Houdini 17.0 Nodes VOP nodes

If-Then Block VOP node

Contains other VOP operators.

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This operator contains other VOP operators. The code for the contained operators is executed only if the value fed into the first input matches the criterion specified by the Condition parameter. At least one input must be connected to this operator.

Use this operator when you want something to happen only if a certain condition is met. The Condition Value is usually the output of a Compare operator, but any integer value can be used.

Any value that you wish to modify inside the If-Then Block operator must be provided as an input. The outputs of the If-Then Block operator will contain the modified versions of the inputs (if the condition was met) or the unmodified version of the inputs (if the condition was not met). The actual values wired into the If-Then Block operator inputs are never modified, and so can be connected to other operators in the network, but remember that the values from these operators will always be the values unmodified by the If-Then Block operator.

There is no place in this operator to specify what should happen if the condition is not met (i.e. an Else block). To achieve the same effect as an if-then-else statement, use two If operators. Connect the same output value to both Condition Value inputs of the two If-Then Block operators. Then set the Condition parameters of the two If-Then Block operators to be different. At this point one If-Then Block operator represents the "if" block, and the other represents the "else" block. Then connect your inputs to the "if" block operator. Then connect all but the Condition Value output from the "if" block into the inputs of the "else" block. Now the outputs of the "else" block are going to be what you would expect from an if-then-else statement. For simple if-then-else constructs, use the Two Way Switch operator instead.

Parameters

Condition

Specifies the condition that must be met by the first input for the contained code to be executed. Either the input value must be False (equal to 0) or True (not equal to zero).

Inputs

Condition Value

This integer input must be connected. The value connected to this input is compared to the requirements of the Condition parameter. Usually this input will be connected to the output of a Compare operator, or one of the logical operators (And and Or).

Next Input

Up to 64 inputs can be connected here. Each time an input is connected, a new input slot is added. All connected inputs mimic the properties of the output wired into them. They adopt the same help label and name as the output connected to them. If multiple outputs with the same name are connected, the names of the inputs are automatically incremented to make them unique.

Outputs

The list of outputs depends on the inputs connected to the Subnet Output operator contained in this operator. The data type and name of each output will match the corresponding input of the Subnet Output operator.

Examples

ST_Colour

This is a simple example of using the If-Then Block VOP with the "true" value coming from outside the If-Then subnet, and the "false" value also coming from outside the If-Then subnet.

A Condition VOP is used based on the "t" Global Variable. When "t" is less then .5, the If-Then gets a "false" Condition, and when "t" is equal to or greater than .5, the If-Then gets a "true" Condition.

In this example, the red color is used if the value fed into the condition is not True, and blue if the condition being fed in is True.

SimpleInsideSubnet

This is a very simple example of using the If-Then Block VOP with the "true" value coming from outside the If-Then subnet, and the "false" value coming from inside the If-Then subnet.

In this example, the red color is used if the value fed into the condition is not True, and blue if the condition being fed in is True.

SimpleOutsideSubnet

This is a very simple example of using the If-Then Block VOP with the "true" value coming from outside the If-Then subnet, and the "false" value also coming from outside the If-Then subnet.

In this example, the red color is used if the value fed into the condition is not True, and blue if the condition being fed in is True.

The following examples include this node.

FlipFluidWire Example for FLIP Solver dynamics node

This example demonstrates the use of the Flip Solver and the Fluid Force DOP. The Fluid Force DOP is used to apply a drag force on a wire object according to the motions of a flip fluid. The drag force is only applied at locations where fluid exists in the fluid object.

DiffuseSmoke Example for Gas Diffuse dynamics node

This example demonstrates how to diffuse the density of a smoke simulation using the Gas Diffuse DOP.

grass

This example simulates grass being pushed down by an RBD object. Fur Objects are used to represent the blades of grass and Wire Objects are used to simulate the motion. When a single Fur Object is used to represent the grass, neighbouring blades of grass will have similar motion. Additional objects with different stiffness values can be used to make the motion less uniform. When "Complex Mode" is enabled, two objects are used to represent the grass. The stiffness of each set of curves can be controlled by adjusting the "Angular Spring Constant" and "Linear Spring Constant" parameters on the corresponding Wire Objects.

FluidGlass Example for Particle Fluid Solver dynamics node

This example demonstrates how to get a smooth fluid stream to pour into a glass.

BreakWire Example for Wire Solver dynamics node

This example demonstrates how to break wire constraints on a per point basis. The wire solver is set up to constrain certain points if it finds an attribute named 'pintoanimation'.

MotionVector Example for Mantra render node

The example demonstrates how to generate a motion vector layer for post-velocity compositing. Load the example and render 5 frames. Then in the image viewer, switch from 'C' (colour) to 'motion_vector' to see the results.

RampReference

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

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.

Clumping Example for Fur geometry node

The Fur SOP is used to instance hair-like curves.

In this case, the Fur SOP is used to create curves that can be used for clumping. A second Fur SOP is used to illustrate how to create hairs that use the clumping geometry.

FurBallWorkflow Example for Fur geometry node

This example demonstrates how the Fur SOP and Mantra Fur Procedural can be applied to an animated skin geometry. CVEX shaders are used to apply a custom look to the hairs based upon attributes assigned to the geometry.

FurPipelineExample Example for Fur geometry node

This example illustrates how custom shaders can be used to define the appearance of fur generated by the Fur SOP.

FurTextureMap Example for Fur geometry node

This example demonstrates how to use a texturemap to color fur.

Shaved Example for Fur geometry node

This example demonstrates how to use a texture to control hair density.

ST_Colour

This is a simple example of using the If-Then Block VOP with the "true" value coming from outside the If-Then subnet, and the "false" value also coming from outside the If-Then subnet.

A Condition VOP is used based on the "t" Global Variable. When "t" is less then .5, the If-Then gets a "false" Condition, and when "t" is equal to or greater than .5, the If-Then gets a "true" Condition.

In this example, the red color is used if the value fed into the condition is not True, and blue if the condition being fed in is True.

SimpleInsideSubnet

This is a very simple example of using the If-Then Block VOP with the "true" value coming from outside the If-Then subnet, and the "false" value coming from inside the If-Then subnet.

In this example, the red color is used if the value fed into the condition is not True, and blue if the condition being fed in is True.

SimpleOutsideSubnet

This is a very simple example of using the If-Then Block VOP with the "true" value coming from outside the If-Then subnet, and the "false" value also coming from outside the If-Then subnet.

In this example, the red color is used if the value fed into the condition is not True, and blue if the condition being fed in is True.

SimpleMetaImport Example for Meta-Loop Import VOP node

This example demostrates how to use the Meta-Loop Start, Meta-Loop Next and Meta-Loop Import VOPs.

It calculates the sum of the densities of all metaballs in some input geometry, and uses that total to create an image in a Composite Network.

PointCloudIterateAverage Example for Point Cloud Iterate VOP node

This example shows how the pciterate vop can be used to average together points returned by pcopen. First, a point cloud is generated with a floating point "check" channel initialized to 1 inside a circle in the x-z plane. Then, the points are filtered in a shader by looping using the pciterate vop and averaging the value of the "check" channel. The point cloud used in the example is stored inside the asset as points.pc.

See also

VOP nodes