intel Get Started with oneAPI Rendering Toolkit for Windows User Guide

: June 9, 2024
: Intel

Table of Contents

Configure Your System
Run Pre-Compiled Sample Applications
Troubleshooting
Notices and Disclaimers
References
Read User Manual Online (PDF format)
Download This Manual (PDF format)

Get Started with one API Rendering Toolkit for Windows
User Guide

The following instructions assume you have installed the Intel® one API Rendering Toolkit (Render Kit). If you do not have the toolkit installed, see Intel® one API Toolkits Installation Guides for installation options. Follow These Steps to Get Started with Intel® one API Rendering Toolkit

Configure your system.
Build and run sample applications.
Run the pre-compiled sample applications.
Next steps: Review additional resources to learn more about the Render Kit.

Configure Your System

To use the Intel ® one API Rendering Toolkit (Render Kit) samples, you first need to set up your system as follows:

Install the one API sample browser to access sample sources.
Install Microsoft Visual Studio with Cake and Windows* SDK to build the samples.
Install imaging tools.
Optional: Install GPU drivers.

Install the one API Sample Browser
You can access sample applications from the one API sample browser. The browser is distributed as part of the Intel® one API Base Toolkit (Base Kit) in the dev-utilities directory.
Install the Base Kit with Intel® one API Threading Building Blocks, which is available in both Render Kit and Base Kit. No other Base Kit components are required. See Base Kit product page for more information and download links.
NOTE You can also get the samples manually using Git*.
Install Microsoft Visual Studio with Cake and Windows* SDK*
Although Intel® neap Toolkits do not require Cake and Windows SDK , many one API samples are delivered as Make projects. To build such samples, you need to install Cake and Windows SDK.
To do this, install the Microsoft Visual Studio C++ development tools, which include Make tools in the desktop development with C++ workload. See Cake projects in Visual Studio for installation instructions.
Typically, the required components are installed from the optional section of the Visual Studio installer. Visual C++ Tools for Cake is installed by default as part of the Desktop Development with C++ workload. For more information about Cake, refer to CMake.org. For more information on the Windows SDK refer to
the Microsoft Dev Center Windows SDK.
Install Imaging Tools*
Render Kit samples and applications often require preprocessed images as input or generate images as output. To display and convert input and output images, you need to get imaging tools for staging Net PBM filetypes (PPM and PFM). Recommended tool is Image Magics. See the Image Magick website for standalone and package manager install instructions.
For GPU Users, Download and Install GPU Drivers

To download the driver, go to Graphics Drivers.
Click on the latest version of Intel® Graphics – Windows ® 10 DCH Drivers.
Run the installer.

Next Steps
Get started with the Intel ® one API Rendering Toolkit by building and running sample applications.
Feedback
Share your feedback on this article in the Intel ® one API Rendering Toolkit forum.
*Build and Run Sample Projects Using the Visual Studio Command Line
Prerequisite:** Configure your system.
To build and run a sample:

Locate a sample project using the Code Sample Browser for Intel® oneAPI Toolkits.
Build and run a sample project using CMake*.

Download Samples using the Code Sample Browser for Intel® one API Toolkits
Use the Code Sample Browser for Intel one API Toolkits to browse the collection of online Intel® one API samples. You can copy the samples to your local disk as buildable sample projects. Most Intel one API sample projects are built using Make* or Cake, so the build instructions are included as part of the sample in a README file. Code Sample Browser for Intel one API Toolkits is a stand-alone single-file executable that has no dependencies on dynamic runtime libraries.
For a list of components that support Cake, see Use Cake with one API Applications.
Important
An internet connection is required to download the samples for Intel one API Toolkits. For information on how to use this toolkit offline, see Developing in Offline Systems.
Code Sample Browser for Intel one API Toolkits does not work with system proxy settings and does not support WPAD proxy. If you have trouble connecting from behind a proxy, see Troubleshooting.
To download the Intel ® one API Rendering Toolkit (Render Kit) samples:

Open an x64 Native Tools Command Prompt for VS 2019 command window.
Set up environment variables:
call “C:\Program Files (x86)\Intel\one API\setvars.bat”
NOTE If you installed the Render Kit to a custom location, make sure to replace C:\Program Files (x86)\Intel\one API\ with the custom installation path before running the command.
From the terminal, run the Code Sample Browser for Intel one API Toolkits with C++ and C samples. neap-cli -l coppice
The one API CLI menu appears:
Select Create a project using arrow keys, then press Enter.
The language selection will appear.
Select the language for your sample. For your first project, select cup, then press Enter.
The toolkit samples list appears. Render Kit samples are located underneath the one API Libraries subtree.
Navigate to one API Libraries > Getting Started with Intel one API Rendering Toolkit > Intel Spray sample > 01_ospray_gsg, then press Enter.
Specify a location to download the project to. By default, it is the path from where you ran the Code Sample Browser for Intel one API Toolkits and project name.
Press Tab to select Create, then press Enter.
Repeat the steps to download samples for other components: 02_embree_gsg for Intel® Embraer, 03_openvkl_gsg for Intel® Open Volume Kernel Library, 04_oidn_gsg for Intel® Open Image
Denoise, and 05_ispc_gsg for Intel® Implicit SPMD Program Compiler (Intel® ISPC). The samples are numbered and staged to be tried in order.
Intel Open Volume Kernel Library 03_openvkl_gsg sample is available in the C language menu option of the Code Sample Browser for Intel one API Toolkits:
a. Select c language: b. Select the Intel Open VKL sample:

See Exploring Intel one API Samples from the Command Line for a video tutorial on creating a project with the command line.
Build and Run an Intel® Spray Sample using Cake*

Navigate to the folder where you downloaded the 01_ospray_gsg sample.
Run the following commands to build the sample:
midair build cd build cake .. cake –build . –config Release
Navigate to the Release directory.
Run the application.
.\ospTutorialCpp.exe
Review the output images with an image viewer application for PPM file type. For example, with Image Magick*:
\imdisplay.exe first Frame Cup. ppm \imdisplay.exe accumulated Frame Capp. ppm You should see the output images: • Single-accumulation render first Frame Cpp: • Ten-accumulation render accumulated Frame Cup:

**Build and Run an Intel® Embrey Sample using Cake***

Navigate to the folder where you downloaded the 02_embree_gsg sample.
Run the following commands to build the sample:
mkdir build
cd build
cake ..
cmake –build . –config Release
Navigate to the Release directory.
Run the application.

.\minimal.exe
The sample application performs two ray-to-triangle intersect tests with the Intel Embrey API. One test is successful, while the other test is a miss. Output is written to the terminal:
0.000000, 0.000000, -1.000000: Found intersection on geometry 0, primitive 0 at tsar=1.000000 1.000000, 1.000000, -1.000000: Did not find any intersection.
**Build and Run an Intel® Open Volume Kernel Library Sample using CMake***

Navigate to the folder where you downloaded the03_openvkl_gsg sample.
Run the following commands to build the sample:
midair build
cd build
cake ..
cake –build . –config Release
Navigate to the Release directory.
Run the application.

.\vklTutorial.exe
The sample application shows sampling within a procedurally generated volume and outputs. sampling,
gradient computation, and multi-attribute sampling. Output is written to the terminal.

**Build and Run an Intel® Open Image Denoise Sample using CMake***

Navigate to the folder where you downloaded the 04_oidn_gsg sample.
Run the following commands to build the sample:
midair build cd build cake ..
cake –build . –config Release
Navigate to the Release directory.
Convert the accumulated Frame Cup. ppm image to PFM format with LSB data ordering. For example, with the Image Magics* convert tool:
\magick.exe convert \01_ospray_gsg\build\Release \accumulated Frame Cup. ppm -endian LSB PFM: accumulated Frame Capp. p.m.
Run the application to denoise the image.
.\oidnDenoise.exe -her accumulated Frame Capp. p.m. -o denoised.pfm
Review the output image with an image viewer application for PPM file type. For example, with Image Magics*:
\imdisplay.exe denoised. p.m. • Original ten-accumulation render accumulated Frame Cup:

• Denoised result denoised. p.m.: Build and Run an Intel® Implicit SPMD Program Compiler Sample using CMake*

Navigate to the folder where you downloaded the 05_ispc_gsg sample.
Run the following commands to build the sample:
midair build
cd build
cake ..
cake –build .
Run a single-target sample application:
.\simple.exe
Run a multi-target sample application:
./simple_multi.exe
The application executes a simple floating-point array operation. The result is printed to the stout.

0: simple(0.000000) = 0.000000	8: simple(8.000000) = 2.828427
1: simple(1.000000) = 1.000000	9: simple(9.000000) = 3.000000
2: simple(2.000000) = 4.000000	10: simple(10.000000) = 3.162278
3: simple(3.000000) = 1.732051	11: simple(11.000000) = 3.316625
4: simple(4.000000) = 2.000000	12: simple(12.000000) = 3.464102
5: simple(5.000000) = 2.236068	13: simple(13.000000) = 3.605551
6: simple(6.000000) = 2.449490	14: simple(14.000000) = 3.741657
7: simple(7.000000) = 2.645751	15: simple(15.000000) = 3.872983

Next Steps
Explore additional resources in Next Steps.

Run Pre-Compiled Sample Applications

In addition to libraries, the Intel® onlap Rendering Toolkit provides pre- compiled sample applications to
highlight toolkit features. These pre-compiled applications often use external graphics libraries to show
features in an interactive mode. In this section, learn to run the pre- compiled interactive applications.

Run Pre-compiled Interactive Applications

Run a pre-compiled sop Examples application with Intel ® Spray.
sop Examples demonstrates basic rendering of an interactive scene with Intel Spray. It has GUI controls that you can toggle to explore Intel Spray features.
Run a pre-compiled triangle geometry application with Intel ® Embrey. triangle geometry, as other Intel Embrey samples, demonstrates core ray-tracing compute capability.
Use the triangle geometry to explore Intel Embrey features.
Run a pre-compiled vole Examples application with Intel ® Open Volume Kernel Library (Intel® Open VKL). vole Examples demonstrates basic rendering of an interactive scene with Intel Open VKL. It has GUI controls typical for volume rendering visualization.

NOTE Intel ® Open Image Denoise is used as a postprocessing feature in ospExamples sample application and in Intel Spray Studio. Intel Open Image Denoise does not have a standalone interactive application’s
Run Intel® OSPRay Studio Showcase Application
Intel Spray Studio combines Render Kit libraries into a state-of-art showcase application. Try the precompiled Intel Spray Studio application before exploring the source code to use it for your own projects.
Intel Spray Studio features:

A reference scene graph for loading, storing, and transforming scene geometry, textures, and parameters in an interactive environment
GUI-based scene instrumentation for rendering parameter control of an interactive application
C++ plugin infrastructure for custom controls
Input/output: Wave front OBJ, GLTF, HDR textures with Open Image IO, static image output
Intel Open Image Denoise post-processing passes with the osprey module denoiser library from Intel Spray
Python* bindings to script rendering
Camera animation controls
Multi-node rendering with MPI

Run a Sample with Intel® OSPRay
This walkthrough demonstrates how to run an interactive sample application with Intel® OSPRay from the Intel® oneAPI Rendering Toolkit (Render Kit) for Windows* OS.
Prerequisite: Configure your system.
To run the application:

Open a command prompt.
Set up environment variables:
call “C:\Program Files (x86)\Intel\oneAPI\setvars.bat”
NOTE If you installed the Render Kit to a custom location, make sure to replace C:\Program Files (x86)\Intel\oneAPI\ with the custom installation path before running the command.
Go to a writable directory and create a directory to store supporting files. For example, create the rkgsg folder : cd %USERPROFILE% midair rkgsg cdrkgsg
Run ospExamples: ospExamples.exe

A new GUI window will open with multiple simple scenes composed of basic geometry types, lights, and volumes. You can edit the scene by clicking the drop-down button’s Controls and Tips
You can control the scene view with a mouse as follows:

Right-click to move the camera in and out from the look-at point.
Left-click to rotate.
Use a mouse wheel to pan.
This also reports the geometry ID for intersected geometry under the cursor in a terminal.
Drag and drop to move the camera.

You can also use the following keyboard controls:

Press G to show/hide the user interface.
Press Q to quit the application.
You can also control the scene from the control pane:
Try different geometric and volumetric scenes. View them under different renderers.
Cancel frame on interaction allows for more continuous animation during navigation.
Enable showing depth to show relative depth at the ray intersection with the scene from each pixel location of the camera.
Enable showing albedo to show the albedo of the material at the ray intersection with the scene from each pixel location of the camera.
Enable denoiser to denoise each frame with Intel® Open Image Denoised
Note: The denoiser might work be better observed with some geometries than with others. For example, the Streamlines predefined scene set shows convergence with denoise more clearly.

NOTE If osprey module denoiser is not available in your distribution, you can get it using the Superbill as described in Next Steps.

Change pixel filter to review the different anti-aliasing methods available in the API.
Change pixel samples, which is the number of scene samples per pixel in one accumulation. Higher samples results in longer rendering times, but faster convergence per accumulation. Less samples per pixel results faster application performance.
Change maximum path length parameter, which is the number of path reflections or refractions per sample. A higher number is more accurate, while a lower number is faster to compute.
Change roulette path length, which is the threshold or reflections or refractions at which to randomly end the traversal of a ray. A higher number is more accurate, while a lower number is faster to compute.
Change sample contributions. Sample contribution less than the min Contribution will not affect the scene. A lower number is more accurate, while a higher number is faster to compute.
Change camera motion blur to control the blur affect while moving the camera. A value of 0 turns the blur off.
Enable Render Sun Sky to turn on a controllable scene horizon. The scene will reflect the horizon as configured from GUI pop-up parameters.

Next Steps

Run pre-compiled sample applications for other Render Kit components.
Explore additional resources in Next Steps.

Run Intel® Embree Sample
This tutorial shows how to run an interactive Intel® Embrey pre-compiled sample applications included in the Intel® one API Rendering Toolkit (Render Kit). This sample demonstrates how to generate an image with basic geometry using Intel Embrey.
The triangle geometry sample application shown in the tutorial uses a graphical user interface to create a static cube and ground plane using triangle vertices.
Prerequisite: Configure your system.
To run the application:

Open a command prompt.
Set up environment variables:
call “C:\Program Files (x86)\Intel\one API\setvars.bat”
NOTE If you installed the Render Kit to a custom location, make sure to replace C:\Program Files (x86)\Intel\one API\ with the custom installation path before running the command.
Go to a writable directory and create a directory to store supporting files. For example, create the rk_gsg folder :
cd %USERPROFILE%
midair rigs
cd rigs
Run the triangle geometry sample: triangle_geometry.exe
A new window opens with a 3D ray-traced cube. To move camera, click and drag the left mouse button or use W, A, S, D or arrow keys. For details about the sample, see Chapter 9 in the Intel Embrey documentation.

Tips and Observations

To move camera, click and drag the left mouse button or use W, A, S, D buttons or arrow keys.
This sample demonstrates how to generate an image with basic geometry using Intel Embrey.
triangle geometry sample features:
A hard-coded array of simple float vertex data, consisting of location of the corners of the cube and the ground plane.
The definition of index lists to construct triangles from the vertices.
API-defined geometry data structures to create and commit vertex and index data into the scene.
A multi-threaded compute hierarchy for ray-tracing over the image frame.
Computing rays is divided into tiles of screen pixels. Tiles are split amongst threads.
Each tile performs ray intersect tests for each pixel in the tile.
In addition to basic ray intersect tests that determine the triangle colors, a shadow intersect (occlusion) test is performed at the intersection point for one hard-coded fixed light direction.
Final pixels have color data computed from the rays packed into RGB color triplets.
Scaffolding abstraction provides much of the glue code. This abstraction is used heavily in other Intel
Embrey sample applications. The samples abstraction includes:
Setup for call backs to initialization, rendering, and tear-down functions
Data structures for managing scene data
Keyboard and mouse input/output
API hooks into operating system window management code for visualization

See the application source in triangle_geometry_device.cpp in the Intel Embraer GitHub* repository.
Intel Embrey relationship with other Render Kit components

Intel® Spray, the open scalable portable ray-tracing engine, uses Intel Embrey to generate images. Intel Spray also provisions objects and functionality typical to 3D scenes.
Intel Spray provisions include volume and geometry objects, materials, textures, lights, camera, frame buffers, MPI-based distributed computing, and others.
For developers with OpenGL*-like background, Intel Spray may be a better way to start exploration of the toolkit than the Intel Embrey.
Intel Embrey path tracer example program provides a minimal and logical introduction to a path tracer. Access a full professional visualization implementation of a path tracer renderer within the Intel Spray API.
Intel Embrey capability is centered around geometric ray-tracing. In contrast, Intel® Open Volume Kernel Library (Intel® Open VKL) provides volume visualization and sampling capability.
Images rendered with the Intel Embrey can be denoised with Intel® Open Image Denoise. However, Intel Spray provisions extended frame buffer channel access to simplify managing data denoising. The result is denoised high-quality images at a reduced ray tracing compute cost.

Next Steps

Run pre-compiled sample applications for other Render Kit components.
See Next Steps for more resources.

Run Intel® Open Volume Kernel Library (Intel® Open VKL) Sample
This tutorial describes how to run a pre-compiled interactive sample application built on Intel® Open
Volume Kernel Library (Intel® Open VKL).
The vole Examples sample application renders the Intel Open VKL API results to screen through a graphical interface.
Prerequisite: Configure your system.
To run the application:

Open a command prompt.
Set up environment variables:
call “C:\Program Files (x86)\Intel\one API\setvars.bat”
NOTE If you installed the Render Kit to a custom location, make sure to replace C:\Program Files (x86)\Intel\one API\ with the custom installation path before running the command.
Go to a writable directory and create a directory to store supporting files. For example, create the
rags folder :
cd %USERPROFILE%
midair rigs
cd rigs
Run the sample application:
vole Examples.exe
The sample results will open in a new GUI window.

The following controls are available:

Left-click (Mouse1) and drag to rotate camera.
Right-click (Mouse2) and drag to zoom camera.
Middle-click (Mouse3) and drag to pan camera.
Select different transfer functions, Intel Open VKL API values, and rendering controls to visualize the volume.

NOTE User interface elements may overlap. Drag and drop the blue control bar to see all controls.
Tips and Observations

Different renderer modes are available from the rendering drop-down. These modes correspond to contemporary volume sampling and rendering applications.
Density Path Tracer renderer demonstrates path tracing within a volume. It uses vole Compute Sample() in support of a Woodcock-tracking sampling algorithm. Use the dialog boxes to control algorithm parameters. See DensityPathTracer.cpp.
Hit-iterator renderer demonstrates hit-iterator and gradient computation functionality. It uses vole Iterate it() and vole Compute Gradient(). This example also demonstrates shadow testing. See HitIteratorRenderer.cpp.
Ray-march iterator demonstrates interval iteration and computation of a volume sample. It uses vole Iterate Interval() and vole Compute Sample(). See RayMarchIteratorRenderer.cpp.
When exploring the samples, note that the code is aliased and modular to support the interactive rendering window. To better understand the code, start with the render Pixel() function.
ISPC modes correspond with code implementations built on the Intel® Implicit SPMD Program Compiler. These implementations take advantage of SIMD capabilities of modern processors and provide more opportunity for performance.

Next Steps

Run pre-compiled sample applications for other Render Kit components.
See Next Steps for more resources.

Run Intel® Spray Studio
This walkthrough demonstrates how to run the Intel® Spray Studio application. Intel Spray Studio is a showcase application included in the Intel® neap Rendering Toolkit (Render Kit). It is an interactive and extendable ray- tracing application.
Prerequisite: Configure your system.
To run the application:

Open a command prompt.
Set up environment variables:
call “C:\Program Files (x86)\Intel\one API\setvars.bat”
NOTE If you installed the Render Kit to a custom location, make sure to replace C:\Program Files
(x86)\Intel\one API\ with the custom installation path before running the command.
Go to a writable directory and create a directory to store supporting and result files. For example,
create the rigs folder :
cd %USERPROFILE% midair rigs cd rigs
Run Intel Spray Studio: ospStudio.exe
You should see an interactive rendering window:
In the rendering window, go to File > Demo Scene and select one of the predefined demo scenes. NOTE Some scenes demonstrate Intel® Open Volume Kernel Library integration capability.
Review the selected scene. For example, the Multilevel Hierarchy demo looks as follows: You can control the scene view with a mouse as follows:
• Right-click to move the camera in and out from the look-at point.
• Left-click to rotate.
• Scroll the mouse wheel to zoom in and out.
• Drag and drop to move the camera.
You can also use the following keyboard controls:
• UP/DOWN: Move the camera along the Z axis (in and out).
• ALT+UP/ALT+DOWN: Move the camera along the Y axis (up or down).
• LEFT: Move the camera to the left along the X axis.
• RIGHT: Move the camera to the right along the X axis.
• W/S: Change camera elevation.
• ALT+S: Save a frame as a file to a local directory.
• A/D: Change camera azimuth.
• ALT+A/ALT+D: Change camera roll.
• G: Show/Hide the user interface.
• Q: Quit the application.
• P: Print a scene graph to the shell.
• M: Print a material registry to the shell.
• B: Print frame bounds.
• V: Print camera parameters to the shell.
• =: Push a location to save camera parameters.
• -: Pop a location to save camera parameters.
• 0-9: Set a camera snapshot.
• Hold X, hold Y, hold Z: Keep axis constrained for camera movement.
You can save output image from Menu > Save… > Screenshot in a preferred image format. The image is saved to the working rags directory as studio..
You can review the saved screenshot with your preferred image viewer.

Next Steps

Run pre-compiled sample applications for other Render Kit components.
See Next Steps for more resources.

Next Steps
Explore additional Intel ® one API Rendering Toolkit (Render Kit) resources.
API Manuals
Render Kit libraries provide C99-based API interfaces. API manuals are located on component library public webpages.

Intel® OSPRay API manual
Intel® Embree API manual
Intel® Open Volume Kernel Library (Intel® Open VKL) API manual
Intel® Open Image Denoise API manual

All C99 API headers compile under C++11. If you prefer C++, some Render Kit libraries expose C++ API wrappers functionality defined in header files.

Library	Header
Intel Spray	ospray_cpp.h
Intel Open Image Denoise	oidn.hpp

Advanced Sample Program Sources
For each component sample, source is available in the component GitHub* repository:

Intel Spray sample sources
Intel Embrey sample sources
For sample description, see chapter 9 in Intel Embrey guide.
Intel Open VKL sample sources
Intel Open Image Denoise sample sources
This is command line only.
Intel Spray Studio source

Superbills

You can deploy a local environment to build and run all samples with the superbill. The superbill is a complete automated Cake* script to get and build all Render Kit libraries and samples. The superbill is a recommended method for:

Exploring all samples in an easy and comprehensive sandbox. Editing and rebuilding them quickly.
Getting many prerequisites for building the libraries automatically
Reviewing internal library source code
Modifying Render Kit functionality, including staging library build time optional features
The superbill script is delivered as the ruttily component of the Render Kit distribution. It is also located in the Render Kit GitHub portal. For a superbill script walkthrough, see the document for your operating system:
Build Intel one API Rendering Toolkit Libraries for Windows* OS
Build Intel one API Rendering Toolkit Libraries for Linux* OS
Build Intel one API Rendering Toolkit Libraries for macOS*

Forums and Feedback
Ask questions and provide feedback on the Intel oneAPI Rendering Toolkit forum.
Report technical issues directly on component GitHub repositories:

Intel Spray repository
Intel Embrey repository
Intel Open VKL repository
Intel Open Image Denoise repository
Intel Spray Studio repository

Troubleshooting

This section describes known problems you may encounter when using the Intel® one API Rendering Toolkit (Render Kit).
For technical support, visit Intel ® one API Rendering Toolkit Community Forum.
Error: No protocol specified
You might see the following error when running a GUI-based application from a Docker* container:
No protocol specified
Error 65544: X11: Failed to open display :0
Terminate called after throwing an instance of ‘sty::runtime error ’
What(): Failed to initialize GLFW!
Aborted (core dumped)
Solution: Before launching the application, make sure you run the xhost command in the Docker container:
host +

Notices and Disclaimers

Intel technologies may require enabled hardware, software or service activation.
No product or component can be absolutely secure.
Your costs and results may vary.
© Intel Corporation. Intel, the Intel logo, and other Intel marks are trademarks of Intel Corporation or its subsidiaries. Other names and brands may be claimed as the property of others.
Product and Performance Information
Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.
Notice revision #20201201
No license (express or implied, by estoppel or otherwise) to any intellectual property rights is granted by this document.
The products described may contain design defects or errors known as errata which may cause the product to deviate from published specifications. Current characterized errata are available on request.
Intel disclaims all express and implied warranties, including without limitation, the implied warranties of merchantability, fitness for a particular purpose, and non-infringement, as well as any warranty arising from course of performance, course of dealing, or usage in trade.