Particle system won't work

[TheEagle]

Can anyone tell me why this particle system simply won't work ? It works when I put fixed values for red,green,blue, but I need to bind them to properties to allow runtime selection of the smoke color:

Code: Select all

<PropertyList>
   <particlesystem>
      <name>smoke</name>
      <texture>smoke.png</texture>
      
      <!--<condition>
         <property>sim/multiplay/generic/int[6]</property>
      </condition>-->
      
      <emissive>false</emissive>
      <lighting>false</lighting>
      <align>billboard</align>
      <attach>world</attach>
      
      <placer>
         <type>point</type>
      </placer>
      
      <shooter>
         <theta-min-deg>10</theta-min-deg>
         <theta-max-deg>86</theta-max-deg>
         <phi-min-deg>-1.5</phi-min-deg>
         <phi-max-deg>8</phi-max-deg>
         <speed-mps>
            <value>10</value>
            <spread>2.5</spread>
         </speed-mps>
      </shooter>
      
      <counter>
         <particles-per-sec>
            <value>50</value>
            <spread>1</spread>
         </particles-per-sec>
      </counter>
      
      <particle>
         <start>
            <color>
               <red><property>sim/model/smoke/red</property></red>
               <green><property>sim/model/smoke/green</property></green>
               <blue><property>sim/model/smoke/blue</property></blue>
               <alpha><value>0.3</value></alpha>
            </color>
            <size>
               <value>0.3</value>
            </size>
         </start>
         <end>
            <color>
               <red><property>sim/model/smoke/red</property></red>
               <green><property>sim/model/smoke/green</property></green>
               <blue><property>sim/model/smoke/blue</property></blue>
               <alpha><value>0.001</value></alpha>
            </color>
            <size>
               <value>30.0</value>
            </size>
         </end>
         <life-sec>
            <value>100</value>
         </life-sec>
         <mass-kg>0.001</mass-kg>
         <radius-m>1.0</radius-m>
      </particle>
      
      <program>
         <fluid>air</fluid>
         <gravity>true</gravity>
         <wind>true</wind>
      </program>
   </particlesystem>
</PropertyList>


I get no errors, but no particles either …

[Thorsten]

Probably you're not writing

Code: Select all

sim/model/smoke/red

but rather

Code: Select all

/sim/model/smoke/red

and so the particle system receives NaN as a color. Usually it's something like that.

[TheEagle]

Well, relative properties refer to the property tree root / when used in the aircraft that I'm currently flying, right ? And I have checked that /sim/model/smoke/red is set to a number (0), as well as the two other color props …

[TheEagle]

Could it be that you can't mix properties and values in the color definitions ? I have pointed red,green,blue to properties but as you can see in the code the alpha channel is a fixed value.

[TheEagle]

It works now … after setting <gravity> back to false !!! Now, can anyone tell me why it only works without gravity ???

[wkitty42]

It works now … after setting <gravity> back to false !!! Now, can anyone tell me why it only works without gravity ???

trace the code, grasshopper... trace the code... there might be a typo or it could be on purpose...
what influence do you think gravity would have?
does the volcano code have gravity?
what about the "Jurassic Park" waterfalls in Hawaii?

[Thorsten]

Well, relative properties refer to the property tree root / when used in the aircraft that I'm currently flying, right ?

Yes, but you didn't write where your particle system resides, so it was a plausible guess.

Generally using property control for colors works fine, I've done it in more than one context, so chances are the code is doing something which you don't expect. The most likely scenario is that it's not reading the properties you think it reads, but there's also more subtle issues possible.

Finally, when all else is ruled out, I think it's safe to say that the particle system has a number of genuine bugs (which we can't work around because they reside inside the OSG codebase).

[erik]

Finally, when all else is ruled out, I think it's safe to say that the particle system has a number of genuine bugs (which we can't work around because they reside inside the OSG codebase).

James has reworked the code in such a way that it is quite acceptable now. I don ´t think there are any real bugs remaining.

Erik

[TheEagle]

Well, the color control works just fine now. But when I change <gravity>false</gravity> to <gravity>true</gravity> or <gravity type="bool">true</gravity>, it simply stops working. The worst thing is - I have successfully used particle systems with <gravity>true</gravity> before (https://github.com/TheFGFSEagle/FGFireworks) ! IIRC it doesn't work neither on git next as well as the 2020.3.13 release - I'll check that again though for git next.

[erik]

This could of course be a regression after the particle code work done by James.
Maybe you should take it to the mailing-list.

Erik