Flat rendering on PGraphics3D of PShapes created from PGraphics2D

Created by: onimatrix

Calling createShape() directly will use the Applet renderer.
If this renderer is set to be of type P2D, the resulting shape seems to ignore any z value set to it's vertices.
I'm guessing that this shape contains some optimizations aimed at 2D rendering.

There should be a warning when using this kind of "flat" PShape on a P3D renderer.
Maybe even a different PShape class to make it foolproof.
Also, it would be great if 3D PShapes could be created without needing to reference a PGraphics3D that is in the "draw state".

Here's a piece of code to replicate the issue:

PGraphics g3D;
PShape shape;

void setup()
{
  size(800, 600, P2D);
  g3D = createGraphics(width, height, P3D);
  
  //g3D.beginDraw(); // uncomment to fix flatness
    shape = createShape(); // change to g3D.createShape(); to fix flatness
  //g3D.endDraw(); // uncomment to fix flatness

  shape.beginShape(LINE_STRIP);
    shape.vertex(0, 0, 0);
    shape.vertex(200, 0, 0);
    shape.vertex(200, 0, 200);
  shape.endShape(CLOSE);
}

void draw()
{
  g3D.beginDraw();
    g3D.background(255);
    g3D.translate(width / 2, height / 3, 0);
    g3D.rotateY(((frameCount % 400) / 400.0f) * TWO_PI);
    g3D.shape(shape);
  g3D.endDraw();
  
  image(g3D, 0, 0, width, height);
}

• Processing version: 4.2
• Operating System and OS version: Windows 10

Inizia eseguendo lo sketch fornito e confronta createShape() con g3D.createShape(), incluso il caso beginDraw(). Segui i punti di ingresso createShape(), PGraphics2D, PGraphics3D e PShape per determinare dove viene selezionata la forma piatta; il lavoro è completato quando il caso d’uso P3D viene gestito esplicitamente, con l’avviso richiesto o con un percorso chiaramente supportato per la creazione di una forma 3D.