[mapguide-internals] MapGuide RFC 69 - Rendering Layer Styles using Style Order

[Paul Spencer]

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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>> http://lists.osgeo.org/mailman/listinfo/mapguide-internals
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>> mapguide-internals at lists.osgeo.org
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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/