[mapguide-internals] MapGuide RFC 69 - Rendering Layer Styles
scotth at mpowerinnovations.com
scotth at mpowerinnovations.com
Fri Jun 26 18:03:45 EDT 2009
So why isnt it reverswd..run the filter on the full geometry set 100 times and stylize all at once than itterating ttthrough 10000 objects aaacross 100 filters? Sorry wm6 phone..
It drops out having to itterate through 100 styles aaas well as well as 100 label types....You would have he style stored, label type stored and do a bulk filter on all geometry...and bulk stylize....It seems ludacris to itterate through geometry on a theme as the oooutside loop...at what point would anyone ver logically have more rules than geometry objects? Having the rules the outside loop would be immensly more efficient...Even if the filter werent a bulk query and literally was an inner loop over geometry half would end before 5000, all in the other scenario itterate 10000 regRDLESS
-----Original Message-----
From: Walt Welton-Lair <walt.welton-lair at autodesk.com>
Sent: Friday, June 26, 2009 3:48 PM
To: MapGuide Internals Mail List <mapguide-internals at lists.osgeo.org>
Subject: RE: [mapguide-internals] MapGuide RFC 69 - Rendering Layer Styles
100 soil types = 100 rules = 100 different filters
For each layer MapGuide does the following in the normal case:
for each feature F in layer data set (1 FDO query)
{
for each rule R in layer theme
{
evaluate filter for R against F
if success
{
apply style from rule R to feature F
break; // move to next feature
}
}
}
So yes, worst case scenario is 10000 x 100 filter evaluations for your example layer.
The actual code which does this is https://trac.osgeo.org/mapguide/browser/trunk/MgDev/Common/Stylization/DefaultStylizer.cpp.
* DefaultStylizer::StylizeVLHelper does the iteration over features (line 289)
* inside the call to adapter->Stylize (line 333) is where the iteration over the rules happens
* for example, see https://trac.osgeo.org/mapguide/browser/trunk/MgDev/Common/Stylization/PolylineAdapter.cpp
* PolylineAdapter::Stylize (line 79) is the loop over the rules
The inverse which makes draw order match rule order is:
for each rule R in layer theme
{
for each feature F in layer data set filtered against R (1 FDO query)
{
apply style from R to feature F
}
}
but this results in 100 FDO queries. Imagine an Oracle data source....
-----Original Message-----
From: scotth at mpowerinnovations.com [mailto:scotth at mpowerinnovations.com]
Sent: Friday, June 26, 2009 12:02 PM
To: Walt Welton-Lair; MapGuide Internals Mail List
Subject: RE: [mapguide-internals] MapGuide RFC 69 - Rendering Layer Styles
using Style Order
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Help me understand...
Lets say I have 10,000 soil polygons and 100 soil types to theme..how is mapguide handling this?
Does it iterate one geometry object at a time...send itself to the filter possibly 100 times until it finds a match then stylize itself...then move on to the next geometry objct and do this 9,999 more times? With a possible of 100 x 10,000 loops?
Or does it iterate through the rules as a filter and query the full geometry 100 times to stylize en masse? Which I would assume be more efficient..if it were doing this wouldnt we expect the objects to be rendered in reverse order Top theme rendered to the bottom? In the case of my roads...moving Interstates to the top or bottom doesnt seem to matter for labeling...
-----Original Message-----
From: Walt Welton-Lair <walt.welton-lair at autodesk.com>
Sent: Friday, June 26, 2009 9:39 AM
To: MapGuide Internals Mail List <mapguide-internals at lists.osgeo.org>
Subject: RE: [mapguide-internals] MapGuide RFC 69 - Rendering Layer Styles
using Style Order
They either split things up into multiple layers, as you say, or they use the rendering pass behavior in the enhanced stylization (currently no UI for the latter, so that complicates that one). Both will have similar performance impact as what's proposed in the RFC - both end up making the same number of FDO queries. And if you read ticket 618 referenced by the RFC, the number of queries is a concern.
I would love to see MapGuide be able to support this behavior. But without a good / novel approach for doing this the performance impact will be atrocious. There are customers who have themed layers with 100's of rules, and changing the default stylization behavior to have draw order match rule order will not work for those maps performance-wise. I think at minimum the RFC will need to be updated to make this behavior optional (default is off). And that means a layer definition schema change.
-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Paul Spencer
Sent: Friday, June 26, 2009 9:18 AM
To: MapGuide Internals Mail List
Subject: Re: [mapguide-internals] MapGuide RFC 69 - Rendering Layer Styles using Style Order
How would someone achieve the desired effect now? From what I
understand (and I am not a power user of mapguide by any standard of
measurement), you would need to create several layer definitions each
with a filter and theme those layers for each road class?
how would performance for:
- for each rule, construct an FDO query filtered by the rule's condition
- render all features using the rule's style
differ from having separate layers?
Yours confusedly ;)
Paul
On 25-Jun-09, at 11:06 PM, Walt Welton-Lair wrote:
> "Can some elaborate on how the server currently handles this?"
> Handles what?
>
> The current code iterates once over the features (ignore the
> compound line style example). For every feature it evaluates the
> filters defined by the rules (in the order that the rules are
> specified). Once it finds a matching rule it applies its style to
> the feature.
>
> With compound line styles we make a pass over all the features for
> each line style. So for a compound line style containing M styles
> we make M FDO queries.
>
> With rendering passes (RFC 29) we also iterate over all the layer's
> features for each rendering pass. The more passes you define the
> more queries you make.
>
> How to implement your RFC?
>
> option 1
> - Make a pass over the features for each rule.
> - During each pass only render the features that satisfy the rule
> for that pass.
> - If there are M rules you will make M FDO queries.
> => performance (speed) will be unacceptable for anything more than a
> few themes
>
> option 2
> - Make one query against all the features, remembering (in memory?)
> all the feature information (attributes / geometry) needed by
> stylization.
> - During the initial pass render the features for the first rule.
> - Iterate over the remaining rules in order, rendering the features
> for each rule.
> => performance (memory use) will be unacceptable for data sources
> containing large numbers of features
> => this approach goes against the MG architecture of not keeping
> feature data in memory during stylization (we already break that
> rule with labels which is what leads to high memory usage spikes for
> some maps)
>
> option 3
> - Allocate one image per rule.
> - Make one query against all the features, and render each feature
> into the image corresponding to the rule it satisifes.
> - Merge all images at the end.
> => performance (speed + memory) will be unacceptable for anything
> more than a few themes
>
> option 4
> ???
>
>
> ________________________________________
> From: mapguide-internals-bounces at lists.osgeo.org [mapguide-internals-bounces at lists.osgeo.org
> ] On Behalf Of Zac Spitzer [zac.spitzer at gmail.com]
> Sent: Thursday, June 25, 2009 10:36 PM
> To: MapGuide Internals Mail List
> Subject: Re: [mapguide-internals] MapGuide RFC 69 - Rendering Layer
> Styles using Style Order
>
> At the moment the only way to achieve this is to split the road
> network out into
> multiple layers which is rather ugly.
>
> Taking a road network as the example here, it's only at the
> intersections where this
> problem occurs.
>
> Can some elaborate on how the server currently handles this?
>
> z
>
> On Fri, Jun 26, 2009 at 12:28 PM, Walt
> Welton-Lair<walt.welton-lair at autodesk.com> wrote:
>> "Proposed solution: Add support to the rendering engine to render
>> layer styles in ordered passes."
>>
>> I'd like to see some concrete suggestions in the RFC on how to
>> actually do this efficiently. Just consider a conservative use
>> case - say around 10 rules.
>>
>> Walt
>> ________________________________________
>> From: mapguide-internals-bounces at lists.osgeo.org [mapguide-internals-bounces at lists.osgeo.org
>> ] On Behalf Of Zac Spitzer [zac.spitzer at gmail.com]
>> Sent: Thursday, June 25, 2009 9:29 PM
>> To: MapGuide Internals Mail List
>> Subject: [mapguide-internals] MapGuide RFC 69 - Rendering Layer
>> Styles using Style Order
>>
>> I have posted a new RFC
>>
>> http://trac.osgeo.org/mapguide/wiki/MapGuideRfc69
>>
>> --
>> Zac Spitzer -
>> http://zacster.blogspot.com
>> +61 405 847 168
>> _______________________________________________
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>
>
>
> --
> Zac Spitzer -
> http://zacster.blogspot.com
> +61 405 847 168
> _______________________________________________
> mapguide-internals mailing list
> mapguide-internals at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapguide-internals
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__________________________________________
Paul Spencer
Chief Technology Officer
DM Solutions Group Inc
http://research.dmsolutions.ca/
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