> > widths, etc). And there may be so many "special"
> features
>>> > that it would make more sense to have a separate
> "NavServer"
>>> > (with its own map file/API objects) instead of
>>> > warping/adding-noise to the more traditional
> MapServer to do
>>> > the task. But as Steve Lime say, it would be cool
> to see in
>>> > Mapserver. And 3d is the future...
>>> >
>>> > Brent Fraser
>>> > GeoAnalytic Inc.
>>> > Calgary, Alberta
>>> >
>>> >
>>> > ----- Original Message -----
>>> > From: "Stephen Woodbridge" <woodbri at SWOODBRIDGE.COM>
>>> > To: <MAPSERVER-DEV at LISTS.UMN.EDU>
>>> >
>>> > Sent: Wednesday, February 27, 2008 7:57 AM
>>> > Subject: Re: [MAPSERVER-DEV] How to generate 3d
> image like
>>> > GPS device?
>>> >
>>> >
>>> >
>>> >
>>> > > Tamas Szekeres wrote:
>>> > > > 2008/2/27, Stephen Woodbridge
> <woodbri at swoodbridge.com>:
>>> > > >> Hi all,
>>> > > >>
>>> > > >> Sorry for the cross posting. I need to find
> out how to
>>> > make mapserver
>>> > > >> generate map images that appear like the 3D
> mode of
>>> > GPS devices. See
>>> > > >> attached image.
>>> > > >>
>>> > > >> Has anyone done this? How?
>>> > > >> Any thoughts on how to to hack the code to do
> this?
>>> > > >>
>>> > > >
>>> > > > Stephen,
>>> > > >
>>> > > > I think we should add a special renderer for
> doing such
>>> > things, and it
>>> > > > would require to do some additional coordinate
>>> > transformations for the
>>> > > > shapes and additional special effects like
> drawing the
>>> > horizon and
>>> > > > use gradient fade out for distant areas etc. I
> don't
>>> > think it would be
>>> > > > a scope of instant hack in the code.
>>> > >
>>> > > Tamas,
>>> > >
>>> > > Thank you for your response.
>>> > >
>>> > > Yes, you may be right. I think there are a variety
> of
>>> > levels of
>>> > > implementation. Initially just getting mapserver
> to render
>>> > a tilted view
>>> > > without all the special effects would be a start.
> I was
>>> > thinking of the
>>> > > possibility of hacking the projection matrix to
> achieve
>>> > this, although
>>> > > I'm not sure how or if that is possible.
>>> > >
>>> > > The image also has an implied point of viewer that
> is used
>>> > to orient
>>> > > "up" for the image.
>>> > >
>>> > > > I wonder which use case would make this option
>>> > reasonable though. Are
>>> > > > you planning to utilize a permanent
> client-server
>>> > connection with the
>>> > > > mobile application, or compile mapserver to your
> mobile
>>> > platform?
>>> > >
>>> > > Mobile devices can be Windows/Linux laptops along
> with
>>> > those normally
>>> > > thought of as mobile.
>>> > >
>>> > > Best regards,
>>> > > -Steve W
>>> > >
>>> > > > Best regards,
>>> > > >
>>> > > > Tamas
>>> >
>>>
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