Making of Fruit Explosion

By Hammer Chen, Kristin Ivanova

In this article, I show how to create a fruit explosion with Phoenix FD for 3ds Max. The fruit explosion consists of two fruits colliding at a high speed, then they smash and their juices splash out.

For the purpose of illustrating this article, we’ve shaded the fruits to get a tomato-ye look. However, the shape and shaders of the two geometries can be customized to your liking to get whatever kind of fruit you want to smash We don’t focus on the shading information of the fruits here..

The most challenging part of this animation is the fruit mesh smashing. Instead of softbody or cloth simulation, I use 3ds Max's Morpher Modifier and keyframe the splitting fruit meshes. I avoid using any softbody/cloth simulation in this tutorial, because it is difficult to control the results. By keyframing the animation, you have full control and are able to add layers of detail.

Since the mesh motion purely relies on keyframe animation, it is crucial to find the right reference footage to align with. You could search for keywords like "high speed fruit" or "fruit explosion." Or you can go through any stock footage sites. Once you find a good footage, load it in 3ds Max. This way, you can align your keyframe animation to the footage in the viewport accurately.

1. Fruit geometry deformation
Based on observation from reference videos, I concluded that one basic fruit mesh and four different deformed meshes would be enough to recreate the fruit splitting effect. Start from modeling the basic shape. The fruit is modified from a simple sphere and the mesh is split as shown in the image above. All other four deformed meshes are derived from this basic mesh. This is to make sure all five geometries have the same topology and can be used as morph targets later.

We duplicate the basic mesh into four other meshes.. By moving the vertices or adding modifiers on top, we create four different deformed fruit meshes: split, bump_shape, dent, and FFD_deformed. These four geometries represent the various stages of changing the shape of the fruit during the collision. Add a Morpher modifier to the basic mesh and load up the four geometries as morph targets.

The above image shows the curves of four morph targets in the Curve Editor. At frame 15, the fruits collide. By mixing the various target shapes, we mimic the smashing effect when the two fruits collide, deform and rupture.

Beside the Morpher modifier, we add a Ripple modifier on top to get subtle oscillations when the fruits collide. Then, we keyframe the Ripple to emulate the effect.To randomize the motion and shape, we add an FFD3X3X3 modifier and set the keyframe to its Control Points. Then, we add a Shell modifier which enables the liquid to collide with the fruit meshes.

Once the single fruit is ready, we duplicate and rotate it, and then slightly shuffle the parameters in the Modifier stacks, so that the two don't look the same.

When the two fruits collide, we have to note that there must be one fruit that pushes the other. In this case, we assume that the fruit on the left side is stronger. We create a Dummy helper in the scene. Both fruits are linked to dummy. When they collide, set the key of the dummy so that the two appear moving together.

Final keyframed animation

2. Fluid Simulation 
Now that the fruit mesh animation is done, we're ready for the next stage - fluid simulation. Let’s put two ring-like geometries inside the two fruits (displayed as See-Through). These two ring meshes are added to the Liquid Source’s Emitter Nodes list.

In the real physical world, the juice (pulp) is packed full inside the fruit and it pops out when they collide. We don’t use the Phoenix FD Properties/Initial Fill to fill the fruit. Initial Fill, provides less control over the liquid leaking problem. Instead, we use a ring-shaped object to emit liquid. This way it is easier to control the fluid, especially when you have a fast-moving object . 

Keyframe the Outgoing Velocity so that it emits liquid from frame 9 and then stops at frame 15. This way we get an intense burst of juice when the fruits collide.

System Unit and Simulation Grid: The Cell size of the Liquid Simulator here is 0.64cm. Enable the Adaptive Grid option. In the real world, regular fruit size is in centimeters range; therefore, we set our 3ds Max System Scene Scale to Centimeter. Our fruit size is 50 cm in diameter. This is one giant fruit. We deliberately make it big because with a large object you get longer distance for fluid and mesh to run, which makes it more manageable when adjusting the effect.

Dynamics: Because gravity is not necessary in this case, let’s set its value to very low. The fruit moves fast, so increase the value of the SPF. I have set the Viscosity and Surface Tension to small amounts to give the liquid a little viscous look. Keyframe the Time Scale, so that we get a bullet-time effect when the fruits explode.

The curve shown is how we keyframe the Time Scale, so after the simulation, we have an exploding fluid that moves slowly over time.

Left: without Mesh Smoothness enabled; Right: with Mesh Smoothness enabled. For Mesh Smoothing, set the Smoothness to 10 and the Particle Size to 0.5.

Fluid simulation results

Final results

Download the Scene files
As a user, I know it's always handy to have the scene when following a tutorial. Here we provide you with the final scene to start with. Please note that the HDR image is not included among the assets in the zip file, so you may find differences with the final images. Feel free to insert your own  HDRI  into the V-Ray Dome light. Click HERE to download. Enjoy!