Test scene 3

The source

plane{z,0.02

  pigment{leopard
    pigment_map{
      [0 rgb 1]
      [0.4 rgb 1]
      [0.4 rgb 0]
      [1 rgb 0]
    }
  }
  scale .02
  finish{ambient 1}
}

camera{
  location <0,0,-5>
  look_at 0
}

close-up

Without Anti-Aliasing

Perfect

Test I - no strict samples per pixel limit

double size and scaling - 4.00 SPP

Method 1 (old) [+AM1 +A0.05 +R4 +J0] - 4.31 SPP

Method 2 (old) [+AM2 +A0.05 +R3 +J0] - 4.04 SPP

Method 3 (like 2 but mostly using less SPP) [+AM3 +A0.05 +R3 +J0] - 4.04 SPP

Method 4 [+AM4 +A0.05 +R3 +J0] - 3.05 SPP

Method 5 (like 4 but forcing midpoint always traced) [+AM5 +A0.05 +R3 +J0] - 4.95 SPP