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105 lines
2.4 KiB
Python
105 lines
2.4 KiB
Python
# Playground for working through scanline decomposition algorithm
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# 1. Shadow Off
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# 2. Draw Playfield (sprite OR overlay) AND NOT solid_overlay
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# 3. Draw sprites
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sprites = [
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{ 'top': 10, 'bottom': 17 },
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{ 'top': 14, 'bottom': 29 }
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]
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overlays = [
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{ 'top': 0, 'bottom': 7 }
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]
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MAX_HEIGHT = 199
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# Combine a list on ranges into a minimal list by merging overlapping ranges
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def simplify(a):
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b = []
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if len(a) > 0:
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last = a[0]
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start = last['top']
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for r in a[1:]:
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if r['top'] <= last['bottom']:
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last = r
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continue
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b.append([start, last['bottom']])
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last = r
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start = r['top']
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b.append([start, last['bottom']])
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return b
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# Given two sorted lists, merge them together into a minimal set of ranges. This could
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# be done as a list merge nd then a combine step, but we want to be more efficient and
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# do the merge-and-compbine at the same time
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def merge(a, b):
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if len(a) == 0:
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return simplify(b)
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if len(b) == 0:
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return simplify(a)
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c = []
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i = j = 0
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while i < len(a) and j < len(b):
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if a[i]['top'] <= b[j]['top']:
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c.append(a[i])
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i += 1
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else:
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c.append(b[j])
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j += 1
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if i < len(a):
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c.extend(a[i:])
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if j < len(b):
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c.extend(b[j:])
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return simplify(c)
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# Find the lines that need to be drawn with shadowing off
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def get_shadow_off_bg(sprites):
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ranges = []
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if len(sprites) > 0:
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last = sprites[0]
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start = last['top']
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for sprite in sprites[1:]:
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if sprite['top'] <= last['bottom']:
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last = sprite
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continue
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ranges.push([start, last['bottom']])
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start = sprite['top']
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last = sprite
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ranges.append([start, last['bottom']])
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return ranges
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def complement(ranges):
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comp = []
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if len(ranges) > 0:
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if ranges[0][0] > 0:
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comp.append([0, ranges[0][0]])
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for i in range(1, len(ranges)):
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comp.append([ranges[i-1][1]+1, ranges[i][0]])
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last = ranges[len(ranges)-1]
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if last[1] < MAX_HEIGHT:
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comp.append([last[1]+1, MAX_HEIGHT])
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return comp
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else:
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return [0, MAX_HEIGHT]
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r = get_shadow_off_bg(sprites)
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print(r)
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print(complement(r))
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print(merge(sprites, overlays)) |