Houdini 17.0 Nodes VOP nodes

Normal Falloff VOP node

Generates a falloff value based on the relationship between the normal and incident vectors.

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This VOP uses the dot product of a surface normal and an incident vector to calculate the falloff value for curved surfaces. The return value will be one (1) where the normal and incident vector line up (parallel), and zero (0) where they are at right angles (perpendicular). This does not work on flat surfaces, since there is no variance in the relationship between the normal and incident vectors with flat surfaces. This VOP can be used to create glow effects, simply by multiplying it with a glow color and applying it to a sphere; or to soften edges by multiplying with the opacity. If inverted, it can be used to create an inexpensive Fresnel effect by multiplying it with the output color of an environment map;

Inputs

nN

The normal vector used in the calculation of the falloff.

nI

This is the incidence direction ray used in the calculation of the falloff.

exp

A floating point value used as the exponent in a power function

invert

This toggle will invert the result. This is useful for creating glows.

facefwd

This toggle will force the normal to face the camera.

Outputs

float

This is the amount of falloff.

Examples

The following examples include this node.

RampReference

This example demonstrates the use of ramps and referenced ramps which are animated over time.

FirePit Example for Material shader node

Note

No geometry is animated in this file. All animation is achieved by animating the textures

Flames are grids so that UV textures can easily be applied, they are then warped around a metaball using a magnet SOP. The flames are then assigned to either a yellow or blue Flames texture. The Flames' opacity mask wrap is set to Decal to prevent the texture from repeating and showing a single pixel ring at the top of the flame geometry. I'm also using a mask file named flameOpacMap.jpg to enhance the flames' shape at the top. The noise offset has been animated over $T with an greater emphasis on the Y axis so that the flames look like they are rising. This is the same reason the Noise jitter is larger for the Y axis as well.

The coals are spheres that have been copy stamped onto a deformed grid. Using Attribute Create surface nodes I am able to override and copy stamp the lava texture’s parameters at the SOP level so that local variables, such as $BBY, can be used to animate the texture. This way the texture’s crust and its crust values can be used only to form the tops of the coals. This reserves the lava aspect of the texture to be used on the bottoms of the coals. The lava intensity (Kd attribute) is then stamped and animated to create the look of embers on the bottom of coals glowing.

See also

VOP nodes