A shadow effect can be achieved by
drawing two objects - the sharp "original" on the top
of the "shadow" (just the same object, but blurred
using feGaussianBlur
and moved a little bit).
Output
 |
| SVG version |
Source
<svg width="200" height="200" xmlns="http://www.w3.org/2000/svg" >
<defs>
<filter id="filter" filterRes="100" x="0" y="0">
<feGaussianBlur stdDeviation="4 4"/>
<feOffset dx="4" dy="4"/>
</filter>
</defs>
<rect x="4" y="4" width="100" height="100" fill="grey" filter="url(#filter)"/>
<rect x="0" y="0" width="100" height="100" fill="blue" stroke="black"/>
</svg>