By Hammer Chen, Kristin Ivanova

Final animation

Here I modeled a solid geometry for a car with many parts. It contains all the essential components for a typical car from exterior to interior. You can replace those low-poly gears with high poly in real production.

The car interior is basic. It's needed only so when it explodes, to have something burning on the inside. 

The car dynamics are constructed by using tP joints helper in combination with the ShapeCollision operator. For example, for the front left wheel, it is constrained by using a TP Joint SC Helper, type set to Spring. The strength of the car suspension can be controlled through Spring, Damping, and Friction parameters.

Let's take the car doors as another example. The car_front_L_door is constrained to the car_body through TPJoint - Hinge. Make the car door breakable by enabling the Breakable option. All four doors are constrained by their TPJoint helpers; we can decide which doors to fly away due to the explosion by tweaking those joints individually.

To make the explosion directable, we place some geometries inside of the car as sources for particle emitters. For example, the Sphere_core_002 is put under the engine hood. In the tP's dynamic set, it is added  to the MatterWaves operator. Then the Major_Explo_2 particles emit from the Sphere_core_002. Since the direction of particles is based on the surface normal of the Sphere_core_002, we can easily adjust the angle of explosion by transforming the Sphere_core_002 geometry, without any complex mathematical formulation.

Directability is very important in every FX setup. Not only can we decide where the center of an explosion is, we can also control when to trigger the blasts. The screenshot above shows the two explosions controlled by Time Interval condition in tP. In this car explosion animation, the first blast happens at frame 44, then is followed by a smaller blast at frame 100. Through that degree of control over the particles, we can orchestrate the explosion both spatially and temporally.

Variation in the smoke color can enhance visual realism. That's why we generate two sets of dust particles (v_dust_A and v_dust_B), each one used for two Fire/Smoke sources that are set to different RGB colors. Again, this idea is borrowed from the Artillery Explosion tutorial.

The screenshots above show the dynamic sets for particles as Fire/Smoke emitter nodes. First, particles are generated from the surface of any given geometry (car seats for example). Then, when the car explodes, the particles continue to emit from the car seats even when the seats are in mid-air.

It can be very tricky to make both fire and explosion look good in the same scene. You tend to get over-exposure in the fire or under-exposure in the explosion and vice versa. The key is to find an optimal value for the fire and explosion's temperature, in combination with the Color Ramp and Curve in the Volumetric Render Settings of a Fire/Smoke Simulator. In this case, set the Temperature for the fire source to 1800.0 and 4000.0 for the explosion source. I find those values are pretty optimal for both fire and explosion, maintaining all the details in the rendering without clipping too much.

See how temperature from the fluid source plays an important role in the proper exposition of the fire. When the temperature is set to 1800, it shows more details in its hottest parts.