feature_offset_polygons.earth

<!--
osgEarth Sample
This one demonstrates use of the "terrainshader" extension to use 
GLSL to affect a polygon offset effect.
-->

<map name="Feature Overlay Demo" type="geocentric" version="2">
    
    <options>
        <lighting>false</lighting>
        <overlay_blending>false</overlay_blending>
        <terrain min_lod="8"/>
    </options>
    
    <extensions>
        <terrainshader>
            <description>
                A GLSL snippet that pushes the terrain back to prevent high-altitude z fighting.
            </description>          
            <code>
                <![CDATA[
                    #version 110
                    #pragma vp_entryPoint "dp_vert"        // name of entry point function
                    #pragma vp_location   "vertex_view"    // where to insert this shader in the pipeline
                    
                    varying out float tt;
                    
                    void dp_vert(inout vec4 v)
                    {
                        const float R    = 6371000.0;      // Approximate radius of the earth
                        const float dmin = 100000.0;       // Minimum vertex distance at which to apply effect
                        const float dmax = R;              // Vertex distance at which to apply maximum effect
                        const float maxOffset = 250000.0;  // Maximum offset (applied at dmax)
                        
                        float d = length(v.xyz);
                        float t = clamp( (d-dmin)/(dmax-dmin), 0.0, 1.0 );
                        float offset = t*maxOffset;
                        vec3 n = normalize(v.xyz);
                        v.xyz = v.xyz + n*offset;
                        
                        tt = t;
                    }
                ]]>
            </code>         
        </terrainshader>
    </extensions>

    <image name="world" driver="gdal">
        <url>../data/world.tif</url>
    </image>
    
    <model name="countries" driver="feature_geom">
                          
        <features name="states" driver="ogr">
            <url>../data/world.shp</url>
            <buffer distance="-0.05"/>
            <resample max_length="5.0"/>
        </features>
        
        <styles>        
            <style type="text/css">
                p1 {
                   fill:               #ffff8066;
                }       
                p2 {
                   fill:               #80ffff66;
                }   
                p3 {
                   fill:               #ff80ff66;
                }       
                p4 {
                   fill:               #ff808066;
                }     
                p5 {
                   fill:               #80ff8066;
                }                                      
            </style>
        
            <selector class="p1">
                <query>
                    <expr><![CDATA[ POP_CNTRY <= 14045470 ]]></expr>
                </query>
            </selector>
        
            <selector class="p2">
                <query>
                    <expr><![CDATA[ POP_CNTRY > 14045470 and POP_CNTRY <= 43410900 ]]></expr>
                </query>
            </selector>
            
            <selector class="p3">
                <query>
                    <expr><![CDATA[ POP_CNTRY > 43410900 and POP_CNTRY <= 97228750 ]]></expr>
                </query>
            </selector>
            
            <selector class="p4">
                <query>
                    <expr><![CDATA[ POP_CNTRY > 97228750 and POP_CNTRY <= 258833000 ]]></expr>
                </query>
            </selector>
            
            <selector class="p5">
                <query>
                    <expr><![CDATA[ POP_CNTRY > 258833000 ]]></expr>
                </query>
            </selector>
            
        </styles>
        
    </model>
</map>