Incorrect lines when applying a stroke to geometry built without initial stroke

[davepagurek]

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build Process
• Unit Testing
• Internalization
• Friendly Errors
• Other (specify if possible)

p5.js version

main branch

Web browser and version

Firefox 114

Operating System

MacOS 12.5.1

Steps to reproduce this

Steps:

1. Set noStroke()
2. Build some geometry using buildGeometry()
3. Set stroke(0)
4. Draw the geometry with model()

You end up with the fill triangles getting strokes rather than the contours passed in between beginShape() and endShape().

I'm not 100% sure if this should be considered a bug or not, but the result feels unexpected enough that I'm leaning towards treating it like one? Fixing this would mean always storing stroke info to p5.Geometry being built even if there is currently no stroke set, since one can add one back later, although this could lower performance when building the geometry. Maybe that's OK though since building geometry is a one-time upfront cost?

Snippet:

let geom

function setup() {
  createCanvas(300, 300, WEBGL);
  
  // Comment this out to make it work
  noStroke()
  geom = buildGeometry(() => {
    beginShape()
    for (let i = 0; i < 10; i++) {
      const angle = i/10 * TWO_PI
      vertex(100*cos(angle), 100*sin(angle))
    }
    beginContour()
    for (let i = 0; i < 10; i++) {
      const angle = -i/10 * TWO_PI
      vertex(20*cos(angle), 20*sin(angle))
    }
    endContour()
    endShape(CLOSE)
  })
}

function draw() {
  background('red')
  fill('white')
  stroke('black')
  model(geom)
}

With noStroke() before buildGeometry():

With a stroke in buildGeometry():

[Artimus100]

hello @davepagurek is this still up to solve!? seems interesting

[davepagurek]

This is still open! I believe it's happening because we don't add strokes in p5.GeometryBuilder here https://github.com/processing/p5.js/blob/main/src/webgl/GeometryBuilder.js#L68 if the user is not drawing with strokes enabled. Later on, if one turns on strokes and a geometry does not yet have any, something is generating edges based on the triangles.

Maybe we need to just add strokes regardless? We should benchmark how much extra runtime cost that adds for large shapes though.

[Artimus100]

@davepagurek sure im on it!!

sorry for being late!!

[davepagurek]

No worries, thanks! I'll assign this to you.

[Artimus100]

@davepagurek again im sorry for being so late but i have a pr please review it!?

-Thank You

[perminder-17]

This issue is resolved by #7287. Thanks everyone for their inputs. :)