Modulating texture values

How to use utility VOPs to modify textures in your materials.

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Overview
Example
Other nodes

Overview ¶

When building shaders in VOPs, you’ll often want to modify the output of nodes to suit your needs.

Example ¶

In this example, a Principled Shader has been applied to a sphere. It’s roughness input is connected to a Surface Color VOP with a black & white checkerboard texture. The luminance VOP isn’t strictly necessary, but makes it easier to work with the values later on.

This results in perfectly sharp reflections where the texture values are black and extremely dull reflections where they are white.

In the figure below, the left side shows the rendered results, the right side shows the roughness values

You can use a Fit Range VOP to modify the value range of the texture. This allows you to tweak the range of roughness values without having to modify your texture.

Tip

You can create the Fit Range VOP using the Shader Effects menu, MMB on the rough input to bring this up, then LMB Filter > Fit. This will automatically promote the range inputs to the parent SHOP.

We’ll leave the Source Min at 0 and Source Max at 1. We’ll set Destination Min to 0.3 and Destination Max to 0.6. This maps texture values of 0 to an output value of 0.3 and texture values of 1 to an output value of 0.6. Anything in between is interpolated linearly.

As you can see below, this leads to a much more subtle variation in roughness. Tools like this make it quick and easy to tweak the final result without going back to texture painting.

Other nodes ¶

The following are some nodes you may find useful for this type of filtering.

Mantra materials

Using materials ¶

Using materials

How to assign assign materials and use the library of built-in materials.
Material palette

Lets you assign materials to objects and primitives interactively.
Overriding material parameters and properties

How to change material parameters on individual objects or pieces of geometry.
OpenGL Shaders

How to customize how materials appear in the OpenGL viewport.
Material code caching

You can pre-compile a material as a digital asset to speed up shader compilation at render time.

Textures and UVs ¶

Creating materials ¶

Building materials

The basics of how to create, combine, and modify materials in Houdini.
Layering shaders

How to mix and layer two or more materials together to create a combined material.
Material parameters

How to build a parameter/input interface for your custom material.
Working with VOPs

Tips for working with shaders in the VOP network.

Guru level ¶

Material exports

How to export extra information from the shader and save it as part of the rendered image.
Absorption and nested dielectrics

Automatically scoop out geometry with one shader from inside overlapping geometry with another shader, allowing different shading properties inside.
Material stylesheets

Material stylesheets are a highly technical solution for assigning materials and overriding material parameters on packed geometry.
Loops and conditionals in VOPs

How to create looping and conditional blocks of nodes in VOP networks.
Writing a custom viewport shader in GLSL

Other renderers ¶