Get the (standard) particles information

Helper

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On 03/10/2012 at 19:30, xxxxxxxx wrote:

Ok, I found out some stuff (by trial & error)

I created a document with an emitter that shoots particles. The document also contains a Null. After attaching the following code to the emitter, the Null follows the first particle. No orientation, just position:

  
import c4d   
import struct   
  
def GetDouble(p,buffer) :   
    # each double takes up 8 bytes   
    num=struct.unpack("d",buffer[p*8:(p*8)+8])   
    return float(num[0])   
  
def main() :   
    emitter=op.GetObject()   
    # yes, the particles data is in the Tparticle tag of the emitter   
    p_tag=emitter.GetTag(c4d.Tparticle)   
    if p_tag is None: return   
       
    null=doc.SearchObject("Null")   
    if null is None:return   
       
    # GetLowlevelDataAddressR is for read-only   
    # GetLowlevelDataAddressW will allow the writing also   
    # The SDK has them badly spelled   
    # The "level" is spelled "Level" in the SDK   
    buffer=p_tag.GetLowlevelDataAddressR()   
        pos=c4d.Vector(GetDouble(0,buffer),GetDouble(1,buffer),GetDouble(2,buffer))   
    null.SetAbsPos(pos)

The SDK states that the particle information is:

Position (vector)
Direction (vector)
Wing (Vector)
Lifetime (float)
Bits (bits)

Well on the first 24 bytes of the ByteSeq buffer we have, in fact, Position:

Position.x - Bytes 0 to 7
Position.y - Bytes 8 to 15
Position.z - Bytes 16 to 23

The direction is as follows:

Direction.x - Bytes 24 to 31
Direction.y - Bytes 32 to 39
Direction.z - Bytes 40 to 47

The Wing is as follows:

Wing.x - Bytes 48 to 55
Wing.y - Bytes 56 to 63
Wing.z - Bytes 64 to 71

The direction returns what looks like the orientation of the emitter itself (kind of).
The wing... I really don't know how to interpret it. It looks like the Speed vector. But I would like that anyone more versed on particles to tell me.
From bytes 72 to 79 there is a double that grows slowly from 0.0000 in increments of 0.04 at each frame. That is consistent with my document as it is set to 25 fps, because 1/25 is 0.04
The problem is that it keeps growing even after the particle is gone.
That is because I haven't found out how to know how many particles are alive and whether the particle is alive or not. That is probably in the bits information but I really don't know how to interpret that.
So, with all I found out so far, would anyone help out into finding some more?

Helper

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On 04/10/2012 at 07:25, xxxxxxxx wrote:

Interesting Rui.
I don't have time atm to study this, so any input is most appreciated.
(Regarding Standard Particle Life , I -think- the "internal" particles are always live
but are only hidden/scaled over life. Anyone must correct me if I'm wrong)

Cheers
Lennart

Helper

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On 04/10/2012 at 08:57, xxxxxxxx wrote:

I think this post might be of interest: https://developers.maxon.net/forum/topic/5919/6005_tparticle-data-not-available-in-python&PID=26813#26813

Helper

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On 04/10/2012 at 09:23, xxxxxxxx wrote:

That solution only works if there are objects as childs of the emitter and the "Show Objects" option is on.
I want to be able to access the particle values even if there are no objects being created.
And the good news are... I DID IT!!!
Check out the code:

  
import c4d   
import struct   
  
# return the number of active particles   
def P_count(buffer) :   
    count=0   
    for i in range(len(buffer)/88) :   
        index=i*88   
        bits=int(struct.unpack("B",buffer[index+80:index+81])[0])   
        count+=(bits!=0)   
    return count   
  
# return the ALIVE value of the particle p (0 or 1)   
def P_alive(p,buffer) :   
    index=p*88   
    bits=int(struct.unpack("B",buffer[index+80:index+81])[0])   
    return (bits & 2) >> 1   
  
# return the VISIBLE value of the particle p (0 or 1)   
def P_visible(p,buffer) :   
    index=p*88   
    bits=int(struct.unpack("B",buffer[index+80:index+81])[0])   
    return (bits & 1)   
  
# returns the vector of the current position of particle p   
def P_position(p,buffer) :   
    index=p*88   
    return c4d.Vector(struct.unpack("d",buffer[index:index+8])[0],struct.unpack("d",buffer[index+8:index+16])[0],struct.unpack("d",buffer[index+16:index+24])[0])   
  
# returns the vector of the current direction of particle p   
def P_direction(p,buffer) :   
    index=p*88   
    return c4d.Vector(struct.unpack("d",buffer[index+24:index+32])[0],struct.unpack("d",buffer[index+32:index+40])[0],struct.unpack("d",buffer[index+40:index+48])[0])   
  
# returns the vector of the current wing of particle p   
def P_wing(p,buffer) :   
    index=p*88   
    return c4d.Vector(struct.unpack("d",buffer[index+48:index+56])[0],struct.unpack("d",buffer[index+56:index+64])[0],struct.unpack("d",buffer[index+64:index+72])[0])   
  
# returns the life of particle p (double)   
def P_lifetime(p,buffer) :   
    index=p*88   
    return struct.unpack("d",buffer[index+72:index+80])   
  
def main() :   
    emitter=op.GetObject()   
    p_tag=emitter.GetTag(c4d.Tparticle)   
    if p_tag is None: return   
       
    buffer=p_tag.GetLowlevelDataAddressW()   
       
    count=P_count(buffer) # gets the number of active particles   
       
    for i in range(count) :   
        print "Particle "+str(i)     # print the particle number   
        print P_alive(i,buffer)          # print the active state of the particle   
        print P_visible(i,buffer)     # print the visibility of the particle   
        print P_position(i,buffer)     # print the current position of the particle   
        print P_direction(i,buffer)     # print the current direction of the particle   
        print P_wing(i,buffer)          # print the current wing of the particle   
        print P_lifetime(i,buffer)     # print the lifespan value of the particle   
        print " "

Helper

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On 04/10/2012 at 09:25, xxxxxxxx wrote:

Now I only have two doubts.
The direction is not returning the particle direction but it is, in fact, returning a value that corresponds, somehow, to the direction of the emitter.
And I don't know how to interpret the wing value.
Could someone help me out on this?

Helper

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On 05/10/2012 at 01:10, xxxxxxxx wrote:

Originally posted by xxxxxxxx

Now I only have two doubts.
The direction is not returning the particle direction but it is, in fact, returning a value that corresponds, somehow, to the direction of the emitter.
And I don't know how to interpret the wing value.
Could someone help me out on this?

All the information you're getting about a particle is listed and explained in the members of c4d.modules.particles.Particle (Python documentation).

Helper

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On 05/10/2012 at 01:13, xxxxxxxx wrote:

Originally posted by xxxxxxxx

That solution only works if there are objects as childs of the emitter and the "Show Objects" option is on.
I want to be able to access the particle values even if there are no objects being created.
And the good news are... I DID IT!!!

Ah ok, I understand now why you couldn't use this solution. Glad you found how to read the particles data.

Helper

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On 05/10/2012 at 08:28, xxxxxxxx wrote:

However, the information in the SDK about the standard particles is almost non-existent.
Shouldn't it be more clear?

Helper

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On 08/10/2012 at 02:36, xxxxxxxx wrote:

Originally posted by xxxxxxxx

However, the information in the SDK about the standard particles is almost non-existent.
Shouldn't it be more clear?

Have you looked into the Python docs (not COFFEE) at the page for the class c4d.modules.particles.Particle? I don't think there's more to add.

Helper

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On 08/10/2012 at 05:25, xxxxxxxx wrote:

Yes, I have looked into it, Yannick.
It tells me what information is present but it doesn't tell me where it is, how to get it, etc.

Helper

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On 08/10/2012 at 06:03, xxxxxxxx wrote:

Originally posted by xxxxxxxx

However, the information in the SDK about the standard particles is almost non-existent.
Shouldn't it be more clear?

Yes, it should.

Cheers,
André

Helper

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On 08/10/2012 at 07:53, xxxxxxxx wrote:

Also, besides not telling us how to get the raw data, it doesn't tells us how to get the elements out of the data.
As you can see from my exemplar above, it is not a straightforward method.

Rui Batista

Helper

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On 08/10/2012 at 09:03, xxxxxxxx wrote:

Originally posted by xxxxxxxx

Also, besides not telling us how to get the raw data, it doesn't tells us how to get the elements out of the data.
As you can see from my exemplar above, it is not a straightforward method.

Rui Batista

The C++ documentation states that the array of particles is private (ParticleTag docs' page).
In fact the issue is: the C++ SDK's ParticleObject class isn't wrapped in Python. This class allows to easily access the particle array without having to figure how the particles are stored in memory.

Helper

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On 08/10/2012 at 09:37, xxxxxxxx wrote:

So, should it be in the python SDK in the current form?
Because, as it is now, it shows information that is not accessible directly.

Rui Batista

Helper

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On 09/10/2012 at 01:42, xxxxxxxx wrote:

Originally posted by xxxxxxxx

So, should it be in the python SDK in the current form?
Because, as it is now, it shows information that is not accessible directly.

Particle class is used when overriding ObjectData.ModifyParticles(). I think it was wrapped for that purpose. But yes, it should be possible to access directly the particles in an emitter with the Python SDK.