Instance Geo on particles

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Instance Geo on particles

Postby derekhanz » Thu Jul 20, 2017 3:56 pm

derekhanz Thu Jul 20, 2017 3:56 pm
I'm using the latest build of Octane for Houdini.

I'm trying to render massive amounts of particles as custom geo.

By packing and instancing the geo in a copytopoints node it should be quick to load and render, like Octane Scatter in C4D

The load time takes far too long. What am I doing incorrectly?


Thanks
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Re: Instance Geo on particles

Postby derekhanz » Thu Jul 20, 2017 4:37 pm

derekhanz Thu Jul 20, 2017 4:37 pm
Followed the manual online and figured it out.

Attribute create, called it Instance, made it a string and pointed to the geo.

I thought that the latest version of Octane would do this automatically using copytopoint node, without having to use an attribute create?

thanks
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Re: Instance Geo on particles

Postby juanjgon » Thu Jul 20, 2017 4:45 pm

juanjgon Thu Jul 20, 2017 4:45 pm
Hi,

Nope, sorry. The Copy SOP is only understood as an instancing tool by Mantra at render time. From the scene point of view, at extraction time, this node is seen by Octane like a node that builds physical copies of the object, not instances.

As you have found, you need to use the "instance" point attribute or the Instance OBJ node to render real Octane instances of your master object.

Thanks,
-Juanjo
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Re: Instance Geo on particles

Postby hellochristhompson » Thu Jul 27, 2017 2:19 am

hellochristhompson Thu Jul 27, 2017 2:19 am
Thanks, juanjgon. This info was super useful.

I'm trying to push it a little further and color each instance based upon the Cd point attribute. I know this wasn't available in the past but I'm hoping this is now possible? Is this wishful thinking?

Having the particle "render as sphere" option is super useful but it'd be great if we could use user defined geo while including the Color/Alpha attribute.
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Re: Instance Geo on particles

Postby juanjgon » Thu Jul 27, 2017 8:17 am

juanjgon Thu Jul 27, 2017 8:17 am
Nope, sorry. This is not possible yet. You have a random color node to configure random shading parameters in the instances, but the support of the Cd attribute is not possible. I hope to see this feature soon in the Octane core, once we have the OSL feature in place to write custom shaders to retrieve the custom attributes at render time.

Thanks,
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Re: Instance Geo on particles

Postby TravellerInTime88 » Tue Sep 17, 2019 9:47 am

TravellerInTime88 Tue Sep 17, 2019 9:47 am
Hi!

I know this is an old post, but I've been trying to replicate the instancing method as described by both @derekhanz and @juanjgon, but to no avail.. I have created an attribute called "instance", set it to string and then on the string parameter, I reference my object as such: "../objtoinstanciate_1". When I hit the IPR button though, I get an error stating that the instance node is referencing a not available object. Clearly I am doing something wrong in the declaration, but what? What am I missing?

Also, is this method quicker than the copy to points node? Because right now with copy to points, rendering in octane per frame is about a minute, and the loading of the scene is almost the same! :shock:

Thank you very much for your time,
G.
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Re: Instance Geo on particles

Postby juanjgon » Tue Sep 17, 2019 5:30 pm

juanjgon Tue Sep 17, 2019 5:30 pm
Hi,

Can you please try with the absolute path or with "../../objtoinstanciate_1"? In any case, probably should be easy support also the "../objtoinstanciate_1" path types.

About your second question, nope, it is not the same. Currently, the copy sop final geo is not extracted by the Octane plugin as instances. The full final geo is expanded without instancing, so the extraction and render time can be indeed slower in complex objects. You need to use the instance attribute or the Instance OBJ node to instance objects.

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Re: Instance Geo on particles

Postby TravellerInTime88 » Thu Sep 19, 2019 10:01 am

TravellerInTime88 Thu Sep 19, 2019 10:01 am
Yeah, I actually figured it out the other day - thank you! I also did some tests with the instance and indeed - it is actually quite faster this way, you are right!

And thanks for taking the time to reply,
G.
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Re: Instance Geo on particles

Postby efxlab » Tue Feb 04, 2020 7:23 am

efxlab Tue Feb 04, 2020 7:23 am
Is it possible now with 2020 to retrieve attribute from packed instance in houdini ?
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Re: Instance Geo on particles

Postby juanjgon » Tue Feb 04, 2020 12:00 pm

juanjgon Tue Feb 04, 2020 12:00 pm
efxlab wrote:Is it possible now with 2020 to retrieve attribute from packed instance in houdini ?


Octane doesn't support user attributes in the instances yet (Octane 2020 supports them in the meshes, curves, and particles), but in any case, the packed instances are not extracted as Octane instances, they are expanded to the full geo, so well, if they have any embedded attribute, it should be available for Octane.

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