new scene system is kind of working. I haven't tested changing between scenes and Transition effect yet, though.

models/device.go

@@ -2,6 +2,7 @@ package models
 
 import (
 	"context"
+	"math"
 	"strings"
 	"time"
 )
@@ -189,6 +190,25 @@ func (d *Device) SetState(newState NewDeviceState) error {
 	return nil
 }
 
+func (s *NewDeviceState) RelativeTo(device Device) NewDeviceState {
+	n := NewDeviceState{}
+
+	if s.Intensity != nil {
+		intensity := device.State.Intensity * *s.Intensity
+		n.Intensity = &intensity
+	}
+	if s.Color != nil {
+		c, err := ParseColorValue(*s.Color)
+		if err == nil {
+			c.Hue = math.Mod(device.State.Color.Hue + c.Hue, 360)
+			c.Saturation *= device.State.Color.Saturation
+			c.Kelvin += device.State.Color.Kelvin
+		}
+	}
+
+	return n
+}
+
 func (s *NewDeviceState) Interpolate(other NewDeviceState, fac float64) NewDeviceState {
 	n := NewDeviceState{}
 

models/scene.go

@@ -69,6 +69,7 @@ type SceneRole struct {
 	TargetKind  ReferenceKind    `json:"targetKind"`
 	TargetValue string           `json:"targetValue"`
 	Interpolate bool             `json:"interpolate"`
+	Relative    bool             `json:"relative"`
 	Order       string           `json:"order"`
 	States      []NewDeviceState `json:"states"`
 }
@@ -81,7 +82,7 @@ type SceneRunContext struct {
 }
 
 func (d *SceneRunContext) PositionFacShifted() float64 {
-	shiftFac := float64((int64(d.Index)+d.IntervalNumber)%int64(d.Length)) * (1 / float64(d.Length))
+	shiftFac := float64(d.IntervalNumber%int64(d.Length)) / float64(d.Length)
 
 	return math.Mod(d.PositionFac()+shiftFac, 1)
 }
@@ -179,6 +180,10 @@ func (r *SceneRole) ApplyEffect(device *Device, c SceneRunContext) (newState New
 		newState = r.State(c.IntervalFac())
 	}
 
+	if r.Relative {
+		newState = newState.RelativeTo(*device)
+	}
+
 	switch r.PowerMode {
 	case SPDevice:
 		newState.Power = nil
@@ -196,6 +201,8 @@ func (r *SceneRole) State(fac float64) NewDeviceState {
 		return r.States[0]
 	}
 
+
+
 	if r.Interpolate {
 		if len(r.States) == 2 {
 			return r.States[0].Interpolate(r.States[1], fac)
@@ -219,8 +226,8 @@ func (r *SceneRole) State(fac float64) NewDeviceState {
 type ScenePowerMode string
 
 const (
-	SPDevice   ScenePowerMode = "Device"   // Device state decides power. Scene state may only power off.
-	SPScene    ScenePowerMode = "Scene"    // Scene state decide power.
+	SPDevice ScenePowerMode = "Device" // Device state decides power. Scene state may only power off.
+	SPScene  ScenePowerMode = "Scene"  // Scene state decide power.
 )
 
 // DeviceSceneAssignment is an entry on the device stack. StartTime and DurationMS are only respected when the scene