add iso.go

engine/iso.go

@@ -0,0 +1,29 @@
+package engine
+
+// Box describes an axis-aligned rectangular prism.
+type Box struct {
+	X, Y, Z int // coordinate of the left-top-farthest corner
+	W, H, D int // width, height, depth
+}
+
+// IsoProjection translates an integer 3D coordinate into an integer 2D
+// coordinate.
+type IsoProjection struct {
+	ZX, ZY int
+}
+
+// Project projects a 3D coordinate into 2D.
+// If ZX = 0, x is unchanged; similarly for ZY and y.
+// Otherwise, x becomes x + z/ZX and y becomes y + z/ZY.
+// This is because there's little reason for an isometric projection in a game
+// to exaggerate the Z position.
+func (π IsoProjection) Project(x, y, z int) (xp, yp int) {
+	xp, yp = x, y
+	if π.ZX != 0 {
+		xp += z / π.ZX
+	}
+	if π.ZY != 0 {
+		yp += z / π.ZY
+	}
+	return xp, yp
+}