1. Single explosion:

   • Single burst method uses a single input point to generate a burst. This can be used for a single fireball or a smaller explosion.

     

   • Multi burst method uses multiple input points to generate multiple bursts for a single explosion (3-4 points are recommended). The input points should be scattered in a relatively close distance to each other, and their startframe values should also differ by a couple of frames to prevent all of the bursts from triggering simultaneously.

     Compared to single burst, this method can create more interesting explosion shapes.

     

2. Consecutive explosions:

   • Consecutive multi burst method uses multiple clusters of points to represent each explosion. Each cluster should contain 3-4 points, same as the multi burst method. The startframe attribute values for points inside a cluster should be very close to each other with only a couple of frame difference, while the average startframe value for each cluster can vary to time the explosions. In this case, you may want to run each explosion as a separate pyro simulation.

     

A burst is made of replicated clusters of points or what we call burst components. Each burst component represents a source attribute for pyro simulations. For each component, one of the following source attributes can be selected, which creates the corresponding point attribute.

• Density (density), represented as grey color.

• Temperature (temperature), represented as blue color.

• Divergence (divergence), represented as orange color.

• Burn (burn), represented as yellow color.

• Color (Cd), which you determine.

• Alpha (Alpha), represented by purple color.

The output of this node will be a mix of burst components, each responsible for sourcing its own specified attribute. These attributes should be rasterized into volumes using the Volume Rasterize Attributes SOP, at which point they can be sourced into a pyro simulation. The Source Attribute (source_name by default) is created on points to ensure that each component only contributes to rasterization of its own attribute. For example, the temperature attribute will be set to 0 for points from the burn component, so using these burn points during temperature rasterization would lower the values in the final source volume.

The velocity (v) attribute is a special exception. By default, v is appended to the Source Attribute of each point, signaling that all points should be used when rasterizing the velocity field. You can use Cull Velocity in the Quick Setups menu if you prefer to have only one burst component contribute to velocity rasterization.

Choosing the Simulated Debris menu option from the Quick Setups dropdown on the Pyro Scatter from Burst node will automatically generate a small setup that emits debris flying out from the center of the explosion. The emitted debris are very simple geometries that can be replaced by your own, more detailed version. The pieces are then simulated using the RBD Bullet Solver.

Choosing the Simulated Sparks menu option from the Quick Setups dropdown on the Pyro Scatter from Burst node will generate a small setup that emits sparks flying out from the center of the explosion.

Video credit: Moeen Sayed

Trails can be differentiated based on the shape of their path.

1. Ballistic Trails are long lived trails that are pulled down by gravity, creating arced paths.

   

2. Straight Trails are short-lived trails that shoot out from the core of the explosion. These projectiles are ejected out of the blast with a force that exceeds gravity; therefore, they have no arc. Usually they are thin trails, with hundreds of particles shooting out at once.

   

Curl, spiral, and noise deformations can be applied on the generated paths to simulate spinning out trails. In some cases, the projectiles could shoot out on a spiral path, but as they move further away, the spiral dampens and the trail becomes a smoother arc. You can apply any deformation to the path curves following this node.

There are two trail nodes that are often used together: Pyro Trail Path and Pyro Trail Source.

Pyro Trail Path computes the ballistic trajectories of the projectiles that get thrown out of the explosion, which you can visualize by the curves. This node also lets you control the shape of the curves.

Pyro Trail Source uses the output of Pyro Trail Path to generate the point sources that travel along the curves.

There are two ways to incorporate trails into your explosion workflow. You can either merge the trail node stream before or after the Pyro Solver, depending whether or not you want them to interact with the simulation. If you merge the two streams before the solver, attributes such as velocity will be added during simulation. Merging the streams after the solver will result in more perfect looking (less distorted) trails, since any physics from the explosion won’t affect the paths.