Using Math in SLD file - wkt

Question

Is it possible to use math in SLD file in Geotools? I want to get Orientation for lines and calculate its sine/cosine and then multiply it with some value. But when I do this nothing shows up. Here is part polygon symbolizer that I am using.

<PolygonSymbolizer>
<Geometry>
    <ogc:Function name="buffer">
        <ogc:PropertyName>the_geom</ogc:PropertyName>
        <ogc:PropertyName>Buffer</ogc:PropertyName>
    </ogc:Function>
</Geometry>  
<Fill>
    <GraphicFill>
        <Graphic>
            <Mark>
                <WellKnownName>wkt://LINESTRING( 
                0 
                0,     
                    <ogc:Mul>
                        <ogc:PropertyName>Orientation</ogc:PropertyName>
                        <ogc:Literal>200</ogc:Literal>
                    </ogc:Mul> 
                    33 )</WellKnownName>
                <Stroke>
                    <CssParameter name="stroke">#000000</CssParameter>
                    <CssParameter name="stroke-width">1</CssParameter>
                </Stroke>
            </Mark>
        </Graphic>
    </GraphicFill>
</Fill>

Function for multiplication is

<ogc:Mul>
    <ogc:PropertyName>Orientation</ogc:PropertyName>
    <ogc:Literal>200</ogc:Literal>
</ogc:Mul> 

for sine I am not sure what function is, but it doesn't work when only multiplication is used. This is needed because when adding hatches to objects, there is need to draw a hatch with angle of 45 to one side of object. Something like this, but when object is rotated by some angle.

Answer 1

You can do math in SLD in most places, but a WellKnownMark element is not one of them.

This is what the standard says, GeoServer has a custom extension allowing to stick a CQL expression in the middle of a mark name like this:

wkt://LINESTRING(0 0, ${Orientation * 200} 33)

I could not try it out, but it should work.