xmax tree sample

Author: chrisws

graphics 4/xmax_tree.bas

@@ -0,0 +1,79 @@
+rem Welcome to SmallBASIC
+rem see https://github.com/anvaka/atree
+nmax = 19
+xScale = 6
+zScale = 2.5
+yScale = 16
+startFrom = 0
+dz = 400
+
+redSpiralShadow  = createSpiral(rgb(0x66,0,0), rgb(0x33,0,0), true, 1.01)
+redSpiral        = createSpiral(rgb(0xff,0,0), rgb(0x44,0,0), true, 1)
+cyanSpiralShadow = createSpiral(rgb(0,0x33,0), 0, false, 1.01)
+cyanSpiral       = createSpiral(rgb(0,0xff,0xcc), rgb(0, 0x56, 0x33), false, 1)
+
+while 1
+  cls
+  renderFrame() 
+  if (startFrom > 1) then
+    startFrom = 0
+  else
+    startFrom += 0.1
+  endif
+  showpage
+  delay 30
+wend
+
+sub renderFrame()
+  xScale *= 0.93
+  forEachStep(redSpiralShadow)
+  forEachStep(cyanSpiralShadow)
+  xScale /= 0.93 
+  forEachStep(redSpiral)
+  forEachStep(cyanSpiral)
+end
+
+sub forEachStep(spiral)
+  local i = -startFrom
+  while i < nmax + startFrom
+    if (i >= 0 && i <= nmax) then
+      spiral.show(i)
+    endif
+    i += 0.08
+  wend
+end
+
+func createSpiral(foreground, background, isLeft, yLocalScale)
+  local spiral
+  spiral.sign = iff(isLeft, -1, 1)
+  spiral.yLocalScale = iff(LocalScale > 0, yLocalScale, 1)
+
+  if isLeft == 0 then
+    spiral.background = foreground 
+    spiral.foreground = background 
+  else
+    spiral.background = background
+    spiral.foreground = foreground
+  endif
+
+  func getX(i, z, sign)
+    return sign * i * cos(i) * z * xScale + 255 
+  end
+
+  func getY(i, z)
+    return i * z * yScale + 50 
+  end
+  
+  sub show(i)
+    local zoff = i * sin(i)
+    local z = dz / (dz - self.sign * zoff * zScale)
+    local x = getX(i, z, self.sign)
+    local y = getY(i * self.yLocalScale, z)
+    local c = iff(zoff + self.sign * PI / 4 < 0, self.foreground, self.background)
+    line x, y, getX(i + 0.03, z, self.sign), getY((i + 0.01) * self.yLocalScale, z), c
+  end
+
+  spiral.show = @show
+  return spiral
+end
+