Houdini 17.0 Nodes VOP nodes

Turbulent Noise VOP node

Can compute three types of 1D and 3D noise with the ability to compute turbulence with roughness and attenuation.

This operator can compute three types of 1D and 3D noise with the ability to compute turbulence with roughness and attenuation:

Perlin noise              (string value "pnoise")
Original Perlin noise     (string value "onoise")
Sparse Convolution noise  (string value "snoise")
Alligator noise           (string value "anoise")
Simplex noise             (string value "xnoise")
Zero Centered Perlin      (string value "correctnoise")

Original Perlin noise is similar to Perlin noise, but marginally less efficient in computation and with different characteristics. The bounds on the noise are roughly (-1, 1) when turbulence is 0.

Perlin noise sums octaves of a noise with range about (0, 1), resulting in a non-zero centered result. Thus the zero centered perlin better matches the ranges of the other noise fields.

Sparse Convolution noise is similar to Worley noise. The noise returned is based on the weights of all of the closest points, with each point’s contribution based on a meta-ball like rolloff curve. That is, if the sample point is close to the sphere, its contribution will be greater. The bounds on the noise are roughly (-1.7, 1.7) when turbulence is 0.

Alligator noise is similar to Worley noise. It is currently not possible to simulate Alligator noise using the Worley functions, but it is possible to get a very similar 'look'. The bounds on the noise are roughly (0, 0.5) when turbulence is 0.

Simplex noise is very close to Perlin noise, except with the samples on a simplex mesh rather than a grid. This results in less grid artifacts. It also uses a higher order bspline to provide better derivatives.

The relative costs for computing noise of different types is roughly:

Cost | Noise Type
-----+-------------------------
 1.0 | Perlin Noise             (see Periodic Noise operator)
 1.1 | Original Perlin Noise
 1.8 | Worley Noise             (see Worley Noise operator)
 1.8 | Periodic Worley Noise    (see Periodic Worley Noise operator)
 2.1 | Sparse Convolution Noise
 2.3 | Alligator Noise

Make sure at least the Position (pos) input is connected in order to notice any noise. The easiest way to accomplish this is to pipe the global variable P into the pos input. All global variables are accessible from the Global Variables operator.

Examples

The following examples include this node.

Street Crowd Example Example for Crowd Solver dynamics node

Crowd example showing a street setup with two agent groups

The setup creates two groups of agents. The yellow agents are zombies which follow a path of the street. The blue agents are living pedestrians that wander around until they come into proximity of the zombies and then they swtich into a running state.

Triggers to change agent states are setup in the crowd_sim dopnet. The zombies group uses proximity to the stoplights and the color of the light to transition into a standing state when lights are red. The living group transition into a running state when they get close to the zombie agents.

Note

The animation clips need to be baked out before playing the scene. This should happen automatically if example is created from Crowds shelf. Otherwise save scene file to a location of your choice and click Render on '/obj/bake_cycles' ropnet to write out the files. The default path for the files is ${HIP}/agents.

FlipColumn Example for FLIP Solver dynamics node

This example demonstrates how a mixture of fluid colours can have their colour changed by a collision with a static object.

CurveForce Example for POP Curve Force dynamics node

This example demonstrates the use of the POP Curve Force node to control the flow of a particle sim AND a flip fluid sim.

Down Hill Lava Flow Example for Material shader node

In this file we create a downhill lava flow with crust gathering and hardening at the base of the slope. All of the animation is achieved through the shader itself, and all of the geometry is completely static.

Note

Most of the parameters for the lava material are overridden by point attributes created in the surface nodes.

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.

StyleDisplacement Example for Material shader node

This is an example file showing an object made up of two quads, one with a bump map, the other with true displacement. This object is duplicated, and the second copy uses a style sheet to reverse the material assignments on the two quads.

RandomMaterial Example for Attribute String Edit geometry node

This example demonstrates how to use the Attrib String Edit SOP to modify String primitive attributes and randomize the colours on a grid on a per-primitive basis.

AlphaOmega Example for Points from Volume geometry node

This example demonstrates how to use a Points From Volume SOP to create a target goal for a flip simulation and make it fill a given piece of geometry.

UnpackWithStyle Example for Unpack geometry node

This example demonstrates the Unpack SOPs ability to evaluate style sheet information while unpacking. Nested packed primitives are used to demonstrate partial unpacking while still preserving styling information. This example also demonstrates the use of a Python SOP to extract information from the per-primitive style sheets.

WornMetal Example for Curvature VOP node

This example shows how the curvature vop can be added to a shader network to add a worn or distressed look to your material.

See also

VOP nodes