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COPS & VOPS

  • Writer: Sammy Lyu
    Sammy Lyu
  • Aug 5, 2025
  • 2 min read

Updated: Nov 21, 2025

This section focuses on the attribute VOPS in Houdini for things like noise generation and COPERNICUS.


As of writing, my Houdini version is 20.5.614





MULTIPLY


You can use the “MULTIPLY” function to combine noises such as WORLEY and TURBULENT noises, instead of just layering them on top of each other using the ADD function. iThis creates SMOOTHER EDGES when adding noise to surfaces in COPS & VOPS.



RANDOM & SEEDS


You can use the RANDOM function on the SEED input of a particular noise to create slightly varying noises for each surface of the geometry you are working on.



VDB POINT SCATTER


Instead of using a points from volume, you can convert the geometry to a Fog VDB with a density attribute and scatter point on that instead; this method gives more control to the points being scattered than a points from volume SOP.


  • This cannot be done on the distance VDB surface attribute since that only deals with the surface of the geometry and not the volume inside.


VOLUME VOP TO CREATE NOISE FOR DENSITY ATTRIBUTES


When you have a VDB volume with a density attribute, you can use the VOLUME VOP, to add noises to the pattern of the density in the same way turbulent noise can be added to a texture in COPS.



PROMOTING PARAMETERS FROM VOP TO TOP LEVEL


On a VOP node, right click, select VEX/VOP options, and select CREATE INPUT PARAMETERS. This creates a reference of the attributes and parameters of a VOP node, like the frequency of a turbulent noise, on the SOP level nodes.



ATTRIBUTE NOISE LAYER TO ADD NOISE


Using the attribute noise sop, you can quickly ADD simple noises to geometries and particles without needing to dive into the more complicated attribute vop.



USING ATTRIBUTE VOP TO ADD VELOCITIES


The attribute vop is not only for NOISES, it can also add velocity to a simulation in a simple and art-directable way.



IMPORT POINT ATTRIBUTE TO SHAPE VELOCITIES


The import point attribute vop allows us to bring in geometry point POSITION data (P), and use that data to affect and shape how the velocity is generated, this example below shows the setup used to achieve this:


In this setup, I ASSEMBLED the geometry, transformed it to a different shape, and imported the points into the attribute vop. Then I subtracted the new shape with the old shape and used that point data to affect the shape of the velocity. The multiply function is there to affect the INTENSITY of the velocity.



MATCHING COLOUR TO AN ATTRIBUTE USING POINT VOPS You can use a POINT VOP to map colours to a certain attribute instead of using the color SOP. This is done with the COLOR MIX and BIND nodes as follows:

In this example, we map the temperature attribute to the colours selected in the COLORMIX node, the selected colours in this case were black and white, so the geometry will be more black at the points where temperature is higher.


 
 
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