opacity factor for particle system

src/game-lib-d3-api-particle.js

@@ -5,6 +5,8 @@
  * @param lifeTime
  * @param elapsed
  * @param mesh
+ * @param opacityType
+ * @param opacityFactor
  * @param positionOffsetType
  * @param positionOffset
  * @param positionOffsetFn
@@ -28,6 +30,8 @@ GameLib.D3.API.Particle = function(
     lifeTime,
     elapsed,
     mesh,
+    opacityType,
+    opacityFactor,
     positionOffsetType,
     positionOffset,
     positionOffsetFn,
@@ -70,6 +74,16 @@ GameLib.D3.API.Particle = function(
     }
     this.mesh = mesh;
 
+    if (GameLib.Utils.UndefinedOrNull(opacityType)) {
+        opacityType = GameLib.D3.Particle.OPACITY_TYPE_CONSTANT;
+    }
+    this.opacityType = opacityType;
+
+    if (GameLib.Utils.UndefinedOrNull(opacityFactor)) {
+        opacityFactor = 0.01;
+    }
+    this.opacityFactor = opacityFactor;
+
     if (GameLib.Utils.UndefinedOrNull(positionOffsetType)) {
         positionOffsetType = GameLib.D3.Particle.POSITION_OFFSET_TYPE_CONSTANT;
     }
@@ -171,6 +185,8 @@ GameLib.D3.API.Particle.FromObject = function(objectParticle) {
         objectParticle.lifeTime,
         objectParticle.elapsed,
         apiMesh,
+        objectParticle.opacityType,
+        objectParticle.opacityFactor,
         objectParticle.positionOffsetType,
         GameLib.API.Vector3.FromObject(objectParticle.positionOffset),
         objectParticle.positionOffsetFn,

src/game-lib-d3-particle.js

@@ -27,6 +27,8 @@ GameLib.D3.Particle = function(
         apiParticle.lifeTime,
         apiParticle.elapsed,
         apiParticle.mesh,
+        apiParticle.opacityType,
+        apiParticle.opacityFactor,
         apiParticle.positionOffsetType,
         apiParticle.positionOffset,
         apiParticle.positionOffsetFn,
@@ -109,6 +111,10 @@ GameLib.D3.Particle = function(
 GameLib.D3.Particle.prototype = Object.create(GameLib.D3.API.Particle.prototype);
 GameLib.D3.Particle.prototype.constructor = GameLib.D3.Particle;
 
+GameLib.D3.Particle.OPACITY_TYPE_CONSTANT             = 0x1;
+GameLib.D3.Particle.OPACITY_TYPE_DECREASE_LINEAR      = 0x2;
+GameLib.D3.Particle.OPACITY_TYPE_INCREASE_LINEAR      = 0x3;
+
 GameLib.D3.Particle.POSITION_OFFSET_TYPE_CONSTANT     = 0x1;
 GameLib.D3.Particle.POSITION_OFFSET_TYPE_RANDOM       = 0x2;
 GameLib.D3.Particle.POSITION_OFFSET_TYPE_FUNCTION     = 0x3;
@@ -186,6 +192,8 @@ GameLib.D3.Particle.prototype.toApiObject = function() {
         this.lifeTime,
         this.elapsed,
         GameLib.Utils.IdOrNull(this.mesh),
+        this.opacityType,
+        this.opacityFactor,
         this.positionOffsetType,
         this.positionOffset.toApiObject(),
         this.positionOffsetFn,

src/game-lib-system-gui.js

@@ -714,7 +714,19 @@ GameLib.System.GUI.prototype.buildControl = function(folder, componentTemplate,
 					}
 				)
 			);
-		} else if (property === 'positionOffsetType') {
+		} else if (property === 'opacityType') {
+            controllers.push(
+                folder.add(
+                    object,
+                    property,
+                    {
+                        'constant': GameLib.D3.Particle.OPACITY_TYPE_CONSTANT,
+                        'decrease': GameLib.D3.Particle.OPACITY_TYPE_DECREASE_LINEAR,
+                        'increase': GameLib.D3.Particle.OPACITY_TYPE_INCREASE_LINEAR
+                    }
+                )
+            );
+        } else if (property === 'positionOffsetType') {
             controllers.push(
                 folder.add(
                     object,
@@ -1133,6 +1145,7 @@ GameLib.System.GUI.prototype.buildControl = function(folder, componentTemplate,
 			 */
 			if (
 				property === 'opacity' ||
+				property === 'opacityFactor' ||
 				property === 'metalness' ||
 				property === 'roughness'
 			) {

src/game-lib-system-particle.js

@@ -132,7 +132,13 @@ GameLib.System.Particle.prototype.beforeRender = function(data) {
 
                     particle.quaternion.copy(particleEngine.camera.instance.quaternion);
 
-                    particle.material.opacity -= 0.033333;
+                    if (particleEngine.templateParticle.opacityType === GameLib.D3.Particle.OPACITY_TYPE_INCREASE_LINEAR) {
+                        particle.material.opacity += particleEngine.templateParticle.opacityFactor;
+                    }
+
+                    if (particleEngine.templateParticle.opacityType === GameLib.D3.Particle.OPACITY_TYPE_DECREASE_LINEAR) {
+                        particle.material.opacity -= particleEngine.templateParticle.opacityFactor;
+                    }
 
                     particle.userData.elapsed += data.delta;
                     if (