Intro to Proxies

Intro to Proxies

Table Of Contents

Introduction

Redshift Proxies allow you to place previously exported Redshift Proxy Files (.rs) files in your scenes without actually loading the geometry until it is actually needed at render time. You can think of a Redshift Proxy as an actual Redshift scene all on its own, they can even contain other Redshift Proxies.

Using Redshift Proxies in your scene is a 2 step process. First you export a Redshift Proxy File, then you import and place a Redshift Proxy in your scene and associate it with the exported file.

Using proxies has several advantages over in-scene objects, namely:

Proxies are loaded by Redshift on demand and will therefore only use resources when they are needed (when a ray intersects the proxy's bounding box).
Proxies have almost no time cost during scene translation. Extracting large amounts of geometry can be slow and using proxies means you pay that cost only once, when you first export the Redshift Proxy File.
Proxies are stored in an optimized format on disk so that the renderer can immediately use the data after loading from disk without additional processing or memory overhead.
Support for object types including animated and deforming meshes, hair, strands, instances, volume containers, lights and any materials/shaders applied to these objects.

The main disadvantages of using proxies:

Making edits to the proxy can be more time consuming than if the original data is part of the scene (as it requires making changes in another file and re-exporting the Redshift Proxy File)
After export Redshift Proxy geometry cannot be deformed or otherwise modified aside from adjusting tessellation settings. For example, you cannot animate components inside a proxy after export, but you can animate the position, rotation and scale of the proxy as a whole rigid object.
Animated proxies can be heavyweight because they are per-frame caches.

Redshift Proxies provide the option to use either the materials embedded in the Redshift Proxy File, or to replace those materials with materials from the scene where the proxy is placed.

Redshift Proxy Files are DCC-independent, so for example you can export a Redshift Proxy File from Maya and import it as a proxy in Houdini, or vice-versa.

There are currently some important limitations in sharing Redshift Proxy Files between DCCs:

The embedded shaders in a Redshift Proxy File from one DCC may not be available in another DCC. For example a Redshift Proxy File containing a Softimage Lambert material will not render correctly when placed as a proxy in Maya.
Certain light types native to a particular DCC may cause errors when rendered in another DCC.

To avoid this issue, we recommend always using one of the From Scene material modes when sharing Redshift Proxy Files between DCCs until we resolve this limitation.

Important Considerations

When working with Redshift Proxies, it is helpful to keep the following things in mind:

You cannot retrieve the original Maya, 3ds Max or Softimage mesh from a Redshift Proxy File, so it is advisable to keep the original source data that was used to export the Redshift Proxy.
When placing multiple copies of a Redshift Proxy in a scene, it is much more efficient for memory and performance to create a single Redshift Proxy and then create multiple instances of this proxy and place them as desired.

The data exported with your Redshift Proxy is determined by your Render Settings at the time of export, by default Redshift will try to discard as much unnecessary data as possible to achieve the most efficient file size.

UVs, Vertex Color, & Other Per-Vertex Attributes

When exporting a set of objects as a Redshift Proxy File, only the vertex attributes used by the currently assigned shaders are included in the exported data. This is an important optimization to prevent file bloat. When a proxy file will be used as-is, without overriding materials, this is not an issue. However, when using proxy material overrides, this can cause unexpected behavior if the overriding material requires vertex data that was stripped at export time because it was unused. So if you need certain attributes for your proxies at any point down the line, make sure that a shader attached to your proxy object is making use of those attributes. For example, if you have a sphere with a spherical texture projection and an untextured simple material assigned, the texture projection will be stripped at proxy file export time because it is not used by the currently assigned material. If this proxy is then placed in another scene and the material is overridden by a material that does use UVs, it will render incorrectly due to the missing UVs.

Motion Blur

In order for Redshift Proxies to render with Motion Blur you must make sure that motion blur is enabled in your Render Settings at the time of export.

Motion blur can be disabled on proxies after export but individual motion blur settings like frame duration cannot be changed after the fact, you must re-export your proxy if you wish to change its motion blur settings.

Instancing & Tessellation

If you are planning on instancing your Redshift Proxies please keep in mind that you can only use fixed tessellation.

Adaptive tessellation cannot be used when instancing in Redshift.

Creating & Exporting Proxies

To export a proxy file go to the Render Properties tab, enable the "Scene as Proxy" option (1), and define the output path (2). Once enabled, the Render function (3) will save a Redshift proxy file instead of saving an image file. If an animation range has been specified, multiple proxy files are generated based on the file name and path provided.

Export Parameters

Redshift Proxy Export Options

Scene as Proxy

Enables the export function of Redshift Proxy Files when the "Render" button is pressed.

Output Folder

This path specifies the output location of the proxy file.

The name of the file is determined by the following elements in this order:

Name of the scene
Name of the Render Layer
User Prefix
Frame Padding
File extension: .rs

User Prefix

Specifies a prefix for the naming of proxy files.

Frame Padding

Specifies the frame padding to be used with a sequence of proxy files.

Export Connectivity Data

Enabling this option is only necessary if you need to apply tessellation & displacement to the proxy after you’ve placed it in a scene and the original mesh does not have tessellation or displacement applied. Enabling this option increases the size of the proxy file, so it should only be used if necessary.

Polygon Connectivity Data will be exported automatically for any objects that already make use of tessellation & displacement.

Enable Compression

This option enables file compression to reduce file size for exported Redshift Proxies. In some cases, the compression can reduce the file size by 50% or more.

In general compression leads to slower export and load times. However, if a bottleneck in your pipeline is slow data transfer performance — like slow storage drives or a slow network — then enabling file compression could lead to a performance improvement thanks to the smaller file sizes. If you have a fast network and fast storage like an SSD then performance might be slower due to the processing time needed to decompress the proxy files. These are the sorts of things to consider when determining whether to enable or disable compression.

Keep unused attr.

When disabled, Redshift discards as much unused and unnecessary data as possible to achieve the most efficient file size.

Export Camera

When enabled the active camera is exported to the proxy file.

If a proxy is used to render directly with Command Line Rendering the Image Settings used at the time of export are used for the rendered frames.

Using Proxies

Proxy Object Parameters

Redshift Proxy Mesh

Select proxy file

This field specifies the Redshift Proxy File. You can navigate to and select the proxy file by using the folder icon to the right of this field.

Force IPR Update

This button forces a refresh of the proxy when rendering in the IPR. This button avoids having to restart the IPR mode and a complete reprocessing of the scene.

Material Mode

These options control how materials are handled for this proxy and allows from materials within the proxy file to be overridden with materials defined in the current scene.

From Proxy: uses the materials and shaders assigned to objects when the proxy file was exported as-is.
All from one: overrides all material assignments in the proxy file with the scene material assigned to the placeholder mesh.
From Placeholder: allows individual materials in the proxy file to be overridden with scene materials by looking for matching names. See the section Overriding Proxies for additional details.

Proxy display

The "Reset proxy Bound-box size" button resets any scale transforms back to the original proxy size.

Exclude Proxy Items

This area controls which objects are loaded from the proxy, allowing you to show or hide objects. After loading a proxy, the Update List button refreshes the list for each object type.

Overrides

Override Mode

Controls how the behavior of the override checkboxes from the following options:

From file: All overrides come from the proxy file at the time of export.
From proxy: Overrides are enabled based on the overrides checkboxes and any attributes from the placeholder object.
Leave alone: No overrides occur.

These checkboxes control whether the corresponding attributes of the objects inside the proxy file should be overridden by the same attributes of the proxy placeholder object. For example, if you want to assign an Object ID of 5 to the contents of a proxy file, you would set the Object ID of the placeholder object to 5 and enable the Object ID override.

Object ID
Visibility & Matte
Tessellation & Displacement
Trace Sets
User Data

External Proxy References / How To Transfer Proxies

Given that Redshift proxies can contain anything in a Redshift scene, this means that they can externally reference image files (such as EXR, PNG, etc), volume grids (like OpenVDB) and even other proxy files!

These external file references are stored in Redshift proxies both as absolute paths and as relative paths. Let's look at that with an example.

Let's say that a proxy file proxy.rs is exported in folder C:\MyProxies and it contains a shader that references texture mytexture.png which is under C:\MyProxies\Textures

The folder structre would look like this

| - [MyProxies] | --- proxy.rs | --- [Textures] | ---- mytexture.png

Within the proxy.rs file, the reference to mytexture.png will be saved both as:

An absolute path filename, i.e C:\MyProxies\Textures\mytexture.png
A relative path, i.e .\Textures\mytexture.png

Redshift contains file paths both as absolute and relative in order to facilitate the "transporting" of proxy files and their external references.

To explain with an example: let's say that the above proxy and texture (and their folder structure) were to be copy/pasted on folder C:\MyOtherProxies and the original C:\MyProxies folder was deleted.

The absolute path would no longer work because there's no C:\MyProxies\Textures\mytexture.png file anymore! (we deleted the folder!)

But the relative path would still work! Because, relative to C:\MyOtherProxies\proxy.rs there would still be a .\Textures\mytexture.png path.

Now let's consider a proxy file that references a texture folder on a completely different drive! For example:

[C:] | - [MyProxies] | --- proxy.rs [D:] | - [Textures] | ---- mytexture.png

Unfortunately, in such a case it's no longer possible to construct a relative path because path C:\MyProxies\proxy.rs and path D:\Textures\mytexture.png have no common "root"

So, using this folder layout, if the textures were to be moved to a new drive (say, E:\), then the proxy would no longer be able to find them.

In such cases, we recommend using Redshift's path override environment variables

If your texture folder used to be D:\Textures and now it's E:\Textures, you can use the REDSHIFT_PATHOVERRIDE_FILE or REDSHIFT_PATHOVERRIDE_STRING to tell Redshift to turn E:\Textures.

The online documentation page explains how to do that with an example.

If you don't know what external references a proxy might contain, you can use redshiftCmdLine's -printdependencies switch (followed by the proxy's filename) to list these.