From 3a70a43920fef877ade60d11e6b9fe9003ec54c9 Mon Sep 17 00:00:00 2001
From: Mikola Lysenko <mikolalysenko@gmail.com>
Date: Fri, 20 Jun 2014 16:36:21 -0400
Subject: [PATCH] adding files

---
 .gitignore         | 16 +++++++++++++
 README.md          | 55 +++++++++++++++++++++++++++++++++++++++++++++
 example/example.js | 41 +++++++++++++++++++++++++++++++++
 index.glsl         | 28 +++++++++++++++++++++++
 index.js           | 56 ++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 196 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 README.md
 create mode 100644 example/example.js
 create mode 100644 index.glsl
 create mode 100644 index.js

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ddc9ab3
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,16 @@
+lib-cov
+*.seed
+*.log
+*.csv
+*.dat
+*.out
+*.pid
+*.gz
+
+pids
+logs
+results
+
+npm-debug.log
+node_modules/*
+*.DS_Store
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..5eaa9e0
--- /dev/null
+++ b/README.md
@@ -0,0 +1,55 @@
+glsl-read-float
+===============
+Workaround for reading floating point values back from the GPU using GLSL.
+
+## Example
+
+```javascript
+```
+
+## Install
+
+```
+npm install glsl-read-float
+```
+
+## API
+
+### GLSL
+
+```glsl
+#pragma glslify: packFloat = require(glsl-read-float)
+```
+
+#### `vec4 packed = packFloat(float f)`
+Packs a floating point number into an 8bit RGBA color vector, which can be written to the display using `gl_FragColor`, for example.
+
+* `f` is a `float` number
+
+**Returns** A packed `vec4` encoding the value of `f`
+
+### JavaScript
+
+```javascript
+var unpackFloat = require("glsl-read-float")
+```
+
+#### `var f = readFloat(x, y, z, w)`
+Unpacks a packed `vec4` into a single floating point value.
+
+* `x` is the first component of the packed float
+* `y` is the second component of the packed float
+* `z` is the third component of the packed float
+* `w` is the fourth component of the packed float
+
+**Returns** A number which is the unpacked value of the floating point input.
+
+## Credits
+
+This routine was originally written by @ultraist.  You can find his blog here: http://ultraist.hatenablog.com/
+
+The post describing this code was published here:
+
+[WebGL GPGPUでfloatの結果を得る](http://ultraist.hatenablog.com/entry/20110608/1307539319)
+
+The npm entry and glslify packaging are currently maintained by Mikola Lysenko.
\ No newline at end of file
diff --git a/example/example.js b/example/example.js
new file mode 100644
index 0000000..42a1243
--- /dev/null
+++ b/example/example.js
@@ -0,0 +1,41 @@
+"use strict"
+
+var triangle     = require('a-big-triangle')
+var fit          = require('canvas-fit')
+var getContext   = require('gl-context')
+var createShader = require('glslify')
+var unpackFloat  = require("../index.js")
+
+var canvas     = container.appendChild(document.createElement('canvas'))
+var gl         = getContext(canvas, render)
+
+window.addEventListener('resize', fit(canvas), false)
+
+var shader = glslify({
+  vert: "\
+attribute vec2 position;\
+void main() {\
+  gl_Position = vec4(position, 0, 1);\
+}",
+  frag: "\
+uniform highp float f;\
+#pragma glslify: packFloat = require(../index.glsl)\
+void main() {\
+  gl_FragColor = packFloat(f);\
+}"})(gl)
+
+function render() {
+  var num = Math.random()
+
+  //Draw shader
+  shader.bind()
+  shader.uniforms.f = num
+  triangle(gl)
+
+  //Read back the float
+  var buffer = new Uint8Array(4)
+  gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buffer)
+
+  //Log output to console
+  console.log("expected:", num, "got:", )
+}
\ No newline at end of file
diff --git a/index.glsl b/index.glsl
new file mode 100644
index 0000000..b0d7945
--- /dev/null
+++ b/index.glsl
@@ -0,0 +1,28 @@
+vec4 nvjs_encode_float(float v) {
+  vec4 c = vec4(0.0, 0.0, 0.0, 0.0);
+  if (v < 0.0) {
+    c[0] += 64.0;
+    v = -v;
+  }
+  float f = 0.0;
+  float e = ceil(log2(v));
+  float m = v * exp2(-e);
+  if (e < 0.0) {
+    e = -e;
+    c[0] += 128.0;
+  }
+  c[0] += e;
+  m *= 255.0;
+  f = floor(m);
+  c[1] = f;
+  m  -= f;
+  m *= 255.0;
+  f = floor(m);
+  c[2] = f;
+  m  -= f;
+  m *= 255.0;
+  c[3] = floor(m);
+  return c * 3.921569E-03;
+}
+
+#pragma glslify: export(nvjs_encode_float)
\ No newline at end of file
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..6948c0a
--- /dev/null
+++ b/index.js
@@ -0,0 +1,56 @@
+//Adapted from here:  http://ultraist.hatenablog.com/entry/20110608/1307539319
+module.exports = decodeFloat
+
+var exp2_table = [
+   2.168404E-19, 4.336809E-19, 8.673617E-19, 1.734723E-18,
+   3.469447E-18, 6.938894E-18, 1.387779E-17, 2.775558E-17,
+   5.551115E-17, 1.110223E-16, 2.220446E-16, 4.440892E-16,
+   8.881784E-16, 1.776357E-15, 3.552714E-15, 7.105427E-15,
+   1.421085E-14, 2.842171E-14, 5.684342E-14, 1.136868E-13,
+   2.273737E-13, 4.547474E-13, 9.094947E-13, 1.818989E-12,
+   3.637979E-12, 7.275958E-12, 1.455192E-11, 2.910383E-11,
+   5.820766E-11, 1.164153E-10, 2.328306E-10, 4.656613E-10,
+   9.313226E-10, 1.862645E-09, 3.725290E-09, 7.450581E-09,
+   1.490116E-08, 2.980232E-08, 5.960464E-08, 1.192093E-07,
+   2.384186E-07, 4.768372E-07, 9.536743E-07, 1.907349E-06,
+   3.814697E-06, 7.629395E-06, 1.525879E-05, 3.051758E-05,
+   6.103516E-05, 1.220703E-04, 2.441406E-04, 4.882812E-04,
+   9.765625E-04, 1.953125E-03, 3.906250E-03, 7.812500E-03,
+   1.562500E-02, 3.125000E-02, 6.250000E-02, 1.250000E-01,
+   2.500000E-01, 5.000000E-01, 1.000000E+00, 2.000000E+00,
+   4.000000E+00, 8.000000E+00, 1.600000E+01, 3.200000E+01,
+   6.400000E+01, 1.280000E+02, 2.560000E+02, 5.120000E+02,
+   1.024000E+03, 2.048000E+03, 4.096000E+03, 8.192000E+03,
+   1.638400E+04, 3.276800E+04, 6.553600E+04, 1.310720E+05,
+   2.621440E+05, 5.242880E+05, 1.048576E+06, 2.097152E+06,
+   4.194304E+06, 8.388608E+06, 1.677722E+07, 3.355443E+07,
+   6.710886E+07, 1.342177E+08, 2.684355E+08, 5.368709E+08,
+   1.073742E+09, 2.147484E+09, 4.294967E+09, 8.589935E+09,
+   1.717987E+10, 3.435974E+10, 6.871948E+10, 1.374390E+11,
+   2.748779E+11, 5.497558E+11, 1.099512E+12, 2.199023E+12,
+   4.398047E+12, 8.796093E+12, 1.759219E+13, 3.518437E+13,
+   7.036874E+13, 1.407375E+14, 2.814750E+14, 5.629500E+14,
+   1.125900E+15, 2.251800E+15, 4.503600E+15, 9.007199E+15,
+   1.801440E+16, 3.602880E+16, 7.205759E+16, 1.441152E+17,
+   2.882304E+17, 5.764608E+17, 1.152922E+18, 2.305843E+18
+]
+
+function decodeFloat(x, y, z, w) {
+  var m = y * 3.921569E-03
+        + z * 1.537870E-05
+        + w * 6.030863E-08
+  var e = x
+  var i_sign = 0
+  if  (e & 0x80) {
+      i_sign = 1
+      e &= ~0x80
+  }
+  if (e & 0x40) {
+      m = -m
+      e &= ~0x40
+  }
+  if (i_sign) {
+      e = -e
+  }
+  return m * exp2_table[e + 62]
+}
\ No newline at end of file