..::dissolving planet::..

The way we’re going to handle this task it is by subtracting the geometry from the main Earth planet – a Geosphere using a Boolean Compound Object, with an animated operand. This means the object we’re using to subtract the geometry from the Earth model is being transformed in some way to create an animated subtraction.

The subtraction is another clone of the Earth model which is scaled down, a noise modifier added to distort the mesh (to create the irregular shaped cracks in the surface) and repositioned to one side of the Earth model. This ensures that one side will begin to disintegrate first, spreading across to the other side as the subtraction sphere is scaled up. If the sphere is animated scaling from a low (about 30% of the original) to a high (around 120%) over a series of frames, the resulting subtraction will give the impression that the surface is dissolving.

To reveal a glowing mass, we need to create one. This is quite simply a clone of the Earth’s sphere with a smaller radius. To create the glow, we assign a material ID to a new material which we have set up to self-illuminate a light yellow colour and assign it to the new sphere. The glow it’self is a render effect which is set so it only affects the ID assigned to the glow material. If another material is assigned to the subtraction sphere before the Boolean, then it too can have a glow performed on it, which can create different coloured glows as the surface is being dissolved. To top it all off, we will add a volumetric Omni light to shine through the gaps in the surface.

Finally, one thing to note. Before any Boolean object is created, ensure that your animation and materials are set up in advance, else assigning materials to the Boolean result may not work as expected. Work with low polygon objects at first, especially the subtraction object; you can always increase the detail later on if your computer can handle it! Finally, before you render, perform a preview to make sure the Boolean is performing correctly on every frame. Animated Booleans can fail, which results in flickering on the geometry. If this occurs, amend the geometry count of the subtraction sphere or the intensity of it’s Noise modifier and perform another test.

	Create the initial Earth Geosphere at 0,0,0 with 10 Icosa segments and a Radius of 100. Clone this and label it “Glow”. Set the Glow sphere’s radius to 98. Assign a self-illuminated material with a material ID of 1 to the Glow and assign an Earth material to the Earth sphere, setting up any additional mapping to the sphere if required at this stage.
	Copy the Earth sphere again and label it “Subtraction”. Scale it down to approx 30% and offset it to the left hand side of the Earth sphere. Animate the scale up to 120% over 500 frames. Add a Noise modifier to the stack and use the settings illustrated. Create a new material with an ID of 1 and assign it to the Subtraction sphere.
	Select the Earth sphere and create a new Boolean Compound Object. Ensure subtraction A-B is selected and select the Subtraction sphere as Operand B. Select “Match Material ID’s to Material” if prompted. Create an Omni light and position inside the “cavern” inside the Earth sphere created by the Boolean. Use the settings for this, and it’s volumetric light, as illustrated.
	Finally, we add the glow. Create a Lens Effect rendering effect and add a Glow element to the right-hand Parameters column. In the Options tab, check on Image Sources - Effects ID (already set to 1). Set the Size to 0.05 and the Use Source Color to 100. If required, add another glow element with a lower intensity and higher Size to create a diffused glow around the glowing areas.
	The final render. Additional elements such as debris could be set to be emitted from the cracks in the Earth model to give a more dramatic effect if desired.
	Zip file to accompany

Initially published: Computer Arts magazine, Issue 80, February 2003.

Copyright © Pete Draper, February 2003. Reproduction without permission prohibited.

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