Sor*_*ona 9 opengl algorithm scala .obj index-buffer
我正在尝试加载.obj文件并在帮助下绘制它glDrawElements.
现在,glDrawArrays一切都运作完美,但它 - 当然 - 效率低下.
我现在遇到的问题是,.obj文件使用多个索引缓冲区(对于每个属性),而OpenGL只能使用一个.所以我需要相应地映射它们.
那里有很多伪算法,我甚至找到了一个C++实现.我确实知道很多C++,但奇怪的是我没有帮助我在Scala中实现.
让我们来看看:
private def parseObj(path: String): Model =
{
val objSource: List[String] = Source.fromFile(path).getLines.toList
val positions: List[Vector3] = objSource.filter(_.startsWith("v ")).map(_.split(" ")).map(v => new Vector3(v(1).toFloat,v(2).toFloat,v(3).toFloat))//, 1.0f))
val normals: List[Vector4] = objSource.filter(_.startsWith("vn ")).map(_.split(" ")).map(v => new Vector4(v(1)toFloat,v(2).toFloat, v(3).toFloat, 0.0f))
val textureCoordinates: List[Vector2] = objSource.filter(_.startsWith("vt ")).map(_.split(" ")).map(v => new Vector2(v(1).toFloat, 1-v(2).toFloat)) // TODO 1-y because of blender
val faces: List[(Int, Int, Int)] = objSource.filter(_.startsWith("f ")).map(_.split(" ")).flatten.filterNot(_ == "f").map(_.split("/")).map(a => ((a(0).toInt, a(1).toInt, a(2).toInt)))
val vertices: List[Vertex] = for(face <- faces) yield(new Vertex(positions(face._1-1), textureCoordinates(face._2-1)))
val f: List[(Vector3, Vector2, Vector4)] = for(face <- faces) yield((positions(face._1-1), textureCoordinates(face._2-1), normals(face._3-1)))
println(f.mkString("\n"))
val indices: List[Int] = faces.map(f => f._1-1) // Wrong!
new Model(vertices.toArray, indices.toArray)
}
这val indices: List[Int]是我的第一个天真的方法,当然是错的.但是让我们从顶部开始:
我加载文件并完成它.(我假设您知道.obj文件是如何组成的)
我读了顶点,纹理坐标和法线.然后我来到了脸上.
现在,我的示例中的每个面都有3个值来v_x, t_y, n_z定义vertexAtIndexX, textureCoordAtIndexY, normalAtIndexZ.因此,每个定义一个顶点,而其中三个(或文件中的一行)定义一个面/多边形/三角形.
在val vertices: List[Vertex] = for(face <- faces) yield(new Vertex(positions(face._1-1), textureCoordinates(face._2-1)))我实际上尝试创建顶点(一个案例类,目前只持有位置和纹理坐标,现在忽略法线)
真正的问题是这一行:
val indices: List[Int] = faces.map(f => f._1-1) // Wrong!
要获得真正的指数基本上,我需要做到这一点,而不是的
val vertices: List[Vertex] = for(face <- faces) yield(new Vertex(positions(face._1-1), textureCoordinates(face._2-1)))
和
val indices: List[Int] = faces.map(f => f._1-1) // Wrong!
伪代码:
Iterate over all faces
Iterate over all vertices in a face
Check if we already have that combination of(position, texturecoordinate, normal) in our newVertices
if(true)
indices.put(indexOfCurrentVertex)
else
create a new Vertex from the face
store the new vertex in the vertex list
indices.put(indexOfNewVertex)
然而,我完全陷入困境.我尝试了不同的东西,但无法想出一个真正有用的漂亮而干净的解决方案.
像:
val f: List[(Vector3, Vector2, Vector4)] = for(face <- faces) yield((positions(face._1-1), textureCoordinates(face._2-1), normals(face._3-1)))
并且试图f.distinct不工作,因为没有什么可以区分,所有条目都是唯一的,如果我查看文件这完全有意义,但这就是伪代码告诉我检查的内容.
当然那么我需要相应地填写指数(最好是单线并具有很多功能美)
但我应该试着找到重复的东西,所以...我有点困惑.我猜我把所有的参考都混合了不同的"顶点"和"位置".
所以,我认为是错误的,还是算法/思考正确,我只需要在漂亮,干净(实际工作)的Scala代码中实现它？
拜托,赐教!
根据评论,我做了一些更新:
var index: Int = 0
val map: mutable.HashMap[(Int, Int, Int), Int] = new mutable.HashMap[(Int, Int, Int), Int].empty
val combinedIndices: ListBuffer[Int] = new ListBuffer[Int]
for(face <- faces)
{
val vID: Int = face._1-1
val nID: Int = face._2-1
val tID: Int = face._3-1
var combinedIndex: Int = -1
if(map.contains((vID, nID, tID)))
{
println("We have a duplicate, wow!")
combinedIndex = map.get((vID, nID, tID)).get
}
else
{
combinedIndex = index
map.put((vID, nID, tID), combinedIndex)
index += 1
}
combinedIndices += combinedIndex
}
面孔仍然是:
val faces: List[(Int, Int, Int)] = objSource.filter(_.startsWith("f ")).map(_.split(" ")).flatten.filterNot(_ == "f").map(_.split("/")).map(a => ((a(0).toInt, a(1).toInt, a(2).toInt)))
有趣的事实我显然仍然不理解它,因为这样我从来没有得到重复!
这意味着combinedIndices最后只是拥有如下自然数:
ListBuffer(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ...)
这是 javascript（抱歉不是 scala），但它有注释并且应该很容易转换。
// bow-tie
var objString = "v 0 0 0\nv 1 1 0\nv 1 -1 0\nv -1 1 0\nv -1 -1 0\n" +
"vt 0 .5\nvt 1 1\nvt 1 0\n" +
"vn 0 0 1\n" +
"f 1/1/1 2/2/1 3/3/1\nf 1/1/1 4/2/1 5/3/1";
// output indices should be [0, 1, 2, 0, 3, 4]
// parse the file
var lines = objString.split("\n");
var data = lines.map(function(line) { return line.split(" "); });
var v = [];
var t = [];
var n = [];
var f = [];
var indexMap = new Map(); // HashMap<face:string, index:integer>
var nextIndex = 0;
var vertices = [];
var indices = [];
// fill vertex, texture and normal arrays
data.filter(function(d) { return d[0] == "v"; }).forEach(function(d) { v.push([parseFloat(d[1]), parseFloat(d[2]), parseFloat(d[3])]); });
data.filter(function(d) { return d[0] == "vt"; }).forEach(function(d) { t.push([parseFloat(d[1]), parseFloat(d[2])]); });
data.filter(function(d) { return d[0] == "vn"; }).forEach(function(d) { n.push([parseFloat(d[1]), parseFloat(d[2]), parseFloat(d[3])]); });
//
console.log("V", v.toString());
console.log("T", t.toString());
console.log("N", n.toString());
// create vertices and indices arrays by parsing faces
data.filter(function(d) { return d[0] == "f"; }).forEach(function(d) {
var f1 = d[1].split("/").map(function(d) { return parseInt(d)-1; });
var f2 = d[2].split("/").map(function(d) { return parseInt(d)-1; });
var f3 = d[3].split("/").map(function(d) { return parseInt(d)-1; });
// 1
if(indexMap.has(d[1].toString())) {
indices.push(indexMap.get(d[1].toString()));
} else {
vertices = vertices.concat(v[f1[0]]).concat(t[f1[1]]).concat(n[f1[2]]);
indexMap.set(d[1].toString(), nextIndex);
indices.push(nextIndex++);
}
// 2
if(indexMap.has(d[2].toString())) {
indices.push(indexMap.get(d[2].toString()));
} else {
vertices = vertices.concat(v[f2[0]]).concat(t[f2[1]]).concat(n[f2[2]]);
indexMap.set(d[2].toString(), nextIndex);
indices.push(nextIndex++);
}
// 3
if(indexMap.has(d[3].toString())) {
indices.push(indexMap.get(d[3].toString()));
} else {
vertices = vertices.concat(v[f3[0]]).concat(t[f3[1]]).concat(n[f3[2]]);
indexMap.set(d[3].toString(), nextIndex);
indices.push(nextIndex++);
}
});
//
console.log("Vertices", vertices.toString());
console.log("Indices", indices.toString());
输出
V 0,0,0,1,1,0,1,-1,0,-1,1,0,-1,-1,0
T 0,0.5,1,1,1,0
N 0,0,1
Vertices 0,0,0,0,0.5,0,0,1,1,1,0,1,1,0,0,1,1,-1,0,1,0,0,0,1,-1,1,0,1,1,0,0,1,-1,-1,0,1,0,0,0,1
Indices 0,1,2,0,3,4
JSFiddle http://jsfiddle.net/8q7jLvsq/2
我唯一做的不同的事情是使用代表脸部一部分的字符串帽子作为我的索引映射的键（例如：“25/32/5”）。
编辑JSFiddle http://jsfiddle.net/8q7jLvsq/2/ 此版本结合了顶点、纹理和法线的重复值。这会优化重复相同值的 OBJ 文件，使每个面都独一无二。
// bow-tie
var objString = "v 0 0 0\nv 1 1 0\nv 1 -1 0\nv 0 0 0\nv -1 1 0\nv -1 -1 0\n" +
"vt 0 .5\nvt 1 1\nvt 1 0\nvt 0 .5\nvt 1 1\nvt 1 0\n" +
"vn 0 0 1\nvn 0 0 1\nvn 0 0 1\nvn 0 0 1\nvn 0 0 1\nvn 0 0 1\n" +
"f 1/1/1 2/2/2 3/3/3\nf 4/4/4 5/5/5 6/6/6";
// output indices should be [0, 1, 2, 0, 3, 4]
// parse the file
var lines = objString.split("\n");
var data = lines.map(function(line) { return line.split(" "); });
var v = [];
var t = [];
var n = [];
var f = [];
var vIndexMap = new Map(); // map to earliest index in the list
var vtIndexMap = new Map();
var vnIndexMap = new Map();
var indexMap = new Map(); // HashMap<face:string, index:integer>
var nextIndex = 0;
var vertices = [];
var indices = [];
// fill vertex, texture and normal arrays
data.filter(function(d) { return d[0] == "v"; }).forEach(function(d, i) {
v[i] = [parseFloat(d[1]), parseFloat(d[2]), parseFloat(d[3])];
var key = [d[1], d[2], d[3]].toString();
if(!vIndexMap.has(key)) {
vIndexMap.set(key, i);
}
});
data.filter(function(d) { return d[0] == "vt"; }).forEach(function(d, i) {
t[i] = [parseFloat(d[1]), parseFloat(d[2])];
var key = [d[1], d[2]].toString();
if(!vtIndexMap.has(key)) {
vtIndexMap.set(key, i);
}
});
data.filter(function(d) { return d[0] == "vn"; }).forEach(function(d, i) {
n[i] = [parseFloat(d[1]), parseFloat(d[2]), parseFloat(d[3])];
var key = [d[1], d[2], d[3]].toString();
if(!vnIndexMap.has(key)) {
vnIndexMap.set(key, i);
}
});
//
console.log("V", v.toString());
console.log("T", t.toString());
console.log("N", n.toString());
// create vertices and indices arrays by parsing faces
data.filter(function(d) { return d[0] == "f"; }).forEach(function(d) {
var f1 = d[1].split("/").map(function(d, i) {
var index = parseInt(d)-1;
if(i == 0) index = vIndexMap.get(v[index].toString());
else if(i == 1) index = vtIndexMap.get(t[index].toString());
else if(i == 2) index = vnIndexMap.get(n[index].toString());
return index;
});
var f2 = d[2].split("/").map(function(d, i) {
var index = parseInt(d)-1;
if(i == 0) index = vIndexMap.get(v[index].toString());
else if(i == 1) index = vtIndexMap.get(t[index].toString());
else if(i == 2) index = vnIndexMap.get(n[index].toString());
return index;
});
var f3 = d[3].split("/").map(function(d, i) {
var index = parseInt(d)-1;
if(i == 0) index = vIndexMap.get(v[index].toString());
else if(i == 1) index = vtIndexMap.get(t[index].toString());
else if(i == 2) index = vnIndexMap.get(n[index].toString());
return index;
});
// 1
if(indexMap.has(f1.toString())) {
indices.push(indexMap.get(f1.toString()));
} else {
vertices = vertices.concat(v[f1[0]]).concat(t[f1[1]]).concat(n[f1[2]]);
indexMap.set(f1.toString(), nextIndex);
indices.push(nextIndex++);
}
// 2
if(indexMap.has(f2.toString())) {
indices.push(indexMap.get(f2.toString()));
} else {
vertices = vertices.concat(v[f2[0]]).concat(t[f2[1]]).concat(n[f2[2]]);
indexMap.set(f2.toString(), nextIndex);
indices.push(nextIndex++);
}
// 3
if(indexMap.has(f3.toString())) {
indices.push(indexMap.get(f3.toString()));
} else {
vertices = vertices.concat(v[f3[0]]).concat(t[f3[1]]).concat(n[f3[2]]);
indexMap.set(f3.toString(), nextIndex);
indices.push(nextIndex++);
}
});
//
console.log("Vertices", vertices.toString());
console.log("Indices", indices.toString());