Houdini 20.5 Nodes VOP nodes

Karma Pyro Fire Emission VOP node

Creates emission to control the emission component of volume shading used for fire.

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This node expends the Karma Pyro Fire Color with an additional masking option that can directly drive the emission component of the Karma Volume node.

This node is intended as a building block for building larger volume shader.

Overview

Parameters

Intensity

Intensity Scale

Sets the emission intensity for the fire. Increase this value to make the fire brighter. Set the menu on the right side of this parameter to Use Ramp to remap the intensity.

Source Range

The minimum and maximum source values to map to the left and right endpoints of the Fire Intensity Ramp. Increase the minimum source value to reduce the emissive parts of the volume.

By increasing the minimum value from zero, the area of the fire will shrink (Enable Mask is turned off).

Fire Intensity Ramp

Controls how the raw Intensity Volume values are mapped to effective intensity. The horizontal axis of this ramp spans Source Range.

Color

Color Mode

Sets how the color is calculated for the fire. Color Ramp will map the colors using Fire Color Ramp from the given Source Range. Choose Physical Blackbody or Planck Backbody to compute color based on the temperature of an incandescent blackbody.

Note

Planck Blackbody incorporates emission power into the calculated color. The power scales rapidly at high temperatures, so you might need to reduce emission intensity to compensate. To use the pure physical blackbody color, set emission intensity to constant 1.

Source Range

The minimum and maximum source values to map to the left and right endpoints of the Fire Color Ramp.

Fire Color Ramp

Controls how the Color Volume values are mapped to emission color. The horizontal axis of this ramp spans Source Range.

Temperature Scale

Scale applied to the Color Volume values before they are mapped to blackbody color.

Masking

Enable Mask

Masks the emission based on the Mask Volume using a threshold range. Mask Center and Mask Width control the masking range. By default, where the mask volume is at the minimum and maximum of this range, the additional emission multiplier is 1 and 0, respectively. Emission is reduced in areas where the mask value is larger. Masking is useful for bringing out crunchy details for an explosion.

Scatter with and without masking.

Mask Center

In conjunction with Mask Width, this parameter controls the range of values used for masking emission. The effective range of mask values is from Mask Center - Mask Width * 0.5 to Mask Center + Mask Width * 0.5. When set to a lower value, more of the emission will be masked and the explosion will glow less brightly. When set to a higher value, the volume will appear to glow internally, with this glow peeking through cracks in the smoke.

The video shows the effect of increasing this parameter while keeping Mask Width fixed.

Mask Width

Controls the range of values used for masking emission, in conjunction with Mask Center. The effective range of mask values is from Mask Center - Mask Width * 0.5 to Mask Center + Mask Width * 0.5.

Use Mask Ramp

Use a ramp to set how the emission changes between the minimum and maximum mask threshold (as set by Mask Center and Mask Width).

Mask Ramp

Sets how the emission changes between the minimum and maximum mask values (as set by Mask Center and Mask Width). White means full emission and black means no emission.

Note

The default white to black ramp will produce the exact same results as having Use Mask Ramp turned off.

When the ramp is set white to black from left to right:

When the ramp is set black to white from left to right:

Bindings

Intensity Volume

The name of the volume to be used for the intensity of fire.

Color Volume

The name of the volume to be used for the color of fire.

Mask From Geometry

When turned on, use the mask volume (given by Mask Volume) as the mask source. Otherwise, use the maskvolume input connection on the node.

Mask Volume

The name of the volume used to generate the mask volume.

Alpha From Geometry

When turned on, use the alpha volume (given by Alpha Volume) as the alpha volume source. Otherwise, use the alphavolume input connection on the node. If nothing is connected, it will default to 1.

Alpha Volume

When Enable Mask is on, the emission is multiplied by this volume.

See also

VOP nodes