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Amber is a multi-API shader test framework.

Amber lets you capture and communicate shader bugs with the fluidity and ease of a scripting flow:

  • No graphics API programming is required.
    • Supports Vulkan graphics API
    • WIP: Supports Dawn graphics API
  • A single text string (or file) maps to a single graphics API pipeline test case. The text includes:
    • Input data, including buffers and images.
    • Shaders.
    • Expectations for the result of running the pipeline.
  • Shaders can be expressed in binary form (as hex), in SPIR-V assembly, or in a higher level shader language.
  • After executing the pipeline, result buffers and images can be saved to output files.

Amber is influenced by Talvos and VkRunner. The VkScript syntax matches the format used by VkRunner.

This is not an officially supported Google product.

Writing Amber Tests

Working with Amber involves writing input test files. Some example files can be see in the tests/cases folder.

The main input format is Amberscript. New features are added to AmberScript as Amber is enhanced. This is the preferred format in which new script files are written.

Clear test as AmberScript

SHADER vertex vtex_shader PASSTHROUGH
SHADER fragment frag_shader GLSL
#version 430

layout(location = 0) in vec4 color_in;
layout(location = 0) out vec4 color_out;

void main() {
  color_out = color_in;


PIPELINE graphics my_pipeline
  ATTACH vtex_shader
  ATTACH frag_shader

  BIND BUFFER img_buf AS color LOCATION 0

CLEAR my_pipeline
EXPECT img_buf IDX 0 0 SIZE 256 256 EQ_RGBA 0 0 0 0

The VkScript format is supported for historic reasons. It is based off, and very closely matches, the format accepted by VkRunner. There are no new features being added to VkScript, it is for historical use.

Clear test as VkScript


[vertex shader passthrough]

[fragment shader]
#version 430

layout(location = 0) in vec4 color_in;
layout(location = 0) out vec4 color_out;

void main() {
  color_out = color_in;

relative probe rect rgba (0.0, 0.0, 1.0, 1.0) (0, 0, 0, 0)


  • Recommended: Configure at least one backend. See Backends below.
  • Git
  • CMake (version 3.7+ enables automatic discovery of an installed Vulkan SDK)
  • Ninja (or other build tool)
  • Python, for fetching dependencies and building Vulkan wrappers


git clone
cd amber
mkdir -p out/Debug
cd out/Debug
cmake -GNinja ../..


  • On Windows, Amber normally statically links against the C runtime library. To override this and link against a shared C runtime, CMake option -DAMBER_ENABLE_SHARED_CRT. This will cause Amber to be built with /MD for release builds or /MDd for debug builds.


  • Android build needs Android SDK 28, Android NDK r25b, Java 8. If you prefer other versions of Android SDK, Android NDK, Java, then you can change ANDROID_PLATFORM and ANDROID_BUILD_TOOL_VERSION in tools/
  • Set up Android SDK path by running export ANDROID_SDK_HOME=path/to/Android/SDK in your shell.
  • Set up Android NDK path by running export ANDROID_NDK_HOME=path/to/Android/NDK in your shell.
  • Generate a KeyStore using keytool command and set up KEY_STORE_PATH env variable for the KeyStore file path.
  • Run ./tools/ [build output directory path].

Android plain executable

It is possible to obtain a plain executable for Android, as opposed to an APK, with the following:

git clone
cd amber

./tools/ . samples/ third_party/
./tools/ . .

mkdir build
cd build
mkdir app
mkdir libs
${ANDROID_NDK_HOME}/ndk-build -C ../samples NDK_PROJECT_PATH=. NDK_LIBS_OUT=`pwd`/libs NDK_APP_OUT=`pwd`/app

The list of target ABIs can be configured in samples/jni/ by editing the APP_ABI entry:

APP_ABI := arm64-v8a armeabi-v7a x86 x86_64

The resulting executable will be produced as build/app/local/<abi>/amber_ndk. This executable can be run via the adb shell on your device, e.g. under /data/local/tmp (/sdcard is generally not suitable because it is mounted with a non-executable flag). Also, vulkan layers may not be available to this executable as it is not an app, so make sure to use the -d flag to disable Vulkan layers:

adb push build/app/local/<abi>/amber_ndk /data/local/tmp
adb shell
# Now on device shell
cd /data/local/tmp
./amber_ndk -d <shader-test-files>

Optional components

The components which build up Amber can be enabled or disabled as needed. Any option with _SKIP_ in the name is on by default, any with _USE_ is off by default.

The available flags which can be defined are:

  • AMBER_SKIP_TESTS -- Skip building Amber unit tests
  • AMBER_SKIP_SAMPLES -- Skip building the Amber sample applications
  • AMBER_SKIP_SPIRV_TOOLS -- Disable the SPIRV-Tools integration
  • AMBER_SKIP_SHADERC -- Disable the ShaderC integration
  • AMBER_SKIP_LODEPNG -- Disable the LodePNG integration
  • AMBER_USE_DXC -- Enables DXC as a shader compiler
  • AMBER_USE_LOCAL_VULKAN -- Does not try to find the Vulkan SDK, builds needed components locally
  • AMBER_USE_CLSPV -- Enables CLSPV as a shader compiler
  • AMBER_USE_SWIFTSHADER -- Builds Swiftshader so it can be used as a Vulkan ICD


DXC can be enabled in Amber by adding the -DAMBER_USE_DXC=true flag when running cmake.

Build Bots

There are a number of build bots to verify Amber continues to compile and run on the various targets. Due to bot limitations, the integration tests are not being run on the bots, just the unit tests.


Amber is designed to run against different graphics APIs. Amber will build if no graphics API is found, but will only allow verifying the syntax of the amber script files.

Currently the Vulkan and Dawn graphics APIs are supported.

Using Vulkan as a backend

A Vulkan implementation is found by CMake in the following priority order:

  • If AMBER_USE_LOCAL_VULKAN is enable the headers, loader and layers will be built locally and not found on the system.

  • If an enclosing CMake project includes the Vulkan-Headers CMake project, then headers will be picked up from there.

    In this case the CMake variable Vulkan_LIBRARIES can name the Vulkan library, or a default of vulkan will be used.

  • If you have CMake 3.7 or later, then the Vulkan implementation will be found from a Vulkan SDK as published by LunarG.

    Environment variables:

    • VULKAN_SDK should point to the platform-specific SDK directory that contains the include and lib directories.
    • VK_ICD_FILENAMES should point to the ICD JSON file.
    • VK_LAYER_PATH should point to the explicit_layer.d folder.
    • LD_LIBRARY_PATH must contain the $VULKAN_SDK/lib/ folder for the validation libraries.
    export VULKAN_SDK=$HOME/vulkan-macos-
    export VK_ICD_FILENAMES=$VULKAN_SDK/etc/vulkan/icd.d/MoltenVK_icd.json
    export VK_LAYER_PATH=$VULKAN_SDK/etc/vulkan/explicit_layer.d

Using Dawn as a backend

We assume you have built Dawn from source, and have access to both the source and build trees. To build a Dawn backend for Amber, set the following CMake variables when configuring Amber:

  • Dawn_INCLUDE_DIR: The directory containing dawn/dawn_export.h (in the source tree).
  • Dawn_GEN_INCLUDE_DIR: The directory containing generated header dawn/dawncpp.h (in the build output tree).
  • Dawn_LIBRARY_DIR: The directory containing the dawn_native library (in the build output tree).

Using SwiftShader as a backend

SwiftShader, if available, can be used by by exporting the VK_ICD_FILENAMES environment variable and using it directly. If SwiftShader is not installed it can be built with Amber by setting AMBER_ENABLE_SWIFTSHADER during the configure step of CMake.

mkdir out/sw
cd out/sw
export VK_ICD_FILENAMES=$PWD/Linux/vk_swiftshader_icd.json
./amber -d -V    # Should see SwiftShader listed as device
./amber -d ../../tests/cases/clear.amber

Amber Samples

The build will generate an out/Debug/amber executable which can be used to run amber scripts. The script can be used as out/Debug/amber <path to amber file>.

out/Debug/amber tests/cases/clear.amber

The sample app returns a value of 0 on success or non-zero on error. Any issues encountered should be displayed on the console.

Run out/Debug/amber -h to see a description of the program's command line options.

Example AmberScript files can be found in the tests/cases directory in this repository. Also the Vulkan Conformance Test Suite contains many real-world examples in its external/vulkancts/data/vulkan/amber subdirectory.

By default, out/Debug/amber supports saving the output image into '.png' file. You can disable this by passing -DAMBER_SKIP_LODEPNG=true to cmake.

The image_diff program will also be created. This allows comparing two images using the Amber buffer comparison methods.


Please see the CONTRIBUTING and CODE_OF_CONDUCT files on how to contribute to Amber.