Softimage|XSI to SideFX Houdini

Forum for users who have migrated or are migrating to Houdini
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owei
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Softimage|XSI to SideFX Houdini

Post by owei » 10 Oct 2016, 14:22

Hey there!

As there is some discussion on the soft list about this, I´ll start a specific thread where people can add their knowledge on transfer Softimage knowledge/workflows over to Houdini. Maybe start with some explanation acronyms (Chris Marshall on the list asked about) that sound pretty cryptic at first. I´ll try to find some similarities to Softimage:

BSDF = "bidirectional scattering distribution function"...controls how light reflects off a surface
PBR = Physically based rendering
VEX = Vector Expressions ..the internal Houdini Language, so to say
VOP = VEX Operators ..some ICE like subnetworks, where you can manipulate all kinds of fetched data
SOP = Surface Operators ..means operators, that deal with all kinds of surfaces (poylgons, nurbs etc.) and manipulates them
VOP SOP = Vector Operators - Surface Operators.. networks that allows to work on a surface in a node based way like mentioned in the VOP
SHOP = Shader Operators ..a network where you can build and manipulate data for shading (render tree..)
ROP = Render Operator ..operators which deal with all kinds of rendering such as image calculation but also caching (geo or points etc.) stuff to disk
DOP = Dynamic Operators ..subnets that contains dynamic stuff like all kind of simulation (RBDs, Cloth, Particles, Flips and so on..)
AutoDOPNetwork = Automatically generated Dynamic Operators Network
CHOP = Channel Operators ..basically everything that has to do with fcurves and animation and stuff..
POPObject = Particle Operators ..a node that creates and manipulates particles
HDA = Houdini Digial Asset ..one way to store and share ready to use networks and import them into Houdini. A little like a mixture of an "emdl" and "ICE compound(s)" in Softimage
COP = Compositing Operators ..a compositing network inside of Houdini

Please correct me and/or add stuff ;)

cheers,
oli

nodeway

Re: Softimage|XSI to SideFX Houdini

Post by nodeway » 10 Oct 2016, 19:00

SOP, ROP, DOP, SHOP, COP, CHOP, VOP... - those are not operators, but context names. Operator can be of some context type, or actually can be executed in some context.
Context is a path in HIP file. You can open HIP file with, for example, 7-ZIP and look inside. You will see directories with scripts. Those directories will correspond to the context you defined in your HIP file. Scripts in those directories tell Houdini what is should do.
That's a bigger topic.

HDA, OTL - that's a collection of files (again), that is packed and describe what and how some things should be done. You can unpack (and pack too) such digital asset and look what's inside of each file (hou.hda.expandToDirectory() and hou.hda.collapseFromDirectory() in python). This allows you to even hack (or fix) some things by modyfing those scripts by hand or by some other scripts. You can, for example, replace UI file with another one, assuming that you will keep all the parameter names exactly the same.

Why would you want to do this?

For example, Houdini engine loads asset into multiple apps. Some apps supports more UI tricks than other, so to make it easier to look at it in all apps, you could generate multiple versions of the UI file, work in Houdini with all UI tricks, and export asset in multiple versions, by automaticaly expanding it, replacing UI file, packing it back. And you have the same asset in each, but with different UI that supports better app in which it's loaded.

AutoDOPNetwork - it's just a name. Scripted name. It could be also named AutoDicks. They (SESI) just decided that it's a good name for networks generated by scripts when you run shelf tools.

Thats my two cents :)

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Hirazi Blue
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"Get data" into vop-network?

Post by Hirazi Blue » 04 Jan 2017, 09:41

I am having a hard time figuring out how to "get data" into a vop-network. I want to access the local primitive variable "NVTX" in my vop-network, but I have no idea how to set it up correctly. What node would I have to use and what settings and connections would be necessary?
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owei
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Re: "Get data" into vop-network?

Post by owei » 04 Jan 2017, 09:47

Use the "Bind" node. If you want to export to a specific attribute, use the "Bind Export"...
By the way, I startet a "XSI to Houdini" thread some time ago..maybe we can put all these stuff in there?

cheers,
oli

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Hirazi Blue
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Re: Softimage|XSI to SideFX Houdini

Post by Hirazi Blue » 04 Jan 2017, 10:22

Thanks. :ymhug:
Good idea, I merged my thread with yours and promoted it to "sticky" status...
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Re: Softimage|XSI to SideFX Houdini

Post by Hirazi Blue » 04 Jan 2017, 10:40

I just tried it using the "bind" node, but it still doesn't get me the correct value into the vop-network. The output of the node always seems to equal the default value set.

As you can see, I am trying to color the primitives that only have three neighbors...
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owei
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Re: Softimage|XSI to SideFX Houdini

Post by owei » 04 Jan 2017, 10:49

I´m no an expert, still learning, so, can you post the scene?
You can also check the "geometry spreadsheet" and check, if the values are there.

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Hirazi Blue
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Re: Softimage|XSI to SideFX Houdini

Post by Hirazi Blue » 04 Jan 2017, 11:03

I am currently using the Appentice version, so posting a scene wouldn't help I guess...
But here it is...

The "NVTX" variable doesn't show up in the "Geometry Spreadsheet".
screen2.jpg
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owei
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Re: Softimage|XSI to SideFX Houdini

Post by owei » 04 Jan 2017, 11:10

No problem..you can post the scene. Scenefiles can be opended by every version, they just "turn" Houdini in the version the scene file comes from..except for the full commercial version.

Beside that, you will have to make sure, you are looking to the correct context in your spreadsheet. Now you are looking at "point" context. The small icons the upper left give the context. Just hover over them with the mouse.

cheers

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Hirazi Blue
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Re: Softimage|XSI to SideFX Houdini

Post by Hirazi Blue » 04 Jan 2017, 11:18

Okay... Now the NVTX shows up, but strangely is set to 0 on all primitives...
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owei
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Re: Softimage|XSI to SideFX Houdini

Post by owei » 04 Jan 2017, 11:51

OK. The attribute shows up, as it gets generated within the bind node. It does not exist prior to that. So, NVTX seems to be local variable used by certain nodes, as the vertext node. Currently no idea, how to transfer the local value to a global attribute, so you can access it via VOPs..I have to investigate ;)

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Re: Softimage|XSI to SideFX Houdini

Post by Hirazi Blue » 04 Jan 2017, 11:56

Thanks!
So it's not just me... #:-s
Keep me updated, please...
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owei
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Re: Softimage|XSI to SideFX Houdini

Post by owei » 04 Jan 2017, 12:23

OK..pretty easy.
Put an "Attribute create" node after your model node.
Name the Attribute "Number" or what ever.
Set Class to "Primitive", Type to "Integer"
At Value type "$NVTX"
Now refer to the "Number" attribute in the VOP via the Bind node..done ;)
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Hirazi Blue
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Re: Softimage|XSI to SideFX Houdini

Post by Hirazi Blue » 04 Jan 2017, 13:41

Great. Thanks a lot! ;)
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NNois
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Re: Softimage|XSI to SideFX Houdini

Post by NNois » 01 Mar 2017, 00:22

the fastest is by using the primitive wrangle and type in

Code: Select all

@myattribute = @numvtx;
this will create an attribute named myattribute filled with the number of vertex

You can do the same with a primitive VOP
then wirering the numvtx parameter to a bindexport. Your attribute will show up too

for the story as VOP is an GUI for VEX if you "view VEX code" the code will look like the VEX code line posted here

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Re: Softimage|XSI to SideFX Houdini

Post by NNois » 23 Mar 2018, 23:40

I think this on deserves his place here !
(as seen on the si-list)