Throughout college, suffice to say, I didn’t sleep much. If you know me well, you probably know the myriad reasons for this.<\/p>\n
Nowadays, artificial lighting can cause the Dim-Light Melatonin Offset to be pushed back. Anyone who has lived on a farm or near a construction site knows that until recently, the light of the sun was the only light by which we could work, and our bodies adjusted accordingly.<\/p>\n
It’s not much of a surprise, then, that staring into the bright light known as a “monitor” can impact some people’s sleep schedule vastly. It’s supplanted by the fact that for many people, night time frees them from the distractions of the day – people and the world outside in general.<\/p>\n
I was fortunate enough to find an application for my Mac called Nocturne<\/a> (from the makers of Quicksilver, in fact). It inverts the colors and can even tint a monochromed version of the inverted image – think green or amber terminal. An amber tint removes the blue light<\/a> that is known to principally inhibit the production of melatonin, setting your monitor to this amber-on-black setting in the evening may help things out.<\/p>\n Compiz provides many of the shiny effects on Ubuntu. The CompizConfig Settings Manager (not installed by default – check apt) has a color filter plugin available primarily for those with colorblindness. However, negative and negative-green options are provided for low-light computing. Green is a nice choice, but amber will give us the best results. Unfortunately, there’s no easy way to set the tint from CompizConfig.<\/p>\n The filter configurations are hidden away in the<\/p>\n folder. let’s check out the source for negative-green:<\/p>\n This is no GLSL<\/a>, folks. This is the real deal: ARB OpenGL Assembly Language<\/a> – specifically, a fragment program. It probably looks somewhat familiar if you’ve seen x86 or RISC assembly before.<\/p>\n I won’t say the approach used to invert the pixels is trivial, but we can eventually spot where the green tint is being applied:<\/p>\n This line takes the vector temp, subtracts temp (yielding the zero vector), and stores it in the .rb component of temp. Because temp is a color vector, the r and b stand for red and blue, leaving only the green component and alpha component intact.<\/p>\n Converting this to be a pure-red filter is simple enough – we’ll just subtract green instead of red and be set:<\/p>\n This makes a very nice red tinted inverted filter.<\/p>\n Next, of course, I wanted it a bit dimmer – 100% red is still fairly blinding in the dark. Easy, except for the catch with open source:<\/p>\n Modifying someone else’s code is one thing. Writing your own is different.<\/p>\n I honestly had no idea what I was doing in ARB, but RenderGuild kindly provides an ARB assembly quick reference<\/a>. Multiplying the .r component of my color seemed like the right thing to do, and to an extent, I was right. I also now believe that the alpha component (.a) has to be dimmed. Based on those two needs, I came up with these two instructions:<\/p>\n Perhaps there needs to only be one or the other, and perhaps they could be combined into a single instruction. It does, however, work to my liking.<\/p>\n Mac OS X’s OpenGL Shader Builder<\/a> was invaluable to checking the compilation of my sloppy coding and, more importantly, hinting at why it was wrong.<\/p>\n While I was working on the shader, I had some strange things such as near-all-red and near-all-black displays happen, with fading at the corners. I’m unsure why this happens, and may be a bug. Cycling back through again usually puts you back where you expect to be.<\/p>\n Here’s the source to my fragment shader. It can be downloaded here<\/a>.<\/p>\n I experimented with this kind of filtering during college starting at about 22h00 with a regular bedtime between 00h00 and 01h00. Now that I need to be sleeping sooner, I’ll likely push that back to… whenever sunset is.<\/p>\n This isn’t the solve-all for my sleep problems. Waking is still difficult to predict – blackout drapes are necessary for me to sleep, and therefore the natural light cues are absent for waking. With an alarm, I wake up to a dark vacuous room, which isn’t hugely motivating. I’ll be experimenting with an iPhone app (Climate) and perhaps building a gradual-wake LED light with my Arduino.<\/p>\n However, it has helped, and hopefully it can help someone else too.<\/p>\n","protected":false},"excerpt":{"rendered":" Throughout college, suffice to say, I didn’t sleep much. If you know me well, you probably know the myriad reasons for this. Nowadays, artificial lighting can cause the Dim-Light Melatonin Offset to be pushed back. Anyone who has lived on a farm or near a construction site knows that until recently, the light of the … Continue reading towards a good night’s rest<\/span> amber on linux<\/h2>\n
doing things the linux way<\/h3>\n
or, an adventure in OpenGL ARB fragment programs.<\/h4>\n
\/usr\/share\/compiz\/filters<\/pre>\n
!!ARBfp1.0
\nTEMP temp, neg;
\nTEX temp, fragment.texcoord[0], texture[0], RECT;
\nRCP neg.a, temp.a;
\nMAD temp.rgb, -neg.a, temp, 1.0;
\nMUL temp.rgb, temp.a, temp;
\nMUL temp, fragment.color, temp;
\nSUB temp.rb, temp, temp;
\nMOV result.color, temp;
\nEND<\/code><\/p><\/blockquote>\nSUB temp.rb, temp, temp;<\/code><\/p><\/blockquote>\nSUB temp.gb, temp, temp;<\/code><\/p><\/blockquote>\ninevitable last 2% difficulty<\/h3>\n
MUL tempColor.a, 0.6, tempColor.a;
\nMUL tempColor.r, 0.6, tempColor.r;<\/code><\/p><\/blockquote>\nnotes on writing shaders<\/h3>\n
notes on Compiz filter switching<\/h3>\n
the grand results<\/h1>\n
!!ARBfp1.0
\nTEMP tempColor, negColor;
\nTEX tempColor, fragment.texcoord[0], texture[0], RECT;
\nRCP negColor.a, tempColor.a;
\nMAD tempColor.rgb, -negColor.a, tempColor, 1.0;
\nMUL tempColor.rgb, tempColor.a, tempColor;
\nMUL tempColor, fragment.color, tempColor;
\nSUB tempColor.gb, tempColor, tempColor;
\n# here is where we will dim.
\nMUL tempColor.a, .6, tempColor.a;
\nMUL tempColor.r, 0.6, tempColor.r;
\nMOV result.color, tempColor;
\nEND<\/code><\/p><\/blockquote>\nendnotes<\/h2>\n