From 92bbaaf38e0d391a74ecd17271e476b23c967358 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 7 Oct 2010 19:31:41 +0000
Subject: [PATCH] Toss out the locality optimizer as it's largely irrelevant to
 graphics hardware Add an LRU cache optimizer instead

---
 mesh_export.py | 310 +++++++++++++++++++++++++++----------------------
 1 file changed, 169 insertions(+), 141 deletions(-)

diff --git a/mesh_export.py b/mesh_export.py
index 1ed2dcde..de11602c 100644
--- a/mesh_export.py
+++ b/mesh_export.py
@@ -101,15 +101,12 @@ class Face:
 	
 	__repr__ = __str__
 
-	def pivot_vertices(self, reverse, *vt):
-		verts = self.verts[:]
-		if reverse:
-			verts.reverse()
-		flags = [(v in vt) for v in verts]
-		l = len(verts)
+	def pivot_vertices(self, *vt):
+		flags = [(v in vt) for v in self.verts]
+		l = len(self.verts)
 		for i in range(l):
 			if flags[i] and not flags[(i+l-1)%l]:
-				return verts[i:]+verts[:i]
+				return self.verts[i:]+self.verts[:i]
 
 	def get_edge(self, v1, v2):	
 		key = make_edge_key(v1.index, v2.index)
@@ -292,7 +289,7 @@ class Mesh:
 			v.tan.normalize()
 			v.bino.normalize()
 
-	def create_strip(self, face, reverse, debug):
+	def create_strip(self, face, max_len, debug):
 		edge = None
 		for e in face.edges:
 			other = e.other_face(face)
@@ -304,20 +301,21 @@ class Mesh:
 			return None
 
 		if debug:
-			print "Starting strip from %s, edge %s, reverse=%s"%([v.index for v in face.verts], (edge.v1.index, edge.v2.index), reverse)
+			print "Starting strip from %s, edge %s"%([v.index for v in face.verts], (edge.v1.index, edge.v2.index))
 
-		verts = face.pivot_vertices(reverse, edge.v1, edge.v2)
+		verts = face.pivot_vertices(edge.v1, edge.v2)
 		if len(verts)==3:
 			result = [verts[-1], verts[0]]
 		else:
 			result = [verts[-2], verts[-1]]
 
 		while 1:
-			verts = face.pivot_vertices(reverse, *result[-2:])
-			k = len(result)%2
 			if debug:
 				print "  Adding %s"%face
 
+			verts = face.pivot_vertices(*result[-2:])
+			k = len(result)%2
+
 			face.flag = True
 			if len(verts)==4 and not k:
 				result.append(verts[3])
@@ -325,6 +323,11 @@ class Mesh:
 			if len(verts)==4 and k:
 				result.append(verts[3])
 
+			if len(result)>=max_len:
+				if debug:
+					print "  Max length exceeded"
+				break
+
 			edge = face.get_edge(*result[-2:])
 
 			if debug:
@@ -341,6 +344,37 @@ class Mesh:
 		return result
 
 
+class VertexCache:
+	def __init__(self, size):
+		self.size = size
+		self.slots = [-1]*self.size
+
+	def fetch(self, v):
+		hit = v.index in self.slots
+		if hit:
+			self.slots.remove(v.index)
+		self.slots.append(v.index)
+		if not hit:
+			del self.slots[0]
+		return hit
+
+	def fetch_strip(self, strip):
+		hits = 0
+		for v in strip:
+			if self.fetch(v):
+				hits += 1
+		return hits
+
+	def test_strip(self, strip):
+		hits = 0
+		for i in range(len(strip)):
+			if i>=self.size:
+				break
+			if strip[i].index in self.slots[i:]:
+				hits += 1
+		return hits
+
+
 class Exporter:
 	def __init__(self, fn):
 		self.filename = fn
@@ -350,33 +384,117 @@ class Exporter:
 			self.out_file = file(fn, "w")
 		self.use_strips = True
 		self.use_degen_tris = True
-		self.optimize_locality = True
+		self.max_strip_len = 1024
+		self.optimize_cache = False
+		self.cache_size = 64
 		self.export_lines = True
 		self.tbn_vecs = False
 		self.debug = False
 		self.strip_debug = False
 		self.split_debug = False
 
-	def get_locality(self, strip):
-		total = 0
-		for i in range(1, len(strip)):
-			if strip[i].index!=strip[i-1].index:
-				total += 1.0/(abs(strip[i].index-strip[i-1].index))
-		return total/len(strip)
-
-	def get_followers(self, strip):
-		result = {}
-		for i in range(len(strip)-1):
-			v = strip[i]
-			n = strip[i+1]
-			if v.index!=n.index:
-				if v.index not in result:
-					result[v.index] = {}
-				if n.index not in result[v.index]:
-					result[v.index][n.index] = 1
+	def stripify(self, mesh):
+		for f in mesh.faces:
+			f.flag = False
+
+		strips = []
+
+		while 1:
+			best = 5
+			face = None
+			for f in mesh.faces:
+				if f.flag:
+					continue
+				score = 0
+				for e in f.edges:
+					other = e.other_face(f)
+					if other and not other.flag:
+						score += 1
+				if score>0 and score<best:
+					face = f
+					best = score
+
+			if not face:
+				break
+
+			strip = mesh.create_strip(face, self.max_strip_len, self.strip_debug)
+			if strip:
+				strips.append(strip)
+
+		loose = [f for f in mesh.faces if not f.flag]
+
+		if self.debug:
+			print "%d strips:"%len(strips)
+			for i in range(len(strips)):
+				print "  %d: %d indices"%(i, len(strips[i]))
+			print "%d loose faces"%len([f for f in mesh.faces if not f.flag])
+			nind = sum([len(s) for s in strips])+sum([len(f.verts) for f in loose])
+			print "%d indices total"%nind
+
+		if self.use_degen_tris and strips:
+			big_strip = []
+
+			cache = None
+			total_hits = 0
+			if self.optimize_cache:
+				cache = VertexCache(self.cache_size)
+
+			while strips:
+				best = 0
+				if cache:
+					best_hits = 0
+					for i in range(len(strips)):
+						hits = cache.test_strip(strips[i])
+						if hits>best_hits:
+							best = i
+							best_hits = hits
+
+				s = strips[best]
+
+				if big_strip:
+					glue = [big_strip[-1], s[0]]
+					if len(big_strip)%2:
+						glue += [s[0]]
+
+					big_strip += glue
+					if cache:
+						total_hits += cache.fetch_strip(glue)
+
+				big_strip += s
+				if cache:
+					total_hits += cache.fetch_strip(s)
+
+				del strips[best]
+
+			for f in loose:
+				if len(big_strip)%2:
+					order = (-1, -2, 0, 1)
 				else:
-					result[v.index][n.index] += 1
-		return result
+					order = (0, 1, -1, -2)
+				verts = [f.verts[i] for i in order[:len(f.verts)]]
+				if big_strip:
+					glue = [big_strip[-1], verts[0]]
+					big_strip += glue
+					if cache:
+						total_hits += cache.fetch_strip(glue)
+				big_strip += verts
+				if cache:
+					total_hits += cache.fetch_strip(verts)
+
+			strips = [big_strip]
+			loose = []
+			
+			if self.debug:
+				nind = len(big_strip)
+				print "Big strip has %d indices"%nind
+				if self.optimize_cache:
+					print "%d cache hits"%total_hits
+
+		if self.debug:
+			ntris = sum([len(f.verts)-2 for f in mesh.faces])
+			print "%.2f indices per triangle"%(float(nind)/max(ntris, 1))
+
+		return strips, loose
 
 	def export(self):
 		scene = bpy.data.scenes.active
@@ -411,104 +529,7 @@ class Exporter:
 
 		strips = []
 		if self.use_strips:
-			for f in mesh.faces:
-				f.flag = False
-
-			while 1:
-				best = 5
-				face = None
-				for f in mesh.faces:
-					if f.flag:
-						continue
-					score = 0
-					for e in f.edges:
-						other = e.other_face(f)
-						if other and not other.flag:
-							score += 1
-					if score>0 and score<best:
-						face = f
-						best = score
-
-				if not face:
-					break
-
-				strip = mesh.create_strip(face, self.use_degen_tris and sum([len(s) for s in strips])%2, self.strip_debug)
-				if strip:
-					strips.append(strip)
-
-			if self.debug:
-				print "%d strips:"%len(strips)
-				for i in range(len(strips)):
-					print "  %d: %d indices"%(i, len(strips[i]))
-				print "%d loose faces"%len([f for f in mesh.faces if not f.flag])
-				nind = sum([len(s) for s in strips])+sum([len(f.verts) for f in mesh.faces if not f.flag])
-				print "%d indices total"%nind
-
-			if self.use_degen_tris and strips:
-				big_strip = []
-				for s in strips:
-					if big_strip:
-						big_strip += [big_strip[-1], s[0]]
-					big_strip += s
-
-				for f in mesh.faces:
-					if not f.flag:
-						if len(big_strip)%2:
-							order = (-1, -2, 0, 1)
-						else:
-							order = (0, 1, -1, -2)
-						if big_strip:
-							big_strip += [big_strip[-1], f.verts[order[0]]]
-						big_strip += [f.verts[i] for i in order[:len(f.verts)]]
-						f.flag = True
-
-				strips = [big_strip]
-				
-				if self.debug:
-					nind = len(big_strip)
-					print "Big strip has %d indices"%len(big_strip)
-
-		if self.debug:
-			print "%.2f indices per triangle"%(float(nind)/max(ntris, 1))
-			print "Locality before optimization: "+" ".join(["%.3f"%self.get_locality(s) for s in strips])
-
-		if self.optimize_locality and self.use_strips and strips:
-			followers = {}
-			for s in strips:
-				followers.update(self.get_followers(s))
-
-			verts2 = []
-			vert = strips[0][0]
-			while 1:
-				vert.flag = True
-				verts2.append(vert)
-
-				next = None
-				if vert.index in followers:
-					flw = followers[vert.index]
-					best = 0
-					for n in flw:
-						if flw[n]>best and not mesh.verts[n].flag:
-							next = mesh.verts[n]
-							best = flw[n]+0.9/abs(vert.index-n)
-
-				if not next:
-					for v in mesh.verts:
-						if not v.flag:
-							next = v
-							break
-					if not next:
-						break
-
-				vert = next
-
-			mesh.verts = verts2
-
-			for i in range(len(mesh.verts)):
-				mesh.verts[i].index = i
-
-			if self.debug:
-				print "Locality after optimization: "+" ".join(["%.3f"%self.get_locality(s) for s in strips])
+			strips, loose = self.stripify(mesh)
 
 		self.out_file.write("vertices NORMAL3")
 		if mesh.faceUV:
@@ -546,13 +567,12 @@ class Exporter:
 			self.out_file.write(";\n};\n")
 
 		first = True
-		for f in mesh.faces:
-			if not f.flag:
-				if first:
-					self.out_file.write("batch TRIANGLES\n{\n")
-					first = False
-				for i in range(2, len(f.verts)):
-					self.out_file.write("\tindices %u %u %u;\n"%(f.verts[0].index, f.verts[i-1].index, f.verts[i].index))
+		for f in loose:
+			if first:
+				self.out_file.write("batch TRIANGLES\n{\n")
+				first = False
+			for i in range(2, len(f.verts)):
+				self.out_file.write("\tindices %u %u %u;\n"%(f.verts[0].index, f.verts[i-1].index, f.verts[i].index))
 		if not first:
 			self.out_file.write("};\n")
 
@@ -571,7 +591,9 @@ class FrontEnd:
 	def run(self):
 		self.use_strips = Blender.Draw.Create(self.config.get('use_strips', True))
 		self.use_degen_tris = Blender.Draw.Create(self.config.get('use_degen_tris', True))
-		self.optimize_locality = Blender.Draw.Create(self.config.get('optimize_locality', True))
+		self.max_strip_len = Blender.Draw.Create(self.config.get('max_strip_len', 1024))
+		self.optimize_cache = Blender.Draw.Create(self.config.get('optimize_cache', False))
+		self.cache_size = Blender.Draw.Create(self.config.get('cache_size', 64))
 		self.export_lines = Blender.Draw.Create(self.config.get('export_lines', False))
 		self.tbn_vecs = Blender.Draw.Create(self.config.get('tbn_vecs', False))
 		self.debug = Blender.Draw.Create(self.config.get('debug', False))
@@ -580,7 +602,9 @@ class FrontEnd:
 		ret = Blender.Draw.PupBlock("Export MSP GL mesh",
 			[("Use strips", self.use_strips, "Generage OpenGL triangle strips"),
 				("Use degen tris", self.use_degen_tris, "Use degenerate triangles to combine triangle strips"),
-				("Optimize locality", self.optimize_locality),
+				("Max strip len", self.max_strip_len, 4, 16384, "Maximum length of a triangle strip"),
+				("Optimize cache", self.optimize_cache, "Optimize for vertex cache"),
+				("Cache size", self.cache_size, 8, 1024, "Cache size to optimize for"),
 				("Export lines", self.export_lines, "Export lone edges as lines"),
 				("Compute T/B vecs", self.tbn_vecs, "Compute tangent/binormal vectors for bumpmapping"),
 				("Debugging options"),
@@ -598,7 +622,9 @@ class FrontEnd:
 	def export(self, fn):
 		self.config['use_strips'] = self.use_strips.val
 		self.config['use_degen_tris'] = self.use_degen_tris.val
-		self.config['optimize_locality'] = self.optimize_locality.val
+		self.config['max_strip_len'] = self.max_strip_len.val
+		self.config['optimize_cache'] = self.optimize_cache.val
+		self.config['cache_size'] = self.cache_size.val
 		self.config['export_lines'] = self.export_lines.val
 		self.config['tbn_vecs'] = self.tbn_vecs.val
 		self.config['debug'] = self.debug.val
@@ -613,7 +639,9 @@ class FrontEnd:
 		exp = Exporter(fn)
 		exp.use_strips = self.use_strips.val
 		exp.use_degen_tris = self.use_degen_tris.val
-		exp.optimize_locality = self.optimize_locality.val
+		exp.max_strip_len = self.max_strip_len.val
+		exp.optimize_cache = self.optimize_cache.val
+		exp.cache_size = self.cache_size.val
 		exp.export_lines = self.export_lines.val
 		exp.tbn_vecs = self.tbn_vecs.val
 		exp.debug = self.debug.val
-- 
2.43.0