Houdini – TOP Wedge

Created On23 June 2020

Last Updated On23 June 2020

There is 2 different ways to use Wedge in TOP context.

The push Method is similar to the used with the ROP Wedge. You will set the values in the Wedge Node directly.

With The pull Method you will create attributes (@attribute_example) that you can used later to change the values of your setup. The values will be driven by PDG.

Pull references are very convenient and flexible. However, it does require using TOPs-specific expressions, and it may not be appropriate if you want to use your setup/shaders without TOPs.

SideFx Documentation

Push Method

With this method you will pick-up directly the name of the parameter you want to change in the TOP Wedge Node.

Check the box next to Target Parameter
Go and search for the parameter you want to change (you have access to almost anything)
The Attribute Name will be filled-in automatically. It must have the same name than your parameter. You can’t change it or you will have an error.
Change you range and/or change the wedge type (you can have a range like in the ROP Wedge, but you can also choose a specific value, or set a list of values also attribute type)
Choose how much values you want in Wedge Count

In our case this will generate a wedgeattrib named s_noisefreq1 to get access to the value, you just have to put a @ in front of its name.

To see this, middle-click on a point/task of your TOP wedge

(you need to cook the node to see this with SHIFT+V)

We can use this value to write geometry files or our rendered images.
To do so, you will need to add ` before and after the name: `@s_noisefreq1`
For me, it has more sense than the `@wedgeindex` that we can find in the documentation.

Pull Method

With this method you will define in the TOP Wedge Node, an attribute with a name and values.

Then you will go into your setup and replace the value of the parameter with the name of your @attribute.

Set an Attribute Name that you will use in your setup later
Change you range and/or change the wedge type (you can have a range like in the ROP Wedge, but you can also choose a specific value, or set a list of values also attribute type)
Choose how much values you want in Wedge Count

Go back to your setup / shader, go to your parameter and enter the name of your attribute with @ in front (here @freqPDG)

Shader – Define Parameter Attribute with Wedge PULL Method

We can also use this value to write geometry files or our rendered images.
To do so, you will need to add ` before and after the name: `@freqPDG` to have the value and you can some text before to help the reading.
Example: enter freq_`@freqPDG`to have the context and value in the filename

How to proceed for a rendering

After adding your wedge(s)
Add a node ropmantra
Define your rendering parameters like a normal Mantra Node
Change from single frame to frame range
The single frame doesn’t take into account the current frame
Change the Output picture to read your wedge parameters like: $HIP/render/$OS.freq_`@freqPDG`.bias_`@biasPDG`.$F4.exr
Press SHIFT+V to cook your mantra node

How to proceed for a geometry

Go back to your setup
At the end of your setup where you would have put a filecache drop a Null and rename it OUT
Go back to your Topnet
Add a node ropgeometry after you Wedge(s)