gl-fbo
======
WebGL framebuffer object wrapper

Example

Try this in your browser if you have WebGL

``javascript
var shell = require("gl-now")()
var createFBO = require("gl-fbo")
var glslify = require("glslify")
var ndarray = require("ndarray")
var fill = require("ndarray-fill")
var fillScreen = require("a-big-triangle")

var createUpdateShader = glslify({
vertex: "\
attribute vec2 position;\
varying vec2 uv;\
void main() {\
gl_Position = vec4(position,0.0,1.0);\
uv = 0.5 * (position+1.0);\
}",
fragment: "\
precision mediump float;\
uniform sampler2D buffer;\
uniform vec2 dims;\
varying vec2 uv;\
void main() {\
float n = 0.0;\
for(int dx=-1; dx<=1; ++dx)\
for(int dy=-1; dy<=1; ++dy) {\
n += texture2D(buffer, uv+vec2(dx,dy)/dims).r;\
}\
float s = texture2D(buffer, uv).r;\
if(n > 3.0+s || n < 3.0) {\
gl_FragColor = vec4(0,0,0,1);\
} else {\
gl_FragColor = vec4(1,1,1,1);\
}\
}",
inline: true
})

var createDrawShader = glslify({
vertex: "\
attribute vec2 position;\
varying vec2 uv;\
void main() {\
gl_Position = vec4(position,0.0,1.0);\
uv = 0.5 * (position+1.0);\
}",
fragment: "\
precision mediump float;\
uniform sampler2D buffer;\
varying vec2 uv;\
void main() {\
gl_FragColor = texture2D(buffer, uv);\
}",
inline: true
})

var state, updateShader, drawShader, current = 0

shell.on("gl-init", function() {
var gl = shell.gl

//Turn off depth test
gl.disable(gl.DEPTH_TEST)

//Initialize shaders
updateShader = createUpdateShader(gl)
drawShader = createDrawShader(gl)

//Allocate buffers
state = [ createFBO(gl, [512, 512]), createFBO(gl, [512, 512]) ]

//Initialize state buffer
var initial_conditions = ndarray(new Uint8Array(5125124), [512, 512, 4])
fill(initial_conditions, function(x,y,c) {
if(c === 3) {
return 255
}
return Math.random() > 0.9 ? 255 : 0
})
state[0].color[0].setPixels(initial_conditions)

//Set up vertex pointers
drawShader.attributes.position.location = updateShader.attributes.position.location = 0
})

shell.on("tick", function() {
var gl = shell.gl
var prevState = state[current]
var curState = state[current ^= 1]

//Switch to state fbo
curState.bind()

//Run update shader
updateShader.bind()
updateShader.uniforms.buffer = prevState.color[0].bind()
updateShader.uniforms.dims = prevState.shape
fillScreen(gl)
})

shell.on("gl-render", function(t) {
var gl = shell.gl

//Render contents of buffer to screen
drawShader.bind()
drawShader.uniforms.buffer = state[current].color[0].bind()
fillScreen(gl)
})
`

Result:




Install

Install using npm:

npm install gl-fbo

API

$3

Constructor

There is currently only one default way to create a Framebuffer object. You can construct a framebuffer using the following syntax:

$3

Creates a wrapped framebuffer object

* gl is a handle to a WebGL context
* shape is a length 2 array encoding the [width, height] of the frame buffer
* options is an object containing the following optional properties:

+ options.preferFloat Upgrade to floating point if available, otherwise fallback to 8bit. (default false)
+ options.float Use floating point textures (default false)
+ options.color The number of color buffers to create (default 1)
+ options.depth If fbo has a depth buffer (default: true)
+ options.stencil If fbo has a stencil buffer (default: false)

Methods

$3

Binds the framebuffer object to the display. To rebind the original drawing buffer, you can just call WebGL directly:

`javascript
//Bind the drawing buffer
gl.bindFramebuffer(gl.FRAMEBUFFER, null)
`

$3

Destroys the framebuffer object and releases all associated resources

Properties

$3

Returns the shape of the frame buffer object. Writing to this property resizes the framebuffer. For example,

`javascript
fbo.shape = [ newWidth, newHeight ]
`

$3

A reference to the WebGL context

$3

A handle to the underlying Framebuffer object.

$3

An array containing gl-texture2d objects representing the buffers.

$3

The depth/stencil component of the FBO. Stored as a gl-texture2d. If not present, is null`.

Credits
=======
(c) 2013-2014 Mikola Lysenko. MIT License