[Sidefx-houdini-list] Point Instancing Animation

Agent Xray xray at agentxray.com
Mon Aug 14 11:26:10 EDT 2006

You are right that their _should_ be a direct way to refer to the files. 
As I sated, my suggested method is hacky, at best.

Jeff Willette contributed this useful HDA to the Houdini Exchange that 
will create intermediate geometry:


It caches geometry to disk and reads it in again, doing sub-frame 
blending of like topology. Check it out. You might be able to replace 
the file SOP's in the example I sent you with this HDA in order to get 
inter-frame blending if you can figure out how to properly pass the per 
particle velocity back up to the object you are instancing. How are your 
passing your frame attribute to the instance? I'm curious.


Jaideep Khadilkar wrote:
> HI Agent Xray..
> Thanxx.
> I tried ur method. And it is working fine. Creting objects is cool.. but I still think that thier should be a direct way, to refer to Files. 
> By the way, what u have said in ur last mail, problem of speeding up or down the animation depending on the velocity. I know that I can creat a frame attibute and change it according to my velocity. And I can get variation in the animation. 
> But I didn't get the "frame blending in sop" concept. Can u have a intermediate geometry, between two seperate frames??? Can u explain me how do u do that?
>  ----- iamjaideep80
> Jaideep Khadilkar
> TD, Sciclone Motion Graphics
> Agent Xray <xray at agentxray.com> wrote: 
> Yea, I was looking for some kind of per frame instance attribute but 
> couldn't find it. Seems like the "render from archive" feature only 
> works from Object level.
> The other problem with the method I sent to Jaideep is that it doesn't 
> take velocity into account. In many cases it might be desirable to play 
> the animation faster or slower based on the particle velocity. While 
> it's possible to set up inter-frame geometry blending at the SOP level, 
> I'm not sure how to pass the information from the POP up to the 
> referenced SOP.
> Dan Seddon wrote:
>> Yes - I've don't it exactly this way before, subnets works well if you 
>> have multiple animations too. But, it gets really..... really... 
>> painfully slow when you have a number of sequences. We've mentioned to 
>> sidefx that it would be good to have better sequence handling in this 
>> respect - possibly an attribute that references directly from disk 
>> (something like "instance_archive") or being able to use stamp() 
>> within an object that has been instanced.
>> Dan
>>> Jaideep,
>>> Here's a hacky way to do what you want.
>>> First, bake out the ten frames of geometry from the ROP in the 
>>> "numbers_instanced" object. This is geometry from a font sop with the 
>>> numbers 1 to 10, just for this test.
>>> I'm using an expression in the Instance POP to reference any number 
>>> of geometry objects based on the fit() expression. Each geometry 
>>> object contains a file sop with an animation offset based on the 
>>> opdigit(). You'd could easily generate hundreds of such objects with 
>>> a loop in Hscript, or just copy and paste ever growing numbers of 
>>> them. As long as you base the offset on opdigit(), each one will be 
>>> offset based on the expression you use in the file SOP.
>>> Again, to get this to work on your system, be sure to bake out the 
>>> ten frames of geometry from the ROP in the "numbers_instanced" object.
>>> Cheers,
>>> -=X
>>> Jaideep Khadilkar wrote:
>>>> Hi Doug ...
>>>> Thanx for ur suggestion. But in my case, I have to use 3d Models, 
>>>> sprites won't work, as I need high detail. And fishes are not just 
>>>> travelling tangentioal to the camera, but in any direction.
>>>> Any way,,, thanx.
>>>> ----- iamjaideep80
>>>> Jaideep Khadilkar
>>>> TD, Sciclone Motion Graphics
>>>> Doug Struthers  wrote: Hi Jaideep
>>>> Have you considered the sprite pop?
>>>> I recently used it to make a large (300,000) crowd.  In my case I 
>>>> could use
>>>> a still as a texture but I imagine you could point it at sequence for a
>>>> texture and I think it would be straight forward to have several 
>>>> texture
>>>> sequences and randomize them onto sprites.
>>>> I could watch quite a few sprites in real time on my monitor which 
>>>> helped
>>>> with design and it all rendered very quickly.
>>>> Doug Struthers
>>>> www.dougstruthers.com
>>>>> -----Original Message-----
>>>>> From: sidefx-houdini-list-bounces at sidefx.com 
>>>>> [mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of 
>>>>> Jaideep Khadilkar
>>>>> Sent: Saturday, August 12, 2006 12:50 AM
>>>>> To: Houdini Mail List
>>>>> Subject: [Sidefx-houdini-list] Point Instancing Animation
>>>>> Hi Everybody...
>>>>> Need ur Help, again.. I am trying to make a school of fish. So I am 
>>>>> trying to use particles and Fish animation instanced on them.  If I 
>>>>> make Fish animation as a single object and instance it, what I will 
>>>>> have is the same animation on every point without any offset. I 
>>>>> tried Copy sop but it is too heavy. So instancing is must. I want 
>>>>> to have a time offset, to break similarity. How can I do that? 
>>>>> Suppose I write out my animation as a sequence of bgeo files, how 
>>>>> can i make each point to load different bgeo file?? How can I pass 
>>>>> this attribute?????? I know it can be done by creating different 
>>>>> objects for different frame number and cycle thru them using 
>>>>> instance attribute in Point Sop. But I don't want to do that cause 
>>>>> my animation is 100 frame long. So that way, I have to creat 100 
>>>>> different objects. Is there any simple method to refere to a file 
>>>>> insted of object in instance attribute????
>>>>> ----- iamjaideep80
>>>>> Jaideep Khadilkar
>>>>> TD, Sciclone Motion Graphics

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