Weird PCG Difference node behavior - help wanted!

Development World Creation
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HI,

Working extensively with the PCG Difference node has been quite frustrating. I’m wondering if there’s a way to resolve this issue.

I frequently perform Difference operations and have noticed that the Difference node does not behave consistently. I intend to use it as a subtraction node, which should leave only those source nodes that don’t exist in the Difference. Occasionally, this works as expected, but more often than not, it does not. The density parameter of the points is significantly impacted, making the results unpredictable after a series of operations.

I’ve discovered a trick to “refresh” point density using the Density Remap node right after the Difference one. However, this doesn’t always succeed, often leaving strange empty spots in my design where a mesh should be generated.

I’ve watched many tutorials where this problem didn’t appear. I’m using Unreal Engine 5.4.2—could this be related to bugs in this version?

Any help would be greatly appreciated.

Best,
Miki

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image1134×596 144 KB

That is the difference

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That is the Source to substract from

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Result!
I tried all the options for Difference Node regarding density function. Didn’t help!

2 Likes
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Problem solved!

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Hello,
Thanks for sharing your experience with the PCG Difference node. It’s indeed frustrating when a core tool behaves inconsistently.
Potential Causes for Inconsistent Behavior:

  1. Data Precision Issues:
    Floating-point inaccuracies can lead to unexpected results when comparing points. Consider using a snapping or quantization node before the Difference to improve precision.
  2. Point Density Variations:
    Significant differences in point density between input sets can affect the Difference node’s behavior. Experiment with different sampling methods or point density adjustments.
  3. Topology Issues: HPInstantInk
    If the input data has complex topologies (e.g., holes, overlaps), the Difference node might produce unexpected results. Simplify the input data or use additional nodes to preprocess the geometry.
  4. PCG Node Configuration:
    Review the Difference node’s settings, such as tolerance values and distance checks. Experiment with different configurations to find optimal results.
  5. Unreal Engine Bug:
    While less likely, there’s a possibility of a bug in the PCG system. Check for known issues or updates.
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How did you solve this problem? I am having a similar issue, and I can’t figure it out!

1 Like
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This thread is the top result when you’re searching for PCG difference node problems and it’s infuriating, with the “i fixed it myself!” followed up with the ChatGPT nonsense spam reply. It’s almost beautiful in how unhelpful it is