world view ray casting

internal/world/viewray.go

@@ -0,0 +1,48 @@
+package world
+
+import "edgaru089.ml/go/gl01/internal/util/itype"
+
+// CastViewRay
+func (w *World) CastViewRay(from, dir itype.Vec3d, maxlen float64) (ok bool, blockcoord itype.Vec3i, face itype.Direction, where itype.Vec3d, dist float64) {
+
+	bfrom := from.Floor()
+	bfromdir := itype.Direction(-1)
+	for bfrom.ToFloat64().Addv(0.5, 0.5, 0.5).Add(from.Negative()).Length() < maxlen {
+		for todir := itype.Direction(0); todir < 6; todir++ {
+			if todir == bfromdir {
+				continue
+			}
+
+			bto := bfrom.Add(itype.DirectionVeci[todir])
+			block := w.Block(bto)
+
+			if block.Id != 0 {
+				outbox := itype.Boxd{
+					OffX:  float64(bto[0]),
+					OffY:  float64(bto[1]),
+					OffZ:  float64(bto[2]),
+					SizeX: 1,
+					SizeY: 1,
+					SizeZ: 1,
+				}
+				var outface itype.Direction
+				if ok, outface, _, _ = outbox.IntersectRay(from, dir, maxlen); ok {
+					app := block.Appearance(bto)
+					for _, lb := range app.Lookbox {
+						if ok, face, where, dist = lb.IntersectRay(from, dir, maxlen); ok {
+							blockcoord = bto
+							return
+						}
+					}
+				}
+
+				bfromdir = outface.Opposite()
+				bfrom = bto
+				break
+			}
+		}
+	}
+
+	ok = false
+	return
+}