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Magnetic field tutorial - last step

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rurik2000
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Hello

I've dropped out of Houdini for a version or two, and am now trying to create an effect as described in the following tutorial
http://pepefx.blogspot.com/2015/08/how-to-create-magnetic-vector-field-in.html [pepefx.blogspot.com]

However I get stuck at the last step where the author suggests randomizing the f@pole attribute to create a more “sun” like magnetic field.
I assume this is done in an attribute wrangle SOP, but I'm not sure what the syntax would be?

Thanks for any pointers
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Enivob
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Here is my interpretation of your request.

I added a switch as the author suggested and scattered points within a sphere.
Then I used an attribute wrangle to create random pole values for each point.
This connects into the existing structure described in the tutorial.

Attachments:
ap_two_pole_magnetic_field.hipnc (91.8 KB)
Screen Shot 2016-01-08 at 1.21.29 PM.png (193.5 KB)

Using Houdini Indie 20.0
Windows 11 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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rurik2000
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Thanks, that is the right interpretation, but to formulate the question more precisely, how do you randomize the pole values?

Thanks!
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Enivob
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To quote an old Chinese chef I worked for “Use you eye”.

The random pole code is posted in the image and in the HIP file I attached.
Using Houdini Indie 20.0
Windows 11 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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rurik2000
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Hmm, I just looked twice and I don't see any attachment…
Am I missing something?

Thanks again
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rurik2000
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Oops, sorry, for some reason that image was taking a long time to load, now I see it!

Thanks
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rurik2000
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I have one more question…I like the way the velocity attribute get mapped to the Cd attribute via the volumetrail SOP. I'd like to modify the way this mapping happens…What is the best way to do that?

When I look at the volumetrail SOP, I don't see a velocity attribute being created, so not sure how I would go about modifying it?

Thanks!
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Enivob
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Try setting your Visualize Velocity Ramp to greyscale. Then add an attribute VOP after the Volume Trail. Dive inside the VOP and add A Ramp parameter and connect Cd from the Globals to the Ramp and then back to the output. Jump up one level and you will have a standard color ramp that you can colorize as you see fit.

Attachments:
Untitled-2.jpg (35.0 KB)
Untitled-1.jpg (108.4 KB)

Using Houdini Indie 20.0
Windows 11 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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