// Evaluates the rules in the given XML stream and returns a list of curves
func Evaluate(stream io.Reader) Curve {
var curve Curve
var lsys LSystem
bytes, _ := ioutil.ReadAll(stream)
if err := xml.Unmarshal(bytes, &lsys); err != nil {
fmt.Println("Error parsing XML file:", err)
return curve
}
// Parse the transform strings
lsys.Matrices = make(MatrixCache)
for _, rule := range lsys.Rules {
for _, call := range rule.Calls {
lsys.Matrices.ParseString(call.Transforms)
}
for _, inst := range rule.Instances {
lsys.Matrices.ParseString(inst.Transforms)
}
}
lsys.Matrices[""] = *vmath.M4Identity()
// Provide defaults
for i := range lsys.Rules {
r := &lsys.Rules[i]
if r.Weight == 0 {
r.Weight = 1
}
}
// Seed the random-number generator and pick the entry rule
random := rand.New(rand.NewSource(42))
start := StackNode{
RuleIndex: lsys.PickRule("entry", random),
Transform: vmath.M4Identity(),
}
lsys.ProcessRule(start, &curve, random)
return curve
}
// Parse a string in the xform language and add the resulting matrix to the lookup table.
// Examples:
// "rx -2 tx 0.1 sa 0.996"
// "s 0.55 2.0 1.25"
func (cache *MatrixCache) ParseString(s string) {
if len(s) == 0 {
return
}
reader := bufio.NewReader(strings.NewReader(s))
xform := vmath.M4Identity()
readFloat := func() float32 {
sx, _ := reader.ReadString(' ')
fx, _ := strconv.ParseFloat(strings.TrimSpace(sx), 32)
return float32(fx)
}
for {
token, err := reader.ReadString(' ')
token = strings.TrimSpace(token)
switch token {
case "s":
x := readFloat()
y := readFloat()
z := readFloat()
m := vmath.M4Scale(x, y, z)
xform = m.Compose(xform)
case "sa":
a := readFloat()
m := vmath.M4Scale(a, a, a)
xform = m.Compose(xform)
case "t":
x := readFloat()
y := readFloat()
z := readFloat()
m := vmath.M4Translate(x, y, z)
xform = m.Compose(xform)
case "tx":
x := readFloat()
m := vmath.M4Translate(x, 0, 0)
xform = m.Compose(xform)
case "ty":
y := readFloat()
m := vmath.M4Translate(0, y, 0)
xform = m.Compose(xform)
case "tz":
z := readFloat()
m := vmath.M4Translate(0, 0, z)
xform = m.Compose(xform)
case "rx":
x := radians(readFloat())
m := vmath.M4RotateX(-x)
xform = m.Compose(xform)
case "ry":
y := radians(readFloat())
m := vmath.M4RotateY(-y)
xform = m.Compose(xform)
case "rz":
z := radians(readFloat())
m := vmath.M4RotateZ(-z)
xform = m.Compose(xform)
case "":
default:
fmt.Println("Unknown token: ", token)
}
if err != nil {
break
}
}
(*cache)[s] = *xform
return
}