installation, known as the Automatic Method, locate your Houdini Preference directory and add the hdRpr package that will point it to the current directory. When your hdrpr download is complete, unpack the zip folder and open the folder located inside. Double-click on the activateHoudiniPlugin executable. A window should appear saying that the plugin has been activated. Once complete, open Houdini to confirm that the installation was successful. 4
and LOPS or Lighting Operator nodes, which work to generate and modify Universal Scene Description (USD) based scenes. There are several workflows that allow you to use the RPR plugin, but in each workflow, the viewport must be set to the RPR perspective. 6
Houdini, Houdini's desktop interface is set to Build by default. Go to Build in your 3D viewport and select the Solaris desktop option. This will change Houdini's desktop to the stage network, as well as open the Scene Graph Tree and Scene Graph Details panes. In your 3D viewport's perspective menu, find and select the RPR option to make it the active renderer. BUILD > SOLARIS 7
to utilize RPR's features is to simply switch from the object network to the stage network from the Network View pane. Once again, setting the active renderer to RPR in the perspective viewport. NETWORK VIEW > Other Networks > Stage 8
any issues with your viewport, you can always select Restart Render in the perspective menu to reset the stage. Houdini GL Perspective RPR Perspective 9
can also create a LOP Network node inside your Object Network if you aren't working entirely in RPR to create your scene. Add the node and double click to enter the network. Obj > TAB > LOP Network 10
imported SOP data has subgroups to separate the primitives for material assignment in the Object Network, be sure to activate the Subset Groups option in the Import Data sub menu and list the geometry's group names with a space in-between each. The SOP import node imports geometry from the Object network into a stage or LOP network. find SOP Path and open the Operator chooser and select the geometry you want. SOP IMPORT > SOP Path >/obj/... SOP IMPORT > Import Data > Subset Groups 12
import node is similar, but can also import cameras and lights from the Object network into the stage or LOP network. SCENE IMPORT > Objects > /obj/... To do the same for importing pre- existing cameras and lights from the Object network into the stage or LOP network, you can select the Scene Import (Cameras) or (Lights) nodes. 13
Merge node takes multiple inputs (in this case, one or more USD layers) and merges them into a stage containing one layer stack in the output. This is useful when you want to combine separate pieces of a scene graph, each authored by a different chain of LOP nodes, into a unified whole. 14
imports from external USD and USDA files or other LOP node chains into new Stage or LOP network as sublayers or instances that have already been made in other .hip files. You can import USD elements separately or import entire scenes using this layer. Sublayer SUBLAYER > Sublayer File > Desired File Path 15
Houdini test scenes (including the scene used in this tutorial) can be used for comprehension and experimentation using basic Houdini assets within a standard hdrpr workflow. These test scenes can be found here: Test Hdrpr Scenes https://drive.google.com/file/d/1JrIgvimsk4siq 615nmJcA4ZAb8uVzTCu/view?usp=sharing https://github.com/hshakula/hdRprDocs/tree/ master/asset/basicScene Test Scene (Sphere Plane) Test Scene (AMD Produced Basic Scene) 16
will apply renderer-specific geometry settings to geometry in the scene graph. Having multiple objects in a scene will require each of them to have this node if you wish for each of them to have separate Object IDs. Setting the ID option in the RPR Submenu will change the color of the designated geometry randomly for easy viewing. Render Geometry Settings PRIMITIVES > Desired object path ID > Desired Object ID Number 18
The Material Library node translates shader VOP or Vector Operator nodes into USD material primitives. The RPR Uber Shader is a multi-purpose shader intended for creating a wide range of real- world materials. It consolidates a number of components, or layers, that group certain properties of physical materials. The RPR Toon Shader is a shader intended for the mimicry of cel-shaded color with sharp shadow tones and highlights. The USD UV Texture material can also be applied to the color for mutliple materials. 20
• Color Parameter for base RGB color • Weight Value for diffuse weight • Roughness Value for diffuse roughness • Normal Parameters for setting diffuse normal The RPR Uber Shader is a multi-purpose shader and allows for reflective, refractive, transparent, emissive and subsurface properties. The diffuse is the default. 21
• Shadow Color Parameter for Shadow base color • Mid Level Mid Level Mix Value between Mid and Shadow base color • Mid Color Parameter for Mid base color • HIghlight Level/ Highlight Level Mix Value between Mid and Highlight base color • HIghlight Color Parameter for highlight base color • Interpolation Mode • Roughness Value for Roughness parameter The RPR Toon Shader does not allow for special properties at this time. 22
Material node will allow you to take the Materials you've setup in the Material Library and apply their properties to your primitives. PRIMITIVES > Desired object path MATERIAL PATH > Desired material path 24
/rubbertoy1/ Similar to the Assign Material node, the Material Linker node allows you to assign materials to designated geometry using rules you setup in the node itself. If the Material Linker is active, the assignment should appear automatically in the viewport. MATERIALS > Drag Desired Material > Desired geometry path 25
Toon Shader Update As of Hdrpr version 2.0.46, The RPR Toon Shader has been updated to include base RGB Color control parameter. The RPR Material Library is a prebuilt directory with preset materials that can be downloaded from the Radeon ProRender documentation website. The Import Material function located in the RPR dropdown menu will open a new window will appear revealing the library preset list, complete with images showing each material's characteristics. 26
material path The RPR Material Properties node will apply renderer-specific material ID settings to the designated Material path. Having multiple materials in a scene will require each of them to have this node if you wish for each of them to have separate Material IDs with separate numbers. Setting the ID option will change the color of the designated material randomly for easy viewing. ID > Desired Material ID Number 28
Render Variables in Houdini are referring to Arbitrary Output Variables, or AOVs. AOVs can be extremely useful for examining various aspects of a scene and can aid post-production processes. To use these, add the RPR Standard Render Vars node. You will see a checklist in your parameters pane that includes multiple AOV modes. Below is a demonstration to what each AOV may look like in the viewport. Beauty Albedo 30
Houdini do not currently support Cryptomatte. RPR2 does not currently support Ambient Occlusion. Full (Legacy) or RPR1 is necessary for this variable to be visible in the viewport. Heterogeneous Volume and volumetrics are also not currently visible in viewports with Full set as the viewport renderer. Depth passes are not visible in viewport until render. Level adjustment is potentially necessary. RPR Toon shader is not visible in RPR1 viewport or render. Full (RPR 2) and Full (Legacy) 34
X O Ambient Occlusion O X Beauty O O Albedo O O Depth O O Shading Normal O O Camera Normal O O Texture Coordinate O O Direct Illumination O O Indirect Illumination O O Direct Diffuse O O Indirect Diffuse O O Direct Reflect O O Indirect Reflect O O AOVs RPR1 RPR2 Refract O O Volume X X Emission O O Background O O Shadow Catcher O O Reflection Catcher O O Geometric Normal O O View Space Shading Normal X X Variance (Adaptive Sampling) O O Opacity O O World Coordinate O O Primitive ID O O Material ID O O AOVs RPR1 RPR2 Primitive ID Mask O O Material ID Mask O O Velocity O O 35
workflows may vary, achieving a Motion Blur effect in RPR for Houdini is possible using any node capable of changing a primitive's transform. One example of a typical workflow that allows for this is the Xform or Createxform node. This node belongs to a class of nodes that create or edit USD prims directly. This node operates in Create mode or Edit mode. Xform Transform Another example of a typical workflow to achieve a Motion Blur effect is using the Transform node. This node edit the transforms of USD primitives. 36
Set the desired start frame using the Set Keyframe option or the Keyframe button in the timeline. Set your desired Translate parameter. Set the desired end frame by scrubbing the timeline or setting the Global Animation End Frame. Set your desired Translate parameter. CREATEXFORM > Translate > (x,y,z) PRIMITIVE PATH > Desired geometry After adding the Xform node, set the Primitive path to the desired geometry. 37
Set the desired start frame using the Set Keyframe option or the Keyframe button in the timeline. Set your desired Translate parameter. Set the desired end frame by scrubbing the timeline or setting the Global Animation End Frame. Set your desired Translate parameter. TRANSFORM > Translate > (x,y,z) PRIMITIVES > Desired geometry/collection Similar to the Createxform node process, after adding the Transform node, set the Primitive path to the desired geometry. 38
Vars node, you'll need to add the Render Product node. The Render Product node sets your variables, your camera and your output resolution. First, set your Ordered Render Vars parameter by establishing the Render Variables that correspond to the AOVs you checked off in your Render Vars node. ORDERED RENDER VARS> /Render/Products/Vars/* 40
ProRender looks at when it exports its file to be rendered using Render Pool or your renderer of choice. It allows you to set the Render Quality and Render Mode that will be displayed in the final export. In the Standard Submenu, set your camera and your output resolution. RENDER SETTINGS > RPR Submenu 41
of samples to render for each pixel Max Ray Depth Value of maximum Ray Depth in viewport Diffuse Ray Depth Value of maximum number of time a light ray can be bounced off diffuse surfaces Glossy Ray Depth Value of the maximum number of ray bounces from specular surfaces By default, some settings are greyed out and set to Do Nothing. To change a setting, set it to Set or Create. 42
maximum number of times that a light ray can be refracted by clear transparent materials, such as glass Glossy Refraction Ray Depth Value of the maximum number of times that a light ray can be refracted by matte refractive materials, such as semi-frosted glass Shadow Ray Depth Value of accuracy of shadows cast by transparent objects 43
used to move light rays away from the geometry in your scene. Used for ray- surface intersection calculations Clamp Fireflies Radiance clamping to prevent noise Radiance Value of the maximum brightness of samples in your scene Interactive Resolution Downscale Controls how much rendering resolution is downscaled in the viewport 44
mode in the viewport, Go to the Render Mode in the RPR Submenu and switch from Global Illumination to Contour. RPR > Render Mode > Contour Contour OFF Contour ON 46
activated, a ToonTrace (Contour Settings) submenu will appear underneath the Render Mode. Here is where you will be able to turn on Antialiasing, and change the Linewidth, Normal Threshold, Primitive ID and Material ID Linewidth. Adjustment Examples 47
necessary to complete the node tree. First, enter a valid Export Path for the .rpr output file in your directory of your choice. Be sure to add the .rpr suffix to the end of your output filename. Set your Render Settings to your render settings path. If you're animating a camera, or running a simulation, be sure to set the Valid Frame Range to Render Specific Frame Range. EXPORT PATH > Desired file name.rpr If your exporting an animation, be sure to include .$F4 after your file name and before the .rpr output format. RENDER TO DISK > Begin RPR Export 49
specified in your Windows Explorer, and you should see your completed exported files. You should have and .RPR file, and .JSON file and several .RPRSB files located in the desired export folder. RPR files are the geometry data per frame. RPRSB files refer to texture, geometry, and material cache files. .JSON files record all other information, including your designated Render Variables. 50
USD Render ROP node writes the USD generated by a LOP network to a temp file, then launches an external process (by default, HUSK) to render an image or image sequence from the USD. Similar to RPR Export, if you're animating a camera, or running a simulation, be sure to set the Valid Frame Range to Render Specific Frame Range. USD Render ROP Renderer > RPR Set the desired Renderer to RPR before selecting your Render Settings. 51
path. The Render command is automatically set to husk. There is no need to change this. USD Render ROP If your exporting an animation, be sure to include .$F4 after your file name and before the output format. OVERRIDE OUTPUT IMAGE > Desired file name. * (.png, .exr,…) 52
your beauty AOV as a single file or a sequence of files if you've set your animation output correctly. Rendering to MPlay allows you to view your image or sequence once rendering is complete in the MPlay Viewer, a separate render viewing window. You can also switch between the designated Render Variables or AOVs and save them individually. USD Render ROP When you are ready, you can select Render to Disk or Render to MPlay. MPlay Viewer 53
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