# Learning Expedition 0001: Cast Modifier

Back when I was in c4d land I started several “Learning Expeditions.” I thought it might be fun to do the same with Blender and this community. It’s a bit of a random start, but first up is the “Cast” Modifier.

This thread will be a series of posts with screen grabs, animations, and perhaps some shared files. As I’m certainly not the ultimate expert I welcome the contributions of others.

The cast modifier distorts a model, pushing the polygons towards three shapes: spherical, cylindrical and cubic.

This first screen grab shows how this modifier might be used in character design. Here are examples where I’m using only the cast modifier and a subsurf modifier. In some instances I used multiple instances of those two modifiers, but nothing else. Here I never sculpted or modified the Suzanne model in any other way.

Much more by way of explanation and samples to come in subsequent posts…

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The cast modifier can of course impact an entire object uniformly.

But Blender also provides three ways to constrain the effect to targeted parts of a model.

You can limit the impact by axis. You can use a saved vertex group, or you can use the influence of an external object.

The density of the mesh has some effect when the factor is small, but massive effect when the factor significantly exceeds 1.0.

Here do note the the starting resolution of these cubes.

Again the resolution impact may be modest at low factors (Here all with factor of .4)

But when the factor is raised beyond 1, surprising differences emerge. (Here factor 2)

And here factor 5:

Note: With very modest mesh density the modifier might not work at all or not as expected.

Here a low poly cube is “spherized” by the cast modifier. Because this animation takes the factor far beyond one, the shape is manipulated past a spherical form into something “hyper-spherical”. I don’t claim to understand exactly what is happening in that “hyper” form, LOL.

Tomorrow we’ll get to some more practical uses, but it’s valuable to think for a second or two about positive and negative factor.

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So we now learn about Suzannes family members…

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I was thinking the same while playing with the modifier. The eccentric uncle, the overweight aunt…the skinny cousin…

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The cast modifier can work great for mounding, recessing or bubbling. You will want to select an object in the modifier slot to position where the protrusion/recession occurs.

Note: if this object has the same z position as the source object you will see no effect at all.

Here in a little “bubbling soup” animation I am using 4 instances of the modifier with 4 different objects. Obviously a complete version would likely need more bubbles to complete believability and sizes would need refinement.

To achieve the look I hid the reference spheres and also tweaked the timing so that the collapse of the bubble occurs much faster than the bubbles formation.

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Utilizing an object in the optional cast modifier slot doesn’t effect the shape or size of the distortion…only the location. You can only choose spherical, cubic and cylindrical.

Here is what happens as you raise/lower the modifying object. Again there is zero effect when the z/normal locations are the same.

Still to come…another example use or two, and a few more notes/observations.