Manual Modules Dynamics Force Fields Gravity
Gravition Object Basic Coord. Shape Falloff FieldShape
The field will usually exert a force on any object that are inside the shape (provided that Exclusion is disabled — see Exclusion, below).
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| A field can take one of the following shapes (left to right, top to bottom): unlimited, cube, sphere, cylinder, cone, torus. |
The Torus shape is particularly useful for generating circular motion. This can be achieved by using a Radial field with Exclusion enabled. In additional, the object should be given a starting velocity (v0) that is tangential to the torus pipe cross section.
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| Some example sweeps: 120° sphere, 90° cylinder, 90° cone, 270° torus. |
The default Sweep value is 360°, which corresponds to the entire shape. To restrict the field to just a section of the shape, enter a value less than 360°. For example, to define a hemispherical field, set Shape to Sphere and Sweep to 180°.
You can enter a value only if Shape is set to Torus.
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| A torus shape with radius set to 10%, 40% and 100%. |
This option is enabled by default. When it is enabled, the field will exert its force outside the shape as opposed to inside.
One possible usage is to allow the field to capture objects — when an object leaves the shape, a force can be exerted that will pull the object back towards the shape.
This enables you to offset the shape of the field away from the origin. This is useful with the Radial field only, where the origin defines the source of attraction or repulsion. By using the Offset values with the Radial field, you can effectively move the source of attraction or repulsion away from the centre of the shape.
Here the Offset parameters have been used to move a radial field’s spherical shape away from the origin. Provided that Strength is set to a positive value and Exclusion is disabled, objects inside the shape will now be attracted towards the bottom left rather than towards the centre of the field. This is because the origin defines the centre of attraction or repulsion.
A falloff (Falloff tab) will always refer to the field’s origin, not to the centre of the shape. This is explored in the diagram below.
Two small white spheres, both moving to the right, are about to enter a Radial field whose Shape is set to Cube. Of the two spheres, the one on the left will experience less force. Due to the offset shape, the left-hand sphere will pass through the edge of the falloff (dark sphere) only.
In the diagram above are two Radial fields with Shape set to Cube. The shape of the left Radial field has been offset above the origin. Note how the left field’s falloff (dark sphere) is not offset but instead remains centred on the origin. Apart from the shape offset, the two Radial fields are identical.
When the two spheres (travelling from left to right) enter their fields, the left sphere will experience much less force than the right sphere. Although the left sphere will pass through the centre of the shape, it will pass through the edge of the falloff and experience only a fraction of the full force. The right sphere will experience more force than the left sphere because it will pass through a field region with less falloff.
Here you can set the dimensions of the field numerically. Alternatively, use the Scale tool to resize interactively in the viewport.