PixiJS Batch Rendering Library

pixi-batch-renderer is a PixiJS plugin that allows you to add batch rendering to your custom display objects. I have documented each class in the PIXI.brend namespace.

Concepts

Batch rendering objects involves aggregating them into groups/batches and rendering them together with one WebGL draw call. PixiJS supports batch rendering its internal display objects - PIXI.Sprite, PIXI.Graphics, and PIXI.Mesh. However, it is difficult to extend that to custom-built display objects; it wasn't designed as an exposable API.

This library builds upon the same concept and is designed for maximum flexibility. It still uses PixiJS's batch system - a stub that enables objects to be rendered asynchronously, without loosing the order of rendering. To understand how it works, understanding these things are helpful:

* Attribute Redirects: An attribute redirect is a data-object that tells pixi-batch-renderer how it will transform your object into a set of shader attributes.

* Index Property: If you use indices, this will be property on your display object that holds those indices. It could also be a constant array, rather than a property on each object.

* State Function: This function/property tells the batch renderer what WebGL state is required to render a display-object. It is optional if you're display objects use the default state (PIXI.State.for2d()).

* Shader Function: This function generates the shader to render whole batches. It takes one argument - the batch renderer
that will use the shader. You can use the BatchShaderFactory#derive() API for create one.

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* Shader Templates: The BatchShaderFactory allows you to write shader "templates" containing %macros%. At runtime, you
can replace these macros based with another expression. For example, the (built-in) %texturesPerBatch% macro is set to the
no. of textures units in the GPU.

* Custom uniforms: [Experimental] You can also use uniforms in the batch shader; however, this might reduce the batching
efficiency if most batchable display-objects have different values for uniforms (because then they can't be batched together).

* Modular architecture: With the modular architecture of this library, you change the behaviour of any component. The
geometry composition, batch generation, and drawing stages are componentized and can be modified by providing a custom
implementation to BatchRendererPluginFactory.from.

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Before rendering itself, a PIXI.Container with filters or a mask will flush the batch renderer and will not batch itself. This
is because the PixiJS batch renderer cannot batch filtered and masked objects. Although this does not break pixi-batch-renderer,
it does reduce batching-efficiency. If you want to create a batch renderer that will batch filtered and masked objects too, your display-object must override render (however, you will have to derive your own batch renderer class for that):

``
render(renderer: PIXI.Renderer): void
{
// If you registered the batch renderer as a plugin "pluginName", then replace with
// renderer.plugins.pluginName
renderer.setObjectRenderer();
.render(this);

for (let i = 0, j = this.children.length; i < j; i++)
{
this._children.render(renderer);
}
}
`

Usage

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For most use cases, PIXI.brend.BatchRendererPluginFactory is all you'll need from this library. You need to do these three things:

1. Generate the plugin class using PIXI.brend.BatchRendererPluginFactory.from

2. Register the plugin with PixiJS's WebGL renderer

3. Make your custom display object defer its rendering to your plugin

An example implementation would look like:

`js
import * as PIXI from 'pixi.js';
import { AttributeRedirect, BatchRendererPluginFactory, BatchShaderFactory } from 'pixi-batch-renderer';

// ExampleFigure has two attributes: aVertex and aTextureCoord. They come from the
// vertices and uvs properties in this object. The indices are in the indices property.
class ExampleFigure extends PIXI.Container
{
_render(renderer)
{
this.vertices = [x0,y0, x1,y1, x2,y2, ..., xn,yn];// variable number of vertices
this.uvs = [u0,v0, u1,v1, u2, v2, ..., un,yn];// however, all other attributes must have equal length
this.texture = PIXI.Texture.from("url:example");

this.indices = [0, 1, 2, ..., n];// we could also tell our batch renderer to not use indices too :)

renderer.setObjectRenderer(renderer.plugins["ExampleRenderer"]);
renderer.plugins["ExampleRenderer"].render(this);
}
}

// Define the geometry of ExampleFigure.
const attribSet = [
new AttributeRedirect({
source: "vertices",
attrib: "aVertex",
type: 'float32',
size: 2,
glType: PIXI.TYPES.FLOAT,
glSize: 2
}),
new AttributeRedirect({
source: "uvs",
attrib: "aTextureCoord",
type: 'float32',
size: 2,
glType: PIXI.TYPES.FLOAT,
size: 2
}),
];

// Create a shader function from a shader template!
const shaderFunction = new BatchShaderFactory(
// Vertex Shader

attribute vec2 aVertex;
attribute vec2 aTextureCoord;
attribute float aTextureId;

varying float vTextureId;
varying vec2 vTextureCoord;

uniform mat3 projectionMatrix;

void main()
{
gl_Position = vec4((projectionMatrix * vec3(aVertex.xy, 1)), 0, 1);
vTextureId = aTextureId;
vTextureCoord = aTextureCoord;
}
,

// Fragment Shader

uniform uSamplers[%texturesPerBatch%];/ %texturesPerBatch% is a macro and will become a number /\
varying float vTextureId;
varying vec2 vTextureCoord;

void main(void){
vec4 color;

/ get color, which is the pixel in texture uSamplers[vTextureId] @ vTextureCoord /
for (int k = 0; k < %texturesPerBatch%; ++k)
{
if (int(vTextureId) == k)
color = texture2D(uSamplers[k], vTextureCoord);

}

gl_FragColor = color;
}
,
{}).derive();

// Create batch renderer class
const ExampleRenderer = BatchRendererPluginFactory.from({
attribSet,
indexProperty: "indices",
textureProperty: "texture",
texIDAttrib: "aTextureId", // this will be used to locate the texture in the fragment shader later
shaderFunction
});

// Remember to do this before instantiating a PIXI.Application or PIXI.Renderer!
PIXI.Renderer.registerPlugin("ExampleRenderer", ExampleRenderer);
`

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You can take advantage of shader uniforms in batching too! pixi-batch-renderer supports this out of the box
with the AggregateUniformsBatchFactory. There are two modes for uniforms:

* Aggregation mode: Uniforms of each display-object are aggregated into an array. Then an uniform-ID attribute
is uploaded (say aUniformId) that tells the shader which uniform to pick out of an array. The attribute is passed
to the plugin factory via the uniformIDAttrib option.

* No-aggregation mode: Uniforms are uploaded in one-element arrays. Display-objects with different uniform values
are not batched together. This is useful if your uniform values don't differ a lot and will avoid another attribute. To
use this mode, simply don't pass an uniformIDAttrib.

1. Aggregation Mode (Example)

`js
const { UniformRedirect, AggregateUniformsBatchFactory } = require('pixi-batch-renderer');

const shaderFunction = new BatchShaderFactory(
// Vertex Shader

attribute vec2 aVertex;
attribute vec2 aTextureCoord;
attribute float aTextureId;
attribute float aUniformId;

varying float vTextureId;
varying vec2 vTextureCoord;
varying float vUniformId;

uniform mat3 projectionMatrix;

void main()
{
gl_Position = vec4((projectionMatrix * vec3(aVertex.xy, 1)), 0, 1);
vTextureId = aTextureId;
vTextureCoord = aTextureCoord;

vUniformId = aUniformId;
}
,

// Fragment Shader

// You can also use this in the vertex shader.
uniform shaderType[%uniformsPerBatch%];
varying float vUniformId;

uniform uSamplers[%texturesPerBatch%];/ %texturesPerBatch% is a macro and will become a number /\
varying float vTextureId;
varying vec2 vTextureCoord;

void main(void){
vec4 color;
float type;

/ get color & shaderType /
for (int k = 0; k < int(max(%texturesPerBatch%., %uniformsPerBatch%.)); ++k)
{
if (int(vTextureId) == k) {
color = texture2D(uSamplers[k], vTextureCoord);
}
if (int(vUniformId) == k) {
type = shaderType[vUniformId];
}
}

if (type == 1)
{
gl_FragColor = color;
}
else
{
gl_FragColor = vec4(color.rgb * vTextureCoord.x, vTextureCoord.x);
}
}
,
{}).derive();

const uniformSet = [
new UniformRedirect({ source: "type", uniform: "shadingType" });
];

const ExampleRenderer = BatchRendererPluginFactory.from({
uniformSet,
uniformIDAttrib: "aUniformId",

// Previous example's stuff
attribSet,
indexProperty: "indices",
textureProperty: "texture",
texIDAttrib: "aTextureId",
shaderFunction,

BatchFactoryClass: AggregateUniformsBatchFactory
})
`

2. No Aggregation Mode (Example)


`js
const { UniformRedirect, AggregateUniformsBatchFactory } = require('pixi-batch-renderer');

const shaderFunction = new BatchShaderFactory(
// Vertex Shader (no changes to standard pipeline example!)

attribute vec2 aVertex;
attribute vec2 aTextureCoord;
attribute float aTextureId;
varying float vTextureId;
varying vec2 vTextureCoord;

uniform mat3 projectionMatrix;

void main()
{
gl_Position = vec4((projectionMatrix * vec3(aVertex.xy, 1)), 0, 1);
vTextureId = aTextureId;
vTextureCoord = aTextureCoord;
}
,

// Fragment Shader

// Look only one-element instead of %uniformsPerBatch%
uniform shaderType[1];
varying float vUniformId;

uniform uSamplers[%texturesPerBatch%];/ %texturesPerBatch% is a macro and will become a number /\
varying float vTextureId;
varying vec2 vTextureCoord;

void main(void){
vec4 color;
float type = shaderType;

/ get color & shaderType /
for (int k = 0; k < %texturesPerBatch%; ++k)
{
if (int(vTextureId) == k) {
color = texture2D(uSamplers[k], vTextureCoord);
}
}

if (type == 1)
{
gl_FragColor = color;
}
else
{
gl_FragColor = vec4(color.rgb * vTextureCoord.x, vTextureCoord.x);
}
}
,
{}).derive();

const uniformSet = [
new UniformRedirect({ source: "type", uniform: "shaderType" });
];

const ExampleRenderer = BatchRendererPluginFactory.from({
uniformSet,

attribSet,
indexProperty: "indices",
textureProperty: "texture",
texIDAttrib: "aTextureId",
shaderFunction,

BatchFactoryClass: AggregateUniformsBatchFactory
});

PIXI.Renderer.registerPlugin("erend", ExampleRenderer);

// Try using with a Sprite!
const sprite = PIXI.Sprite.from();

sprite.pluginName = "erend";
sprite.type = 0;// will fade out horizontally in shader
`

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The BatchRendererPluginFactory.from method also accepts these (optional) options that can be used to extend the
behaviour of built-in components:

* BatchFactoryClass: Child class of [StdBatchFactory]{@link https://pixijs.io/pixi-batch-renderer/PIXI.brend.StdBatchFactory.html}

* BatchGeometryClass: Child class of [BatchGeometry]{@link https://pixijs.io/pixi-batch-renderer/PIXI.brend.BatchGeometryFactory.html}

* BatchDrawerClass: Child class of [BatchDrawer]{@link https://pixijs.io/pixi-batch-renderer/PIXI.brend.BatchDrawer.html}

* BatchRendererClass`: If overriding a component does not meet your requirements, you can derive your own batch renderer by
providing a child class of [BatchRenderer]{@link https://pixijs.io/pixi-batch-renderer/PIXI.brend.BatchRenderer.html}