hou.Ramp class

A Ramp represents a function that yields either floating point values or colors. You can evaluate this function between 0.0 and 1.0, and the function’s shape is determined by a sequence of values at key positions between 0.0 and 1.0.

See also: spline

If you evaluate a ramp parameter on a node, Houdini will return a Ramp object.

Methods

__init__(self, basis, keys, values) → float

basis

A sequence of hou.rampBasis values, one for each key. The ramp basis for a key determines how Houdini interpolates from the key up until the next key. If there is no next key, Houdini will hold the value constant until the end of the domain, regardless of the ramp basis.

keys

A sequence of floats, one for each key, each between 0.0 and 1.0, inclusive. Each key represents the location in the domain of its corresponding value.

values

A sequence of values, where each value corresponds to a key. When asked to evaluate at a value where there is no key, Houdini will interpolate between adjacent values using the basis function for the key on the left.

This sequence is either a sequence of floats or a sequence of triples of floats. In the former case, the newly-created ramp will evaluate to a single floating-point value. In the latter case, it will evaluate to a color.

Raises hou.InvalidSize if the keys and values sequences are not not same size, or if values contains subsequences of floats that are not 3 elements long.

>>> lin = hou.rampBasis.Linear

# Create a ramp that linearly interpolates between 2.5 and 4.5.
>>> r = hou.Ramp((lin, lin), (0, 1), (2.5, 4.5))
>>> r
<hou.Ramp is_color=False num_keys=2 data=((t=0, 2.5), (t=1, 4.5))>
>>> r.lookup(0.0)
2.5
>>> r.lookup(0.5)
3.5
>>> r.lookup(1.0)
4.5

# Create a color ramp that linearly interpolates from black to red.
>>> hou.Ramp((lin, lin), (0, 1), ((0.0, 0.0, 0.0), (1.0, 0.0, 0.2)))
<hou.Ramp is_color=True num_keys=2 data=((t=0, rgb=(0, 0, 0)), (t=1, rgb=(1, 1, 1)))>

isColor(self) → bool

Return True if this is a color ramp, and False if it is a single float ramp.

colorType(self) → colorType

If this is a color ramp, return the color space that is used during interpolation. The default is hou.colorType.RGB.

Raises hou.OperationFailed if this ramp is not a color ramp.

setColorType(self, hou.colorType)

If this is a color ramp, set the color space that is used during interpolation. The default is hou.colorType.RGB.

To obtain a more perceptually uniform interpolation, use hou.colorType.LAB. To obtain a ramp that matches the rainbow, use hou.colorType.HSV.

Raises hou.OperationFailed if this ramp is not a color ramp.

lookup(self, interpolant) → float or tuple

Return th value of the ramp at a specified position from 0.0 to 1.0, inclusive.

Returns a float (for floating-point value ramps) or a tuple of 3 floats (for color ramps).

basis(self) → tuple of hou.rampBasis enum values

Return a tuple of hou.rampBasis enumeration values that determine how Houdini interpolates between the keys in the ramp. See hou.Ramp.__init__ for more information.

keys(self) → tuple of float

Return a tuple of floats between 0.0 and 1.0 containing the ramp key positions. See hou.Ramp.__init__ for more information.

values(self) → tuple of float or tuple of tuple of float

Return a tuple of floats (for a float ramp) or a tuple of tuples of 3 floats (for a color ramp) corresponding to the values in the ramp stored at each key. See hou.Ramp.__init__ for more information.