More Advanced Particle Stuff.

So I'm trying to replicate this:

http://www.ogre3d.org/tikiwiki/tiki-ind ... ust+Effect

I can sort of follow whats going on there, however I don't see why it's a bool, or why it's wanting a frameEvent when it doesn't even use evt in the code.

I tried creating it as a void and calling it each frame, however I then get an
"System.AccessViolationException" "Attempted to read or write protected memory" error.

my version of the code is here: https://bitbucket.org/se5a/mogreoids/sr ... ult#cl-524

however I don't see why it's a bool, or why it's wanting a frameEvent when it doesn't even use evt in the code.

It's a hook to the root's FrameStarted event.


_root.FrameStarted += new FrameListener.FrameStartedHandler(FrameStarted);

[...]

private bool FrameStarted(FrameEvent evt)
{
// called at the beginning of every frame
}


oh right, ofcourse. *facepalm*

thanks. I should have seen that.

I still get an "Attempted to read or write protected memory" error.

I'm not sure how to troubleshoot this at all, since it stops at my
mRoot.StartRendering(); line.

here's my code:



private void CreateFrameListeners()
{
mRoot.FrameRenderingQueued += new FrameListener.FrameRenderingQueuedHandler(ProcessBufferedInput);
mRoot.FrameStarted += new FrameListener.FrameStartedHandler(doDust);
}

private bool doDust(FrameEvent evt)
{
float maxDist = 250.0f;
float mirrorDist = maxDist * 0.99F;
float dimFactor = 0.8f * 0.005f * 0.005f;
float maxDist2 = maxDist * maxDist;
//Camera cam =

Vector3 camPos = camera.Position;
ParticleSystem psys = sceneMgr.GetParticleSystem("spaceDust");
ParticleIterator pit = psys._getIterator();
while (!pit.End())
{
Particle particle = pit.Next;
Vector3 pos = particle.position;
particle.timeToLive = 999999.0f;
Vector3 pDir = pos - camPos;
float dist = pDir.SquaredLength;
float dim = dist * dimFactor;
particle.SetDimensions(dim, dim);
if (dist > maxDist2)
{
pDir.Normalise();
Vector3 p = camPos - pDir * mirrorDist;
particle.position = p;
}

}
return true;
}


Edit:
ok by commenting out half the lines of the above method, then uncommenting them one by one, I found it crashed when I uncommented
Particle particle = pit.Next;
seems I can't get the ParticleIterator.Next in mogre? is this a mogre bug/missing feture or should I be doing it another way?

Ok so playing around a bit more (thank god for intellisense) I've come up with this:


private bool doDust(FrameEvent evt)
{
float maxDist = 250.0f;
float mirrorDist = maxDist * 0.99F;
float dimFactor = 0.8f * 0.005f * 0.005f;
float maxDist2 = maxDist * maxDist;

Vector3 camPos = camera.Position;
ParticleSystem psys = sceneMgr.GetParticleSystem("spaceDust");
uint numpart = psys.NumParticles;
for (uint i = 0; i < numpart; i++)
{
Particle particle = psys.GetParticle(i);
Vector3 pos = particle.position;
particle.timeToLive = 999999.0f;
Vector3 pDir = pos - camPos;
float dist = pDir.SquaredLength;
float dim = dist * dimFactor;
particle.SetDimensions(dim, dim);
if (dist > maxDist2)
{
pDir.Normalise();
Vector3 p = camPos - pDir * mirrorDist;
particle.position = p;
}
}
return true;
}


it doesn't crash, though I'm not seeing anything either, need to play around a bit more, I might just have the particles too small to be visible.

Edit: ok ParticleSystem.NumParticles is always 0 which is why I'm not seeing anything. I guess I want something else there. or maybe I want to place the particle system before this gets called...

Edit2:
Yes. I need to set it to a node first, then it *has* particles to iterate through.
however it's not acting anything like it should, and seems to loose the texture and turn into little white squares after a bit. more experiments to do....

Edit3:
ok fixed the texture problem. stupid transition from ogre particle lab to project and path problems.
I think my problem now, is that this was designed for the camera to be pointing forward not down, and I need to switch some axes somewhere.

Ok it's all working now.
here's the complete current doDust function in case someone else comes along and wants to try doing the same thing:



private bool doDust(FrameEvent evt)
{
float maxDist = 250.0f;
float mirrorDist = maxDist * 0.99F;
float dimFactor = 0.00001f; // 0.8f * 0.005f * 0.005f;
float maxDist2 = maxDist * maxDist;

Vector3 camPos = CameraMan.Position;
ParticleSystem psys = sceneMgr.GetParticleSystem("spaceDust");
uint numpart = psys.NumParticles;
for (uint i = 0; i < numpart; i++)
{
Particle particle = psys.GetParticle(i);
Vector3 pos = particle.position;
particle.timeToLive = 999999.0f;

while (pos.x - camPos.x > maxDist)
pos.x -= maxDist * 2;
while (pos.x - camPos.x < -maxDist)
pos.x += maxDist * 2;
while (pos.y - camPos.y > maxDist)
pos.y -= maxDist * 2;
while (pos.y - camPos.y < -maxDist)
pos.y += maxDist * 2;
while (pos.z - camPos.z > maxDist)
pos.z -= maxDist * 2;
while (pos.z - camPos.z < -maxDist)
pos.z += maxDist * 2;

Vector3 pDir = pos - camPos;
float dist = pDir.SquaredLength;
float dim = dist * dimFactor;
particle.SetDimensions(dim, dim);
particle.position = pos; // the origional C++ code is using a reference to the particle position, we have to set the position
}
return true;
}


note, none of this is original code, other than me converting to Mogeroids. this is all Captain Nemo and zenic's code from here:
http://www.ogre3d.org/forums/viewtopic.php?t=19122

edit, ok not quite working. so close though. seems that you can go 'outside' the box that we're placing the particles in. not sure how this is happening.
Edit2: and I think I figured that out. I had "local_space false" in the particle system. I think that needs to be true.

I think my problem now, is that this was designed for the camera to be pointing forward not down, and I need to switch some axes somewhere.

You can use the method Camera.LookAt(targetWorldPosition) to point the camera to the wanted direction.

The position can be for example the world position of a scene node, which you get by SceneNode._getDerivedPosition().

yeah that is what I'm doing already.
still not quite sure what I'm doing wrong. I've posted in the origional ogre thread hoping to get some insite.

Have you tried Camera.DerivedPosition instead of Camera.Position? It looks like the original example was using world position.

Ooohh I see what you're saying, by getting camera.position I'm getting the position of the camera relitive to it's parent node, when I want the position ralitive to the world.
I'll have a mess around with it and see what I come up with.

Except nope, I am using the world position. CameraMan is a node that the camera is attached to.
with the particle system set to localspace = false, the dust particles apear to move way too fast, and then disapear, as if I've gone outside the 'box' that the particles are in.
(I did try Vector3 camPos = sceneMgr.GetCamera("Camera").DerivedPosition; to test and it's giving the same result as Vector3 camPos = CameraMan.Position;)

another thing, which may or may not be related, is that particles that are further away look bigger, and those closer look smaller.

It also looks like you're not setting the particles position anywhere. The original wiki entry was setting the position back to the particle but I don't see anything in your code snippet that sets the position back to the particle.

Ah I see, I'm creating a new Vector3 there not a reference to the particle.position. that fixes the going out of the box thing.