# picogl.js

**Repository Path**: iloseall/picogl.js

## Basic Information

- **Project Name**: picogl.js
- **Description**: A minimal WebGL 2 rendering library
- **Primary Language**: JavaScript
- **License**: MIT
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-06-21
- **Last Updated**: 2021-07-03

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

PicoGL.js
========

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**[API Docs](https://tsherif.github.io/picogl.js/docs/)** | **[Tutorial](https://tsherif.wordpress.com/2017/07/26/webgl-2-development-with-picogl-js/)** | **[Chat](https://gitter.im/picogl-js/general)**

PicoGL.js is minimal WebGL 2 rendering library. It's meant for developers who understand the WebGL 2 rendering pipeline and want to use it, but with a more convenient API. Typical usage of PicoGL.js will involve creating programs, vertex buffers, vertex arrays, uniform buffers, framebuffers, textures, transform feedbacks, and combining them into draw calls.

```JavaScript

    // Create App which manages all GL state
    var app = PicoGL.createApp(canvas)
    .clearColor(0.0, 0.0, 0.0, 1.0);
    
    // Create Program
    var program = app.createProgram(vertexShaderSource, fragmentShaderSource);

    // Create a buffer of vertex attributes
    var positions = app.createVertexBuffer(PicoGL.FLOAT, 2, new Float32Array([
        -0.5, -0.5,
         0.5, -0.5,
         0.0,  0.5
    ]));

    // VertexArray manages attribute buffer state
    var vertexArray = app.createVertexArray()
    .vertexAttributeBuffer(0, positions);

    // UniformBuffer allows multiple uniforms to be bound
    // as a single block of memory.
    // First part defines layout of the UniformBuffer.
    // Second part updates values.
    var uniformBuffer = app.createUniformBuffer([
        PicoGL.FLOAT_VEC4,
        PicoGL.FLOAT_VEC4
    ])
    .set(0, new Float32Array([1.0, 0.0, 0.0, 0.3]))
    .set(1, new Float32Array([0.0, 0.0, 1.0, 0.7]))
    .update();

    // Create DrawCall from Program and VertexArray (both required),
    // and a UniformBuffer.
    var drawCall = app.createDrawCall(program, vertexArray)
    .uniformBlock("ColorUniforms", uniformBuffer);

    // Draw
    app.clear();
    drawCall.draw();

``` 

Note that PicoGL.js is **not** a scene graph library. There are no objects, hierarchies, transforms, materials, etc. It has been designed only to make management of GPU state more convenient. Its conceptual model maps fairly directly to the constructs one deals with when writing directly with the WebGL 2 API. The only higher-level construct is the **draw call**, which manages sets of related lower-level constructs.



Usage
-----
PicoGL.js can be used directly by downloading the [built source](https://tsherif.github.io/picogl.js/build/picogl.min.js) and loading it via a script tag:

```HTML
    <script src="js/picogl.min.js"></script>
```

or it can be installed via [npm](https://www.npmjs.com/package/picogl):

```bash
    npm install picogl
```

and loaded via CommonJS-style `require`:

```JavaScript
    var PicoGL = require("picogl");
```

Features
--------

PicoGL.js simplifies usage of some more complex WebGL 2 features, such as multiple render targets, uniform buffers, transform feedback and instanced drawing.

**Multiple Render Targets**

```JavaScript
    var app = PicoGL.createApp(canvas)
    .clearColor(0.0, 0.0, 0.0, 1.0);


    // Texture render targets
    var colorTarget0 = app.createTexture2D(app.width, app.height);
    var colorTarget1 = app.createTexture2D(app.width, app.height);
    var depthTarget = app.createTexture2D(app.width, app.height, {
        format: PicoGL.DEPTH_COMPONENT
    });


    // Create framebuffer with color targets at attachments 
    // 0 and 1, and a depth target.
    var framebuffer = app.createFramebuffer()
    .colorTarget(0, colorTarget0)
    .colorTarget(1, colorTarget1)
    .depthTarget(depthTarget);
    
    // ... set up programs and vertex arrays for offscreen and
    // main draw passes...
    
    var offscreenDrawCall = app.createDrawCall(offscreenProgram, offscreenVAO);

    // Bind main program texture samplers to framebuffer targets
    var mainDrawCall = app.createDrawCall(mainProgram, mainVAO)
    .texture("texture1", framebuffer.colorAttachments[0])
    .texture("texture2", framebuffer.colorAttachments[1])
    .texture("depthTexture", framebuffer.depthAttachment);

    // Offscreen pass
    app.drawFramebuffer(framebuffer).clear();
    offscreenDrawCall.draw();
    
    // Main draw pass
    app.defaultDrawFramebuffer().clear()
    mainDrawCall.draw();
```

**Uniform Buffers**

```JavaScript
    var app = PicoGL.createApp(canvas)
    .clearColor(0.0, 0.0, 0.0, 1.0);
    
    // ... set up program and vertex array...

    // Layout is std140
    var uniformBuffer = app.createUniformBuffer([
        PicoGL.FLOAT_MAT4,
        PicoGL.FLOAT_VEC4,
        PicoGL.INT_VEC4,
        PicoGL.FLOAT
    ])
    .set(0, matrix)
    .set(1, float32Vector)
    .set(2, int32Vector)
    .set(3, scalar)
    .update();      // Data only sent to GPU when update() is called

    var drawCall = app.createDrawCall(program, vertexArray)
    .uniformBlock("UniformBlock", uniformBuffer);
```

**Transform Feedback**

```JavaScript
    var app = PicoGL.createApp(canvas)
    .clearColor(0.0, 0.0, 0.0, 1.0);

    // Last argument is transform feedback varyings
    var program = app.createProgram(vertexShaderSource, fragmentShaderSource, ["vPosition"]);

    var positions1 = app.createVertexBuffer(PicoGL.FLOAT, 2, new Float32Array([
        -0.5, -0.5,
         0.5, -0.5,
         0.0,  0.5
    ]));
    var vertexArray = app.createVertexArray()
    .vertexAttributeBuffer(0, positions1);

    // Empty destination buffer of 6 floats
    var positions2 = app.createVertexBuffer(PicoGL.FLOAT, 2, 6);  

    // Capture transform results into positions2 buffer
    var transformFeedback = app.createTransformFeedback()
    .feedbackBuffer(0, positions2);

    var drawCall = app.createDrawCall(program, vertexArray)
    .transformFeedback(transformFeedback);

    app.clear();
    drawCall.draw();

``` 

**Instanced Drawing**

```JavaScript
    var app = PicoGL.createApp(canvas)
    .clearColor(0.0, 0.0, 0.0, 1.0);

    var program = app.createProgram(vertexShaderSource, fragmentShaderSource);

    // The starting positions of the triangle. Each pair of coordinates
    // will be passed per-vertex
    var positions = app.createVertexBuffer(PicoGL.FLOAT, 2, new Float32Array([
        -0.3, -0.3,
         0.3, -0.3,
         0.0,  0.3
    ]));

    // This is an instance buffer meaning each pair of numbers will be passed
    // per-instance, rather than per-vertex
    var offsets = app.createVertexBuffer(PicoGL.FLOAT, 2, new Float32Array([
        -0.5, 0.0,
         0.0, 0.2,
         0.5, 0.0
    ]));

    // This vertex array is set up to draw 3 instanced triangles 
    // with the offsets given above
    var vertexArray = app.createVertexArray()
    .vertexAttributeBuffer(0, positions); // Pass positions per-vertex
    .instanceAttributeBuffer(1, offset); // Pass offsets per-instance
```