As for other use cases, attacks that shoot rockets might look interesting with acceleration. I think for really long range attacks, though (the thing I have in mind is the nuclear missile that I previously implemented in Military, which was able to target anywhere on the map), we'd need a way to specify the maximum speed, so that the projectile won't accelerate too fast. Rather, it'd start slow and eventually reach a max speed (very much like a real missile).
Sadly this is not for projectiles but only particles :( (unit particles and splash particles )
I may try speed-up for projectiles later.
I made a youtube video and i hope you can see what this does:
https://www.youtube.com/watch?v=jGjIlm57OTY
The "lines"
<unit-particle-system>
<texture value="true" path="images/particle.bmp" luminance="true"/>
<mode value="normal"/>
<primitive value="quad"/>
<offset x="-1" y="1" z="0.5"/>
<direction x="0.03" y="0" z="0"/>
<color red="1" green="1" blue="1" alpha="1" />
<color-no-energy red="0" green="0" blue="1" alpha="1" />
<radius value="0" />
<size value="0.1" />
<size-no-energy value="0.4" />
<speed value="2.0" />
<speedUp constant="0" relative="0.01"/> / <speedUp constant="0.01" relative="0"/>
<gravity value="0"/>
<emission-rate value="0.5" />
<energy-max value="170" />
<energy-var value="0" />
<relative value="true" />
<fixed value="true" />
<teamcolorNoEnergy value="false" />
<teamcolorEnergy value="false" />
</unit-particle-system>
The "ball":
<unit-particle-system>
<texture value="true" path="images/particle.bmp" luminance="true"/>
<mode value="normal"/>
<shape value="spherical">
<angle value="90"/>
</shape>
<primitive value="quad"/>
<offset x="0" y="0" z="1"/>
<direction x="1.0" y="0" z="0"/>
<color red="1" green="1" blue="1" alpha="1" /> / <color red="1" green="1" blue="1" alpha="0" />
<color-no-energy red="0" green="0" blue="1" alpha="1" />
<radius value="0.1" />
<size value="0.1" />
<size-no-energy value="0.4" />
<speed value="2.0" />
<speedUp constant="-0.03" relative="-0.007"/>
<gravity value="0"/>
<emission-rate value="0.5" />
<energy-max value="70" />
<energy-var value="0" />
<relative value="true" />
<fixed value="true" />
<teamcolorNoEnergy value="false" />
<teamcolorEnergy value="false" />
<alternations value="1" /> / --
</unit-particle-system>
The "Ring"
<unit-particle-system>
<texture value="true" path="images/particle.bmp" luminance="true"/>
<mode value="normal"/>
<shape value="conical">
<angle value="90" />
</shape>
<primitive value="quad"/>
<offset x="0" y="-0.9" z="0"/>
<direction x="0.0" y="1" z="0"/>
<color red="1" green="1" blue="1" alpha="1" />
<color-no-energy red="0" green="0" blue="1" alpha="1" />
<radius value="0" />
<size value="0.1" />
<size-no-energy value="0.4" />
<speed value="2.0" />
<speedUp constant="0" relative="-0.05"/>
<gravity value="0"/>
<emission-rate value="0.5" />
<energy-max value="170" />
<energy-var value="0" />
<relative value="true" />
<fixed value="true" />
<teamcolorNoEnergy value="false" />
<teamcolorEnergy value="false" />
</unit-particle-system>
The "Crown"
<unit-particle-system>
<texture value="true" path="images/particle.bmp" luminance="true"/>
<mode value="normal"/>
<shape value="conical">
<angle value="90" />
</shape>
<primitive value="quad"/>
<offset x="0" y="0.9" z="0"/>
<direction x="0.0" y="0.1" z="0"/>
<color red="1" green="1" blue="1" alpha="1" />
<color-no-energy red="0" green="0" blue="1" alpha="1" />
<radius value="0" />
<size value="0.2" />
<size-no-energy value="1" />
<speed value="2.0" />
<speedUp constant="0" relative="-0.05"/>
<gravity value="-0.05"/>
<emission-rate value="0.5" />
<energy-max value="230" />
<energy-var value="0" />
<relative value="true" />
<fixed value="true" />
<teamcolorNoEnergy value="false" />
<teamcolorEnergy value="false" />
</unit-particle-system>