In this article, I introduce how to make a shape effect defined by a 3d mesh in Unity’s Particle System.
This time, we create the effect of heart-shaped firework shown above.
Sample
You can experience the sample space in STYLY GALLERY.
You can download the Unity project used in this article from: Fireworks_Sample
Model a heart shape
As we need a mesh to spawn particles from, I modelled it in Maya. 
Since I just needed the outline of a heart shape, I created the outer shape only. Export it as a fbx file and import it to Unity.
Assign heart-shaped mesh to ‘Shape’
Set ‘Rate over Time’ to 0. In the Bursts section, set Time and Count to 0 and 100 respectively. It spawns 100 particles once at 0:00. Set Shape to ‘Mesh’, and Type to ‘Vertex’. In the ‘mesh’ box, select the heart-shaped mesh imported. In the current state, it doesn’t look like firework very well. So I try to add motions a bit. 
Add a spreading-out motion by ‘Spherize Direction’. Set Dampen to 0.3. Colour the heart-shaped particles. 
As it’s a heart, I coloured them pink for now. Adjust the transparency too. 
Adjust the ‘Alpha’ slider so that the particles turn transparent gradually before vanishing. Create the particle when it’s ascending. 
The parameters are set as follows: Rate over Time 0 Bursts/Time 0 Burst/Count 1 Shape ‘Cone’ Angle 0.6 Radius 0.01
Create a curve
Let’s add more motions. Make the particle growing and shrinking when ascending. 
Adjust the curve under ‘Size over Lifetime’. On the curve, double-click the points where you want to change and adjust them so that the particle’s size keeps changing over time.
Link particles’ motions by Sub Emitters
Select ‘Death’ and specify the heart-shaped particles created earlier. It makes the heart-shaped firework spread out when the ascending particle has reached the sky. Make the ascending particle trail a smoke-look particle. 
Set the parameters as follows: Start Lifetime 0.2~0.3 Start Speed 2~3 Start Size 0.3~0.8 Rate over Time 300 
It ended up with the shape shown above. 
Now we completed heart-shaped fireworks. In this article, I introduced how to use the object modelled in Maya as the shape of particles. This approach could be used to create an effect with a unique shape. How to upload assets from Unity to STYLY. Read this article.