Engine exhaust definitions

[misha.physics]

I need some explanation help with understanding these piece:

  -- engine exhaust definitions
  vi:add_exhaust(thhovr,8,1,{x=0,y=-1.5,z=1},{x=0,y=-1,z=0})
  vi:add_exhaust(thhovr,8,1,{x=0,y=-1.5,z=-1},{x=0,y=-1,z=0})
 
  contrail_hovr = {
    srcsize = 5.0,
    srcrate = 8,
    v0 = 200,
    srcspread = 0.15,
    lifetime = 1.0,
    growthrate = 5,
    atmslowdown = 3.0,
    ltype = PARTICLE.DIFFUSE,
    levelmap = PARTICLE.LVL_PSQRT,
    lmin = 0,
    lmax = 2,
    atmsmap = PARTICLE.ATM_PLOG,
    amin = 1e-4,
    amax = 1
  }
  exhaust_hovr = {
    srcsize = 2.0,
    srcrate = 10,
    v0 = 200,
    srcspread = 0.05,
    lifetime = 0.05,
    growthrate = 8,
    atmslowdown = 1.0,
    ltype = PARTICLE.EMISSIVE,
    levelmap = PARTICLE.LVL_SQRT,
    atmsmap = PARTICLE.ATM_PLOG,
    amin = 1e-5,
    amax = 0.1
  }
  vi:add_exhauststream(thhovr,{x=0,y=-3,z=1},contrail_hovr)
  vi:add_exhauststream(thhovr,{x=0,y=-3,z=-1},contrail_hovr)
  vi:add_exhauststream(thhovr,{x=0,y=-2,z=1},exhaust_hovr)
  vi:add_exhauststream(thhovr,{x=0,y=-2,z=-1},exhaust_hovr)

What's the difference between vi:add_exhaust(thhovr,8,1,{x=0,y=-1.5,z=1},{x=0,y=-1,z=0}) and vi:add_exhauststream(thhovr,{x=0,y=-3,z=1},contrail_hovr)?

Why do the y-coordinates diiffer (namely y=-1.5 and y=-3?

What's the difference between contrail and exhaust?

How can I get just a purple plasma trail without a stream of white particles?

 

[francisdrake]

Welcome to the topic of Orbiter exhausts!

The exhaust is a static texture, usually starting at the engine nozzle and extending away from it, being bright first, then tapering off until it vanishes.

The contrail is sequence of 'volumetric' clouds, starting near the nozzle and speeding away from it, usually increasing in size, but becoming more transparent, until they fade away.

If you want a colored stream, you need to provide a dds-texture for it and refer to it in the contrail-definition.

In the example below you see the flame exhaust, and further down the contrail:

 

[misha.physics]

Thanks.
I understood all experimentally.
vi:add_exhaust(thhovr,8,1,{x=0,y=-1.5,z=1},{x=0,y=-1,z=0}) is for flame.
vi:add_exhauststream(thhovr,{x=0,y=-3,z=1},contrail_hovr) is for "clouds" for contrail.
vi:add_exhauststream(thhovr,{x=0,y=-2,z=1},exhaust_hovr) is for "clouds" for flame.

 

[misha.physics]

Just wanted to ask if it's possible to use a custom texture for plasma flame (in a Lua script)?:

 

[johnnymanly]

oapi.register_exhausttexture("MyTexture")

 

[francisdrake]

I think to use oapi.register_exhausttexture you would need to re-compile the DeltaGlider code, is it?

To simply try a different texture, you could replace the default "Exhaust.dds" with a texture of your liking.
But please back-up the "Exhaust.dds" first, so you can change it back.

Here are a few exhaust samples I use, in the attached zip-file. If you want to replace the default exhaust, you need to rename the one to try to "Exhaust.dds", overwriting the default one.

 

[misha.physics]

Thanks, it looks amazing.

I think to use oapi.register_exhausttexture you would need to re-compile the DeltaGlider code, is it?

Actually, I meant it in the context of a Lua script, not compiled DLL module.