spine-runtimes/spine-glfw/docs.md

spine-glfw Runtime Documentation

Licensing

Please see the Spine Runtimes License before integrating the Spine Runtimes into your applications.

Getting Started

spine-glfw is a C++ based runtime to load, manipulate and render Spine skeletons with GLFW and OpenGL.

spine-glfw requires GLFW 3.0+ and OpenGL 3.3+ and supports all Spine features including two-color tinting.

Installation

The spine-glfw runtime is available as a C++ API based on the generic spine-cpp runtime and also supports spine-c API. To integrate spine-glfw into your project:

1. Create a new GLFW project. See the GLFW documentation or have a look at the example in spine-runtimes repository, which uses CMake as the build system.
2. Download the Spine Runtimes source using git (git clone https://github.com/esotericsoftware/spine-runtimes).
3. Add the sources from spine-cpp/spine-cpp/src/spine and the files spine-glfw/src/spine-glfw.cpp and spine-glfw/src/spine-glfw.h to your project.
4. Add the folders spine-cpp/spine-cpp/include and spine-glfw/src to your header search path.
5. Link against GLFW, OpenGL, and optionally glbinding for modern OpenGL function loading.

In your C++ code, include the following header file to get access to the spine-glfw API:

#include <spine-glfw.h>

Note: spine-glfw requires OpenGL 3.3 Core Profile or higher. The runtime uses modern OpenGL features including vertex array objects, vertex buffer objects, and GLSL shaders.

Samples

The spine-glfw example works on Windows, Linux and Mac OS X. For a spine-cpp based example, see example/main.cpp, for a spine-c example see example/main-c.cpp.

Windows

1. Install Visual Studio Community. Make sure you install support for C++ and CMake.
2. Download the Spine Runtimes repository using git (git clone https://github.com/esotericsoftware/spine-runtimes) or download it as a zip.
3. Open Visual Studio Community, then open spine-glfw/ via the Open a local folder button in the Visual Studio Community launcher.
4. Wait for CMake to finish, then select either spine-glfw-example.exe or spine-glfw-example-c.exe as the start-up project and start debugging.

Linux

1. Install dependencies:

   sudo apt-get install cmake ninja-build libgl1-mesa-dev libx11-dev libxrandr-dev libxinerama-dev libxcursor-dev libxi-dev  # Ubuntu/Debian
   # or equivalent for your distribution
   

2. Clone the repository: git clone https://github.com/esotericsoftware/spine-runtimes
3. Build and run:

   cd spine-runtimes/spine-glfw
   ./build.sh
   ./build/debug/spine-glfw-example-c    # Run C example
   ./build/debug/spine-glfw-example      # Run C++ example
   

macOS

1. Install Xcode
2. Install Homebrew
3. Install dependencies:

   brew install cmake ninja
   

4. Clone the repository: git clone https://github.com/esotericsoftware/spine-runtimes
5. Build and run:

   cd spine-runtimes/spine-glfw
   ./build.sh
   ./build/debug/spine-glfw-example-c    # Run C example
   ./build/debug/spine-glfw-example      # Run C++ example
   

Using spine-glfw

The spine-glfw runtime supports playback and manipulation of animations created with Spine using GLFW and OpenGL. The spine-glfw runtime is implemented in C++ and is based on the generic spine-cpp runtime. It adds loading and rendering implementations based on OpenGL APIs.

Please consult the Spine Runtimes Guide for a detailed overview of the Spine Runtime architecture, and the spine-cpp documentation for information on the core APIs used to playback and manipulate animations created with Spine with C++.

Exporting for GLFW

Please follow the instructions in the Spine User Guide on how to

1. Export skeleton & animation data
2. Export texture atlases containing the images of your skeleton

An export of the skeleton data and texture atlas of your skeleton will yield the following files:

1. skeleton-name.json or skeleton-name.skel, containing your skeleton and animation data.
2. skeleton-name.atlas, containing information about the texture atlas.
3. One or more .png files, each representing on page of your texture atlas containing the packed images your skeleton uses.

Note: The spine-glfw runtime does not support the screen blend mode available in the Spine editor.

Loading Spine skeletons

The spine-glfw runtime uses OpenGL for rendering skeletons. Before a skeleton can be loaded from exported files, a GLFW window and OpenGL context must be created:

// Initialize GLFW
if (!glfwInit()) {
    // Handle error
    return -1;
}

// Set OpenGL version to 3.3 Core Profile
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

// Create window
GLFWwindow* window = glfwCreateWindow(800, 600, "Spine GLFW", NULL, NULL);
glfwMakeContextCurrent(window);

// Initialize OpenGL function loading (e.g., with glbinding)
glbinding::initialize(glfwGetProcAddress);

Next, the texture atlas can be loaded using the GlTextureLoader:

// C++ API
spine::GlTextureLoader textureLoader;
spine::Atlas *atlas = new spine::Atlas("data/spineboy-pma.atlas", &textureLoader);

With the atlas loaded, the .json or .skel file can be loaded:

// C++ API
spine::SkeletonBinary binary(atlas);
spine::SkeletonData *skeletonData = binary.readSkeletonDataFile("data/spineboy-pro.skel");

For JSON format:

// C++ API
spine::SkeletonJson json(atlas);
spine::SkeletonData *skeletonData = json.readSkeletonDataFile("data/spineboy-pro.json");

The spine::Atlas and spine::SkeletonData instances can then be used to create spine::Skeleton instances for rendering.

Note: the loaded skeleton data and atlas can and should be shared across spine::Skeleton instances to reduce memory consumption and enable batched rendering of skeletons that share the same atlas data.

Renderer

The main addition of spine-glfw on top of spine-cpp is the renderer system. The renderer handles the OpenGL rendering pipeline including shaders, meshes, and textures. Unlike other runtimes that provide a drawable class, spine-glfw uses a more modular approach with separate renderer and mesh components.

You can create a renderer like this:

// Create the renderer and set viewport size
renderer_t *renderer = renderer_create();
renderer_set_viewport_size(renderer, windowWidth, windowHeight);

The renderer automatically creates and manages OpenGL shaders optimized for Spine skeleton rendering.

Creating and animating skeletons

With the skeleton data loaded, you can create a skeleton instance:

// Set coordinate system (spine-glfw uses y-down by default)
spine::Bone::setYDown(true);

// Create a skeleton from the data
spine::Skeleton skeleton(skeletonData);
skeleton.setPosition(400, 500);
skeleton.setScaleX(0.5f);
skeleton.setScaleY(0.5f);

For animation, create an animation state:

// Create animation state
spine::AnimationStateData animationStateData(skeletonData);
animationStateData.setDefaultMix(0.2f);
spine::AnimationState animationState(&animationStateData);

// Set animations
animationState.setAnimation(0, "portal", true);
animationState.addAnimation(0, "run", true, 0);

Please refer to the spine-cpp documentation for more information on the APIs to manipulate skeletons and animation states.

Updating and rendering

In your main loop, update the animation state and skeleton, then render:

double lastTime = glfwGetTime();
while (!glfwWindowShouldClose(window)) {
    double currTime = glfwGetTime();
    float delta = currTime - lastTime;
    lastTime = currTime;

    // Update animation state
    animationState.update(delta);
    animationState.apply(skeleton);

    // Update skeleton
    skeleton.update(delta);
    skeleton.updateWorldTransform(spine::Physics_Update);

    // Clear screen
    gl::glClear(gl::GL_COLOR_BUFFER_BIT);

    // Render skeleton
    renderer_draw(renderer, &skeleton, true); // true for premultiplied alpha

    // Present
    glfwSwapBuffers(window);
    glfwPollEvents();
}

Using spine-c

spine-glfw also supports the spine-c API for applications that need a C interface or are written in programming languages that cannot interface with C++ code directly. The key differences when using spine-c with spine-glfw are:

Key Differences from spine-cpp:

1. C API instead of C++: All functions use C-style naming (e.g., spine_skeleton_set_position vs skeleton.setPosition)
2. Manual file loading: You must manually load atlas and skeleton files into memory
3. Callback-based texture loading: Textures are loaded via user-provided callback functions
4. Skeleton drawable wrapper: Uses spine_skeleton_drawable which wraps skeleton and animation state
5. Different renderer function: Uses renderer_draw_c() instead of renderer_draw()

Texture Loading with Callbacks

First, you need to provide texture loading callbacks that bridge spine-cpp-lite to spine-glfw's texture system:

// Callback function to load textures
void *load_texture(const char *path) {
    return (void *)(uintptr_t)texture_load(path);
}

// Callback function to unload textures
void unload_texture(void *texture) {
    texture_dispose((texture_t)(uintptr_t)texture);
}

Loading Atlas and Skeleton Data

Unlike spine-cpp which can load files directly, spine-c requires manual file reading:

// Read atlas file into memory
int atlas_length = 0;
uint8_t *atlas_bytes = read_file("data/spineboy-pma.atlas", &atlas_length);
spine_atlas atlas = spine_atlas_load_callback(
    (utf8*)atlas_bytes, "data/", load_texture, unload_texture);

// Read skeleton file into memory
int skeleton_length = 0;
uint8_t *skeleton_bytes = read_file("data/spineboy-pro.skel", &skeleton_length);
spine_skeleton_data_result result = spine_skeleton_data_load_binary(atlas, skeleton_bytes, skeleton_length);
spine_skeleton_data skeleton_data = spine_skeleton_data_result_get_data(result);

Creating and Manipulating Skeletons

spine-c uses a drawable wrapper and C-style function calls:

// Create skeleton drawable (combines skeleton + animation state)
spine_skeleton_drawable drawable = spine_skeleton_drawable_create(skeleton_data);
spine_skeleton skeleton = spine_skeleton_drawable_get_skeleton(drawable);

// Set skeleton properties using C functions
spine_skeleton_set_position(skeleton, width / 2, height - 100);
spine_skeleton_set_scale(skeleton, 0.3f, 0.3f);

// Get animation state from drawable
spine_animation_state animation_state = spine_skeleton_drawable_get_animation_state(drawable);
spine_animation_state_data animation_state_data = spine_animation_state_get_data(animation_state);
spine_animation_state_data_set_default_mix(animation_state_data, 0.2f);

// Set animations using C functions
spine_animation_state_set_animation_1(animation_state, 0, "portal", true);
spine_animation_state_add_animation_1(animation_state, 0, "run", true, 0);

Updating and Rendering

The update loop uses C-style function calls and a different renderer function:

// Update animation state and skeleton
spine_skeleton_drawable_update(drawable, deltaTimeInSeconds)

// Render using the C-specific function
renderer_draw_c(renderer, skeleton, true);

The renderer_draw_c() function is specifically designed to work with spine-c's spine_skeleton opaque type, while renderer_draw() works with spine-cpp's spine::Skeleton class.

Cleanup

Cleanup for spine-cpp

When using the spine-cpp API, use C++ delete operators:

// Dispose renderer
renderer_dispose(renderer);

// Dispose skeleton data and atlas (C++ API)
delete skeletonData;
delete atlas;

// Cleanup GLFW
glfwTerminate();

Cleanup for spine-c

When using the spine-c API, use the C-style dispose functions:

// Dispose renderer
renderer_dispose(renderer);

// Dispose skeleton data and atlas (C API)
spine_skeleton_drawable_dispose(drawable);
spine_skeleton_data_dispose(skeleton_data);
spine_atlas_dispose(atlas);

// Free manually allocated file data
free(atlas_bytes);
free(skeleton_bytes);

// Cleanup GLFW
glfwTerminate();

Note: freeing skeleton data and atlas instances will automatically dispose of any associated OpenGL textures through the texture loader. With spine-c, you must also free any memory you allocated for file data using malloc()/read_file().