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2019/sketch_190630a/sketch_190630a.pyde

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+# Alexandre B A Villares - https://abav.lugaralgum.com/sketch-a-day
+# More combinatorics of triangles in grids based on sektch_190602a
+# Lerp to make intermediary triangles
+
+from itertools import product, combinations
+
+def setup():
+    global two_triangle_combos, triangles, space, border
+    size(200, 200, P3D)
+    border = 50
+    space = width - 2 * border
+    smooth(8)
+    blendMode(MULTIPLY)    
+    strokeJoin(ROUND)
+    # points on a 3x3 grid
+    grid = product((-1, 0, 1), repeat=2)
+    # all 3-point combinations on the grid
+    points = combinations(grid, 3)
+    # identify triangles (discard colinear point triples)
+    triangles = []
+    for p in points:
+        area = (p[1][0] * (p[2][1] - p[0][1]) +
+                p[2][0] * (p[0][1] - p[1][1]) +
+                p[0][0] * (p[1][1] - p[2][1]))
+        if area != 0:
+            triangles.append(p)
+    println("Number of possible triangles: {}"
+            .format(len(triangles)))
+    # calculate 2-triangle combinations
+    two_triangle_combos = list(combinations(triangles, 2))
+    println("Number of 2-triangle combinations: {}"
+            .format(len(two_triangle_combos)))
+
+def draw():
+    background(240)
+    ortho()
+    translate(width / 2, height / 2)
+    rotateY(radians(frameCount))
+    noFill()
+    i = (frameCount % len(two_triangle_combos)) // 90
+    draw_combo(two_triangle_combos[i])
+
+def draw_combo(combo):
+    strokeWeight(border / 10)
+    noFill()
+    siz = space * .5 # .35
+    triangles = (combo[0],
+           lerp_poly(combo[0], combo[1], 0.33),
+           lerp_poly(combo[0], combo[1], 0.66),
+           combo[1])
+    for i, t in enumerate(triangles):
+        # colors for each of the triangles
+        colors = (color(200, 100, 0),
+                  color(133, 100, 66),
+                  color(66, 100, 133),
+                  color(0, 100, 200))
+        stroke(colors[i])
+        draw_poly(scale_poly(t, siz))
+    
+def draw_poly(p_list):
+    beginShape()
+    for p in p_list:
+       vertex(p[0], p[1], p[0] * p[1] / space)
+    endShape(CLOSE)
+        
+def lerp_poly(p0, p1, t):
+    pt = []
+    for sp0, sp1 in zip(p0, p1):
+        pt.append((lerp(sp0[0], sp1[0], t),
+                   lerp(sp0[1], sp1[1], t)))
+    return pt
+        
+def scale_poly(p_list, s):
+    return [(p[0] * s, p[1] * s) for p in p_list]
+
+def keyPressed():
+    if key == "s":
+        saveFrame(SKETCH_NAME + OUTPUT)
+        
+        
+def settings():
+    """ print markdown to add at the sketch-a-day page"""
+    from os import path
+    global SKETCH_NAME, OUTPUT
+    SKETCH_NAME = path.basename(sketchPath())
+    OUTPUT = ".png"
+    println(
+        """
+![{0}]({2}/{0}/{0}{1})
+
+[{0}](https://github.com/villares/sketch-a-day/tree/master/{2}/{0}) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+""".format(SKETCH_NAME, OUTPUT, year())
+    )