The quick answer is to make a copy of the flight HDA (Houdini Digital Asset) and then modify this custom light to your liking.
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Backing up a bit, every node in Houdini is treated as though it had a tool wrapper and that it itself is a locked digital asset.
Those operators written and compiled from c++ code are pretty much locked down hard and you have to sub-net them in order to build a custom interface on top of.
The quickest way to see which nodes are editable and copy-able HDA's that you can build a new asset on directly is to MMB (MiddleMouseButton) on that operator and inspect the node info. Just look at the “Defined by:” line. If it exists at all, you have an HDA which means you can make a copy and create your own version of that operator.
Here's what an hlight Light node looks like using the Houdini textport and the opinfo command:
/ -> opinfo /obj/hlight
hlight1:
Full Name: /obj/hlight1
Operator type: hlight
Defined by: /Library/Frameworks/Houdini.framework/Versions/12.1.111/Resources/houdini/otls/OPlibObject.otl?Object/hlight
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hlight1 contains 31 SOPs.
Display and Render SOP: switch3
____________________________________________________________________________________________________________________________
No pre-transform.
____________________________________________________________________________________________________________________________
Synchronized with definition
____________________________________________________________________________________________________________________________
Last Cook Time: 0.41 ms
Total Cooks: 1
____________________________________________________________________________________________________________________________
Created Time: 25 Oct 2012 11:42 AM
Modified Time: 25 Oct 2012 11:50 AM
Time Dependent: No
Now it becomes a straightforward task of creating a copy of this asset that you own and modify at will:
- RMB on any flight and choose the “Operator Type Manager” option
> In the Operator Type Manager dialog that pops up, you will see the entry “Object/hlight” node highlighted in the Operator Type Manager.
- RMB on the hlight entry and from the menu, choose the “Copy…” option.
> The Copy Operator Type dialog will pop up with a few options.
- In the Copy Operator Type dialog, put in your own Name Label and point it to a location on disk where to save the .otl library file.
As an example…
> Operator Name: custom_hlight
> Operator Label: Custom Light
> Save to Library: $HOME/houdini12.1/otls
- Press Accept and you are done. You now have your own hlight that you can modify at will.
The only item you can't change later on is the Operator Name. If you do want to change this, you have to make another Copy of this and follow this process again. There are other methods but this works as well as any for now.
Tab add your new light and start customizing it. You have to carry the customizations for the default light around anyway you slice it so what better way than with your own custom Light HDA.
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So an inquiring mind might now ask “just what makes a plain jane Houdini object a light?”
Great question and the answer lies with SOHO (Scripted Output of Houdini Operators) that writes out the ifd/rib/mi scene description file that is fed in to whatever render engine of choice.
Because it's SOHO, it's invariably going to be a pre-defined parameter known to SOHO which we call a Render Property. In this case, on any operator that is to be a light, there is a hidden parameter “Render Property” with name: “light_wrangler”. It is a string parameter and it defaults to “HoudiniLight”. If you have any object that contains this Render Property set accordingly and it has the requisite parameters that define a light (more Render Properties such as light_type and light_color, etc), it will be a light as far as SOHO is concerned. No worries though if you just copy an existing light HDA as it will inherit all this.
To see this, just RMB on any hlight and open the Edit Operator Type Properties and turn on the “Show Invisible Parameters” and do a quick find using “light” as the Filter key word.
