OpenGL strokeCap(ROUND) and strokeJoin should account for scale when computing the number of arc points

Created by: scudly

The default renderer very smoothly supports zooming in on ROUND line endcaps and joins while maintaining their roundness. P2D and P3D, however, assume that any strokeWeight less than one won't have visible endcaps even when the scale factor blows them up to many pixels in size.

The following code runs fine with s = 600, i.e., no scaling. Change to s = 1, however, and the endcaps and joins disappear. Remove the P2D and both cases will stay smooth.

float s = 600;
void setup() {
  size( 600, 600, P2D );
  noFill();
  scale( height/s );
  strokeWeight( 0.2*s );
  point( 0.3*s, 0.3*s );
  strokeJoin( ROUND );
  beginShape();
  vertex( 0.6*s, 0.2*s );
  vertex( 0.8*s, 0.8*s );
  vertex( 0.2*s, 0.6*s );
  endShape();
}

首先使用 P2D 在 s = 600 和 s = 1 时运行提供的 sketch，然后在不使用 P2D 的情况下进行比较。跟踪 P2D 和 P3D 对 ROUND 描边端点和连接处的处理，重点关注弧线点数如何使用 strokeWeight 和 scale。完成标准是缩小后的描边仍保留可见且平滑的圆形端点和连接处。