Hello,

When I add more columns and rows to the grid object in the screenshots, the UV noise node acts the same way (same “noise” pattern). Does adding more rows and columns add “more” UVs, or is Houdini simply showing the UV coordinates for every division in the grid and the UVs are already all “there”? I was expecting to turn on “UVW Coords” in the Display options and see the UV coords all jumbled up from the noise, but they are all still in perfect grid formation. Is there a way to visualize the coordinates in jumbled/noisy arrangement?

~Caesar

The grid is having uv's constructed on it and it is the UV creation in SOPs that determines the behaviour. Surely you can create/affect uv's in the shader but it looks like in your example, uv's are constructed in SOPs.


The UV Texture SOP by default will apply uv's to the bounding box of the input geometry. If you make the grid larger or add more divisions, the uv's will still go from 0-1 across the grid, given a proper projection direction.

Increasing or decreasing divisions will have no effect. Just more geometry with uv's calculated by the UV Texture SOP to be even across the surface with no distortion.


All the other UV type SOPs will add uv's to the geometry with specific projection methods. Increasing/decreasing scale of incoming geometry will affect the uv's but as you noticed, increasing or decreasing divisions on the geometry will have no effect as the uv creation type SOPs will simply construct uv's on the changing topology evenly without distortion.


So it is all happening in SOPs.


To see the uv view, just hit the “5” key in the viewport. This allows you to see the uv's calculated as you make changes. Remember to hit “1” to get back to perspective view. Or use the yellow text menus in the upper right of the viewport.


The way attributes are handled in this way is a Houdini cornerstone and is still unique to Houdini. All attributes, just not uv's behave the same way. Add your attributes up or down the chain and they go for the ride, re-computing where necessary in a predictable manner.

Hope that helps.

Thanks Jeff - extremely helpful