> This is possible using the Rule-Rendering > also is possible to use the rule-rendering to define a rule that in a > scale interval and with a dimension interval the feature is render using > a point rendering and change in a polygon rendering when the scale grow. >
While it is possible to set up rules to achieve a similar result, it's quite a lot of work. It's also important to note that the feature I propose would mean it's still possible to use graduated or categorized renderers on a layer - again, the end result (scale/sized based filtering together with categorized rendering) would be achievable by creating a bunch of rules, but it would be a lot of work and the end result would be much more rigid.... > As I understand, the feature to suppress small/large features would be > optional. > Yes - definitely optional and off by default! > How would you define small? I guess something can already be done with > scale based visibility, but that needs preprocessing of the data and > assigning some kind of "size class". I'm thinking of using the same method as the "Suppress labelling of features smaller than" feature from the labelling engine. This gives you a choice of feature size in mm to use as a threshold, and in my experience works quite well. I think it's important to note that hiding small features isn't just about a performance win - it's also useful from a cartographic perspective. My main use case involves a large water body dataset I frequently use, which contains everything from large lakes and inlets to very small dams and reservoirs. I need to have the large features show up at all scales, but I don't want all these smaller features cluttering up my map at small scales. This feature would mean I could easily hide the little lakes from my map at small scales, but they'd show up as I zoom in. Sure, this could all be done by assigning a hierarchy to the features and setting up a bunch of rules in a rule based renderer - but it would be so much quicker and easier to just tick a box and tweak the threshold size to suit. > Another interesting thing would be to simplify features when you zoom > out. Maybe simplifying would be quicker than rendering thousands of > unnecessary vertices. Wasn't there a summer of code project with this goal a few years back? Does anyone know what the outcome of that project was? Nyall _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
