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Topology Help: How to Split Faces to Fix Choppy Lighting?

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How should I split the faces here? The lighting doesn't flow smoothly on this surface.

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  • zylan
  • Quasar
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    Quasar polycounter lvl 20
    I'm not seeing any issues  :/
  • sacboi
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    sacboi grand marshal polycounter
    Instead of solid mode with phong shading - I'd preview whatever 'lighting' artifact you think may have occurred in either lookdev/material or cycles viewport lit with a basic 3 point setup which would enable people too offer more effective feedback, if applicable?
  • zylan

    Sure, please take a look at this. It illustrates the problem much better, the earlier image wasn't clear enough.
  • sacboi
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    sacboi grand marshal polycounter
    Ok an N-pole shading error - (a vertex where 5 or more edges meet) which forces Blender to average face normals across different angles, causing dark spots or "pinching" artifacts when using smooth shading.

    And here's a few options that may resolve the problem

    1. To fix the Normals and Smoothing often, shading artifacts were caused by broken or locked vertex normals. 

    • Recalculate Normals: Go to Edit Mode, press A to select everything, and press Shift + N to recalculate normals on the outside.
    • Clear Custom Normals: If your model was imported (e.g., from CAD) or had complex modifiers applied, it might have baked normal data. Go to Object Data PropertiesGeometry Data and click Clear Custom Split Normals Data.
    • Adjust Auto Smooth: If Auto-Smooth is toggled on, tweak the angle slider. Alternatively, setting the mesh to Shade Flat completely removes the shading interpolation. 

    2. Use a "Weighted Normal" Modifier

    If the N-pole is on a curved surface that needs to look smooth, Blender's Weighted Normal modifier can force the surrounding geometry to respect flat edges rather than stretching shadows.
    • Go to the Modifiers tab and add a Weighted Normal modifier.
    • Check the Keep Sharp box.
    • (Optional) Increase the Weight to adjust the blending. 

    3. Adjust Your Topology (Edge Flow)

    The long-term solution is to move poles away from high-visibility, curved, or deforming areas. 
    • Slide the Pole: If you can't delete the pole, use the Edge Slide tool (GG) to move it to a flat area of the mesh where the shading interpolation won't be as noticeable.
    • Quads and Loops: Add supporting edge loops to tighten the geometry around the pole. This prevents the lighting from stretching too far across large, irregular faces. 

    4. Data Transfer (For Complex Shapes)

    For extreme cases where the geometry is complex and you cannot fix the N-poles manually (such as after a Boolean operation), you can project the normals from a perfectly clean object onto your error-prone mesh. 
    • Duplicate your object and remove the N-poles or problematic cutouts so the base shape is perfectly smooth.
    • On the original, error-prone mesh, add a Data Transfer modifier.
    • Set the duplicated mesh as the Source Object, enable Face Corner DataCustom Normals, and set the mapping to Nearest Face Interpolated. 
  • Eric Chadwick
    Despite the possible fixes, it's best not to worry about minor shading issues like this early on in the modeling process. Usually these little things are not at all noticeable in the materialized surface, and totally not worth the effort to fix at this point. Complete the texturing and import into your renderer and apply the lighting/cameras, THEN re-examine this and see if it's still there.

    Also important to note that models typically undergo multiple revisions before final, so if you do tiny little tweaks to vertex normals, that work is probably going to be lost and have to be re-done a few times.
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