add Object & Block

block.go

@@ -0,0 +1,20 @@
+package molecular
+
+type Facing uint8
+
+//go:generate stringer -type=Facing
+const (
+	TOP Facing = iota
+	BOTTOM
+	LEFT
+	RIGHT
+	FRONT
+	BACK
+)
+
+type Block interface {
+	Mass() float64
+	Material(f Facing) *Material
+	Outline() *Cube
+	Tick(dt float64)
+}

engine.go

@@ -1,7 +1,9 @@
 package molecular
 
 type Config struct {
+	// MinSpeed means the minimum positive speed
 	MinSpeed float64
+	// MaxSpeed means the maximum positive speed
 	MaxSpeed float64
 }
 
@@ -18,3 +20,7 @@ func NewEngine(cfg Config) *Engine {
 func (e *Engine) Config() Config {
 	return e.cfg
 }
+
+func (e *Engine) Tick(dt float64) {
+	// TODO
+}

motion.go

@@ -8,8 +8,24 @@ const (
 	C = 299792458.0 // The speed of light
 )
 
-// RelativeDeltaTime returns the actuall time that relative to the obeserver (server),
-// with given speed and the time relative to the moving object
-func RelativeDeltaTime(t float64, speed float64) float64 {
-	return t / math.Sqrt(1-speed*speed/C*C)
+// RelativeDeltaTime returns the actual delta time that relative to the moving object,
+// with given speed and the delta time relative to the observer (or the server)
+func (e *Engine) RelativeDeltaTime(t float64, speed float64) float64 {
+	if t == 0 {
+		return 0
+	}
+	if t < 0 {
+		panic("molecular.Engine: delta time cannot be negative")
+	}
+	if speed < 0 {
+		panic("molecular.Engine: speed cannot be negative")
+	}
+	if speed >= C {
+		return math.SmallestNonzeroFloat64
+	}
+	t2 := t * math.Sqrt(1-speed*speed/(C*C))
+	if t2 == 0 {
+		return math.SmallestNonzeroFloat64
+	}
+	return t2
 }

object.go

@@ -0,0 +1,25 @@
+package molecular
+
+type AnchorObject struct {
+	rpos map[*AnchorObject]Vec // the pos relative to other known anchors
+	objs map[*Object]struct{}
+}
+
+func (a *AnchorObject) Tick(dt float64) {
+	for o, _ := range a.objs {
+		o.Tick(dt)
+	}
+}
+
+type Object struct {
+	anchor *AnchorObject
+	pos    Vec // the position relative to the anchor
+	facing Vec
+	blocks []Block
+}
+
+func (o *Object) Tick(dt float64) {
+	for _, b := range o.blocks {
+		b.Tick(dt)
+	}
+}

package.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-// molecule is a 3D physics engine that designed for realistic gravity
+// molecule is a 3D physics engine that designed for realistic star system
 //
 // The default units used by this package:
 // Distance and Position: m (meter)