Table Of Content
- The Redshift SHOP Node
- Output VOP Nodes
- Shader VOP Nodes
- Material SHOP HDAs
- Houdini 16.0 VOP-Based Shaders
The Redshift SHOP Node
The Redshift for Houdini plugin adds to Houdini a whole new set of VOP nodes to support all the Redshift shading nodes. The Redshift materials and the light shaders are created within Redshift Network SHOP nodes. In the /shop context, Tab->Custom->Redshift Network creates an redshift_vopnet node. Double clicking or pressing “I” enters a custom VEX builder context where the Redshift shaders and nodes can be networked together.
The redshift_vopnet node has a set of spare parameters to adjust the OpenGL settings to be used by this material in the Houdini viewports. This settings can be linked to parameters inside the Redshift material nodes to make possible an approximate preview of the Redshift materials in the OpenGL viewports. The available OpenGL settings areDiffuse color, Emission color, Specular color, Specular roughness and Alpha. There is also a switch to enable/disable theOpenGL lighting for this material.
Output VOP Nodes
Inside the Redshift Network SHOP node you can find two output nodes depending on the purpose of the network: Build a Redshift material or configure a Redshift light shader. The result of the network must be connected to the input of the relevant output node.
The default output available in the Redshift Network SHOP nodes is the material output. It is used to link the Redshift material nodes and build the Redshift shading networks. This output node has several inputs to link nodes to be used as material, displacement, bump or environment. The Light shader, that can be used to build custom lights using textured parameters and so on. This output node only has one input, used to link the Redshift light shader nodes.
Shader VOP Nodes
Inside the Redshift Network SHOP node, there is a complete set of custom VOP nodes designed to support all the avaiable Redshift shaders. Only the shader nodes available inside the Redshift Network SHOP can be used with Redshift. All the other Houdini VOP nodes, not compatible with the renderer, are filtered out. The VOP shaders are stored in several groups: Environments, Light Shaders, Materials, Textures, Tools and Utilities.
The Redshift shader VOP nodes support the parameters promotion feature, with the same workflow used by the native Mantra nodes.
Working with tangents
Some shaders support anisotropy specular reflections. This shading effects are rendered using tangent vectors that are not computed by Houdini by default. The tangents can be computed adding the PolyFrame SOP node with the configuration that you can see below. The “tangentu” and “tangentv” attributes will be extracted by the plugin as an additional channel named “tangent”, that can be used in the shaders to enable the anisotropy shading effects.
The plugin also supports multiple tangent maps extracted from the pair points attributes “tangentu”/“tangentv”, “tangentu2”/“tangentv2”, “tangentu3”/“tangentv3”, etc. The tangent maps can be referenced in the shaders using the “tangent”, “tangent2”, “tangent3”, etc. names.
Referencing COP2 nodes
The Redshift texture sampler node can reference the raster data available in the COP nodes using the standard Houdini “op:” syntax workflow. The COP textures are rasterized, stored in the Redshift textures cache and referenced from this place in the texture sampler node.
Referencing HDA embedded textures
The Redshift texture sampler node can also reference HDA embedded textures using the “opdef:” syntax workflow. In this case, all the HDA embedded files are unpacked, stored in the Redshift textures cache and referenced from this place in the texture sampler node.
Material SHOP HDAs
The plugin includes some basic predefined material SHOP digital assets to add to the scene the common Redshift materials.
You can build custom SHOP HDAs without problems. The plugin detects the Redshift SHOP HDAs from their operator name or from the their render mask. You can use the “rs_” prefix in the operator name to define a RS SHOP HDA (for example “rs_myFooMaterial”), or you canadd the “Redshift” word in the HDA render mask parameter. For example, you can use “Redshift OGL” as render masks to use the HDA for Redshift and OpenGL viewports.
Houdini 16.0 VOP-Based Shaders
Houdini 16 has replaced the/shop material context and the SHOP nodes for a new VOP-based shader workflow. The new workflow is supported by the Redshift plugin allowing the direct rendering of the “Redshift Material” output node, all the Redshift material nodes and adding a new “RS Material Builder”VOP node.
You can drag the “Redshift Material” output VOP node onto an object in the 3D Scene View to assign it as a material to that object. This is incredibly useful for trying things out at the /mat level, and for visualizing the output of a shader network at intermediate stages when debugging. The Redshift Material output VOP has an additional parameter to set the Material ID, that will be used if this node is used outside of the RS Material Builder or the conventional SHOP containers.
You can also drag any Redshift material node with the “Material” flag enabled and use it directly as material to that object.
Building shader trees at the /matlevel is great for prototyping and trying things out. However, when you're going to use material seriously, it’s a good idea to put the material network inside a “RS Material Builder”node. This node has the same workflow available in the old Redshift SHOP vopnet node.
