Microphone object

The Microphone object specifies a listening point for the SpatialAudio CHOP.

The Microphone object specifies a listening point for the SpatialAudio CHOP. Multiple microphones can be used by one SpatialAudio CHOP to create stereo or surround sound, with special effects like the doppler effect, volume loss over distance, obstacle interference, atmospheric filtering and positional audio.

To set up a Spatial Audio scene, one or more Sound objects should be used to emit sound. At least one microphone is needed to capture the sound. A SpatialAudio CHOP is needed to render the sound. If any obstacles or filters are used, at least one Acoustic CHOP is needed to design the spectrum filter.

Moving Sound and Microphone objects around will produce variations in pitch and volume, especially if either object is directional. Setting up a directional microphone or sound object is much like setting up a directional light.

Parameters

Transform

Keep Position When Parenting

When the object is re-parented, maintain its current world position by changing the object’s transform parameters.

Pre-transform menu

This menu contains options for manipulating the pre-transform values. The pre-transform is an internal transform that is applied prior to the regular transform parameters. This allows you to change the frame of reference for the translate, rotate, scale parameter values below without changing the overall transform.

Clean Transform

This reverts the translate, rotate, scale parameters to their default values while maintaining the same overall transform.

Clean Translates

This sets the translate parameter to (0, 0, 0) while maintaining the same overall transform.

Clean Rotates

This sets the rotate parameter to (0, 0, 0) while maintaining the same overall transform.

Clean Scales

This sets the scale parameter to (1, 1, 1) while maintaining the same overall transform.

Extract Pre-transform

This removes the pre-transform by setting the translate, rotate, and scale parameters in order to maintain the same overall transform. Note that if there were shears in the pre-transform, it can not be completely removed.

Reset Pre-transform

This completely removes the pre-transform without changing any parameters. This will change the overall transform of the object if there are any non-default values in the translate, rotate, and scale parameters.

Transform Order

The left menu chooses the order in which transforms are applied (for example, scale, then rotate, then translate). This can change the position and orientation of the object, in the same way that going a block and turning east takes you to a different place than turning east and then going a block.

The right menu chooses the order in which to rotate around the X, Y, and Z axes. Certain orders can make character joint transforms easier to use, depending on the character.

Translate

Translation along XYZ axes.

Rotation

Degrees rotation about XYZ axes.

Scale

Non-uniform scaling about XYZ axes.

Pivot

Local origin of the object. See also setting the pivot point .

Uniform Scale

Scale the object uniformly along all three axes.

Look At

Object to point to. Constrains an object so its -Z axis always points at another object’s origin.

Look At Up Vector

When specifying a look at, it is possible to specify an up vector for the look at. This controls the roll of this object when looking at the look at object.

Don’t Use Up Vector

Use this option if the look at object does not pass through the Y axis of this object.

Use Up Vector

This precisely defines the direction of the Y axis of this object while looking. The up vector specified should not be parallel to the look at direction. The value used is specified by the Orient Up Vector parameter below.

Use Quaternions

Quaternions are a mathematical representation of a 3D rotation. This method finds the most efficient means of moving from one point to another on a sphere.

Path Object

A reference to the curve node or object you want this object to follow.

Roll

The orientation of the object around the path.

Position

The position of the object along the path. 0.0 means at the beginning of the path, and 1.0 means the end. The integer portion of the position is used as the primitive number inside the geometry while the fractional part indicates the u value on the primitive.

If the primitive number does not exist, then it is wrapped back to the beginning. So for numbers greater than 1.0 in a path object that only have a single primitive, it wraps around to the beginning again. You can easily animate something moving around a circular track simply by continuously increasing the position value.

Keyframe this value to animate the object moving along the path.

Note

The Follow Path tool on the shelf automatically sets keyframes on this parameter that you may want to edit or replace.

The Parameterization option controls how position values between 0 and 1 correspond to knots on the path curve.

Parameterization

Controls how the Position parameter is translated into a point on the path curve. Use Arc-length (the default) to interpolate the position values evenly along the physical length of the curve.

Use Uniform to distribute the position values between the knots of the curve. This lets you slow down the object at certain points by bunching up knots in the path curve. However, it is much more convenient to simply edit the animation curve to control the speed of the object along the path.

Orient Along Path

Orient the object according to the path’s curvature.

Orient Up Vector

The direction vector of the object’s Y axis to orient with.

Auto-Bank factor

Controls automatic banking of the object as it turns corners. Set this to 0 to turn automatic banking off.

Microphone

Microphone Active

Turns the microphone on (if greater than zero) or off.

Sensitivity

The volume gain of the microphone.

Directional

If off, the microphone is non-directional and accepts sounds from all directional equally. Otherwise, the microphone is directional and pointed down the negative Z axis. The recording cone and outer cone parameters determine the field of recording. Any sounds within the recording cone have a gain defined by the sensitivity (above). Any sounds outside the outer cone have a gain defined by the outer sensitivity parameter (below). Any sound between the recording cone and the outer cone have a gain that is interpolated between the two sensitivities.

Recording Cone

Defines the angle of the recording cone, measured from the Z axis to the edge of the cone. Setting this to 180 degrees will make a non-directional microphone.

Outer Cone

Defines the dropoff region from the recording cone to the outer cone. If the recording cone is set to 60 degrees and the outer cone is set to 20 degrees, any sounds coming from more than 80 degrees off the Z axis will fall outside the outer cone.

Dropoff

Sets the interpolation type for the dropoff from the recording cone sensitivity to the outer sensitivity.

Dropoff Rate

Increases or decreases the rate of dropoff.

Outer Sensitivity

The gain that is applied to any sounds coming from outside the outer cone.

Filter CHOP

Specifies an optional CHOP that defines the frequency response of the microphone. The filter should be a channel named “absorb”, designed by an Acoustic CHOP.

Misc

Set Wireframe Color

Use the specified wireframe color

Wireframe Color

The display color of the object

Viewport Selecting Enabled

Object is capable of being picked in viewport.

Select Script

Script to run when the object is picked in the viewport. See select scripts .

Cache Object Transform

Caches object transforms once Houdini calculates them. This is especially useful for objects whose world space position is expensive to calculate (such as Sticky objects), and objects at the end of long parenting chains (such as Bones). This option is turned on by default for Sticky and Bone objects.

See OBJ cache preferences for how to control the size of the object transform cache.

Usages in other examples

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