[Sidefx-houdini-list] DOPs Impact question

Graham Thompson captainhammy at gmail.com
Wed Jan 12 19:33:39 EST 2011


Strange, the help works for me no problem.  Configurations are just
the term I used for different setups and masking.  For example you can
just set it to 1 and then it uses * for masks so it will get every
object that impacts against every other one.  If you want specific
filtering then you can add more multiparm instances and use a
"configuration" to specify what objects more precisely.  Here's the
text of the help card:


DOP Impact Points surface node
Generates points based on Impact record data from DOP objects.

This operation creates points at the location of impacts of DOP
objects. These points can contain useful data about the collision as
well as be filtered based on object ids and collision impulse.

Parameters
DOP Network	
The DOP Network to extract the impact information from.

Normal	
The direction of the impact at the point of impact.

Impulse	
The intensity of the impact.

Source ID	
The object id of the object that is impacting.

Other Object ID	
The object id of the object that is being collided against.

Number of Configurations
The number of individual configurations to generate points.

Enable Configureation n	
Controls whether the node uses this line. This can be useful if you
only want to temporarily disable a merge instead of removing it
completely.

Object Mask	
Specifies the objects within the DOP Network to extract the impacts from.

Impact Mask	
Specifies the objects which the objects in the Object Mask will
generate impact points for.

Impulse Threshold	
Specifies the minimum impulse value to create impact points. This
setting allows for the trimming of impacts points once an object has
decreased speed or come to rest.

On Wed, Jan 12, 2011 at 4:16 PM, Craig Hoffman <craigleehoffman at aol.com> wrote:
>
>
>
>  That otl rocks!  Thanks so much!
>
> The Odforce write-up mentions the help card, but that doesn't seem to work for me (I got the last one from the thread).  What exactly is "Number of Configurations?
>
> Thanks,
> Craig
>
>
>
>
>
>
> -----Original Message-----
> From: Graham Thompson <captainhammy at gmail.com>
> To: sidefx-houdini-list <sidefx-houdini-list at sidefx.com>
> Sent: Wed, Jan 12, 2011 2:32 pm
> Subject: Re: [Sidefx-houdini-list] DOPs Impact question
>
>
> This is all really as I would expect it.  Most if not all of the time
>
> your impacts will occur during sub frames.  Depending on your objects
>
> velocity and the amount of substepping and such the simulation might
>
> not recognize that your objects are impacting the ground until they
>
> have part way through, which is why your impact points appear below
>
> the ground plane.  This also explains why you can have a large number
>
> of impact points as a point is generated at each impact during each
>
> subframe.  Looking at the time field of the data can show what happens
>
> during each step.  By increasing the number of minimum substeps you
>
> can get around this problem by increasing the accuracy of the
>
> collisions so it detects the impact right away, though this will
>
> introduce longer sim times and might not be ideal if your sim is
>
> already looking good.  An alternative would be to use a Ray SOP to ray
>
> the points up to the ground plane where you want them.
>
>
>
> As for the data showing up after the impact actually occurred, well
>
> that is related to what I just mentioned.  Your impact occurs during
>
> say frame 21.765342 but since you are using integer frames you can not
>
> really expect to see anything until the next whole number frame in
>
> which case the simulation has advanced and your object probably isn't
>
> impacting anymore.
>
>
>
> Finally, your source object isn't actually a DOP object.  It is a
>
> digital asset that is creating a bunch of data, in the case of the
>
> glue object it is creating a bunch of objects which are then simulated
>
> and receive impact data as they hit individually.  As far as the
>
> simulation engine is concerned there is no "sphereObject1" in your
>
> actually simulation you could attach the data to. As for getting the
>
> data from all your piece objects usually people will use a SOP setup
>
> with some copy + stamping using dopnumrecords and dopfield to get at
>
> the data for each record or each object.  Here is a scripting solution
>
> I've posted a couple times on odforce that dramatically simplifies
>
> this and even lets you attach some attributes as well.
>
>
>
> http://forums.odforce.net/index.php?/topic/11774-python-retreiving-simulation-impact-points/
>
>
>
>
>
> On Wed, Jan 12, 2011 at 12:40 PM, Craig Hoffman <craigleehoffman at aol.com> wrote:
>
>>
>
>>
>
>>
>
>>  Hi guys,
>
>>
>
>> I am doing a DOPs simulation and getting the Impact data out to drive particle
>
> systems where impacts happen and am having some issues.
>
>>
>
>> The DOPs sim looks really accurate- no interpenetrations or anything, but the
>
> "Impact" positions coming out of DOPs aren' exactly where I would expect them to
>
> be.  Some are a fair bit below the groundPlane collision plane (although others
>
> are pretty close).  Is there a way to get more accurate Impact data since the
>
> actual simulation seems pretty accurate?  Also, they seem to show up a frame
>
> after I would expect them to.  Is "Impact" data generated for the frame after a
>
> collision is detected?
>
>>
>
>> Also, I am using a Glue Object, so the Impact Data I want shows up on
>
> "piece1", "piece2", etc. and not on the source object "sphereObject1".  Is there
>
> some way to get all the Impact data from the entire simulation rather than
>
> having to collect it for each piece at a time using expressions like
>
> "dopnumrecords" and "dopfield" (which don't take wildcards).
>
>>
>
>> Thanks for any help.
>
>> Craig
>
>>
>
>>
>
>>
>
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>
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