Sample Signed Distance Field

Menu Path : Operator > Sampling > Sample Signed Distance Field

The Sample Signed Distance Field Operator allows you to fetch a distance field stored in a Texture3D.

A Signed Distance Field (SDF) determines the distance from a point in space to the surface of a shape. By convention, this function is negative for points inside of the shape, and positive outside. The SDF is equal to zero on the surface of the object.

Operator Properties

Input	Type	Description
texture	Texture3D	The 3D texture that stores the SDF.
position	Position	The position to sample the SDF from.
orientedBox	OrientedBox	The oriented box that specifies the transformation to apply to the SDF.
Level	float	The mipmap level.

Output	Type	Description
distance	float	The signed distance from the position to the surface the SDF defines. This value is positive when position is outside of the shape and negative when position is inside the shape.
direction	Vector3	The direction that points to the closest point on the surface the SDF defines.

Additional notes

You can set the position, orientation, and scale of the SDF using an OrientedBox. The center of the OrientedBox corresponds to the center of the sdf.

Limitations

For this Operator to output correct distances in world coordinates, the dimensions (size) of the OrientedBox must match the dimensions of the box you used to bake the SDF. If you do not set this up correctly, distances from inside and outside of the texture bounds have a different scale, which means the output does not exhibit the expected behavior.

Also, if you apply a non-uniform scale to the sdf (i.e. not proportional to the dimensions of the box you used to bake it), this results in distorted distances.