Proper Gradients for MetaPost Pulse Sequences

Proper Gradients for MetaPost Pulse Sequences

In which I improve upon the previous post...

In yesterday's post I talked about using MetaPost to generate Pulse Sequence Diagrams for MRI documents. I have been using this to make nice diagrams for my Thesis. There is one problem, however, with the pulse sequence file provided on Mark's website - it generates square gradients.

Pulse Sequence Diagrams Using Metapost

Pulse Sequence Diagrams Using Metapost

In which I use MetaPost to generate publication quality pulse sequence diagrams...

Pulse sequences are the series of radio-frequency pulses required to generate an MR image. If you are an MR Physicist you will see these a lot and probably wondered how can I generate nice pulse sequences for my thesis, papers etc. Well handily using MetaPost and these files you can!

Steam on (Gentoo) Linux

Steam on (Gentoo) Linux

In which I install Steam on Linux...

Steam is now officially supported on Linux! I decided to try it out.

Hold your horses!

Firstly - there are only 78 games supported* at the moment. So just be aware some of your faves might not be there yet.

Secondly - if you are running an Nvidia card you need to have x11-drivers/nvidia-drivers version 304.4 or higher installed. Steam will install but it won't get past login if you don't do this. You can solve this on Gentoo quite simply:

  • emerge x11-drivers/nvidia-drivers -avuDN

Installing QT Creator

In which I setup an IDE for my coding...

As with most of my Tinker posts to do with computers this is a guide to something I might need to do again in the future. You can probably find out how to do it online but I struggled with bits and am putting it here for my own and other's reference.

I am currently demonstrating a C++ lab at the University and it's good to be able to run the example code myself ahead of time. Also I am continuing to teach myself C++ as part of Project Euler.

I have a GUI

So following my post earlier today I now have a working xorg.conf and KDE 4.8.3 is running smoothly. Turns out there is an easy to use utility called nvidia-xconfig which I had overlooked and did the job perfectly. Also importantly I now have Chromium (Chrome for Linux if you didn't know) installed :) Time to start tinkering!

I've provided my xorg.conf here in-case it is useful to anyone. This works with a Nvidia GTS 450 linked by HDMI to a Panasonic 42" TX-P42U30B Plasma TV:

# nvidia-xconfig: X configuration file generated by nvidia-xconfig

# nvidia-xconfig: version 295.71 ( Thu Aug 2 20:28:32 PDT 2012

Section "ServerLayout" Identifier "Layout0" Screen 0 "Screen0" 0 0 InputDevice "Mouse0" "CorePointer" InputDevice "Keyboard0" "CoreKeyboard" EndSection

Section "Module" Load "glx" EndSection

Section "InputDevice" # generated from data in "/etc/conf.d/gpm" Identifier "Mouse0" Driver "mouse" Option "Protocol" Option "Device" "/dev/input/mice" Option "Emulate3Buttons" "no" Option "ZAxisMapping" "4 5" EndSection

Section "InputDevice" Identifier "Keyboard0" Driver "kbd" EndSection

Section "Modes" Identifier "Modes0" ModeLine "1920x1080@60" 182.28 1920 1952 2640 2672 1080 1102 1113 1135 EndSection

Section "Monitor" Identifier "Monitor0" VendorName "Unkown" ModelName "Unknown" UseModes "Modes0" HorizSync 28.0 - 33.0 VertRefresh 43.0 - 72.0 EndSection

Section "Device" Identifier "GTS450" Driver "nvidia" VendorName "NVIDIA Corporation" EndSection Section "Screen" Identifier "Screen0" Device "GTS450" Monitor "Monitor0" DefaultDepth 24 Option "ConnectedMonitor" "DEP-0" Option "DPMS" "false" SubSection "Display" Depth 24 EndSubSection EndSection

Tom out!

Gentoo 64-bit

So guess what I was up to last night - yes that's right, installing Gentoo.

This was my first time installing Gentoo on 64-bit architecture - the important specs are below:

  • Intel Core i7 2600k Processor (Sandy Bridge - important later)
  • 8 GB DDR3 RAM
  • Asus P8Z68-V PRO/GEN3 Motherboard
  • 250 GB HDD (well 250 GB partition out of the 4 TB in my machine)
  • Nvidia GeForce GTS 450 GPU
  • Blu-Ray recorder drive

Also worth noting that this is a dual boot with Windows 7.

[WARNING - If you're not interested in Linux or computer geekery I expect you will find the rest of this post boring]

I followed the Gentoo documentation found here: I will be noting any differences between that guide and my install here.

Choosing the Right Installation Medium

I downloaded the LiveCD and used that as my initial Linux environment for installing from.

Configuring your Network

All done through DHCP.

Preparing the Disks

I used the standard layout of boot, swap and root partitions but on /dev/sdb2 to /dev/sdb4 because of my dual booting. I set my swap partition to 20 GB following advice I found online. Then annoyingly the LiveCD made me reboot in order to write the changes. The I used the standard filesystems.

Installing the Gentoo Installation Files

The -march option in CFLAGS needs to be native or corei7-avx because of the Sandy Bridge architecture. I used MAKEOPTS="-j5" as it's a quad core processor.

Installing the Gentoo Base System

I selected the default amd64 profile. I set up my USE flags with KDE in mind so -gnome and -gtk were used. I also added the bluray flag.

Configuring the Kernel

I mostly followed the guide but later I had to come back and recompile without some Nvidia options:

Configuring your System

I always set my hostname to be the name of a famous fictional computer - this time I went for Ozymandias (

I set my locale to be en_GB.UTF-8.

Installing Necessary System Tools

I chose to get syslog-ng, vixie-cron, mlocate, dhcpcd and ppp.

Configuring the Bootloader

I used GRUB and followed the standard set-up except for a timeout of 10 seconds and replacing Windows XP with Windows 7. I also had to ensure to make the boot device hd1,1 and root=/dev/sdb4.

Finalizing your Gentoo Installation

I made my user with nearly all the groups (N.B. games doesn't work - is it depreciated?)

Where to go from here?

By the time I left for work this morning I had also emerged X-org and KDE 4.8.3 and had managed to get startx to not crash while going to a black screen. I'm going to have to work on my xorg.conf this evening and hopefully I'll get a working one running. This will be useful as Googling doesn't currently give a working one for my 42" TV and graphics card via HDMI. I hope people might find that useful :)

Tom out!