Weird GLSLang Shader Error

Hunting a shader compilation error for about an hour before finally finding the problem: Something worth sharing.

Being used to the mostly useful GLSL shader error strings, here is what I was left with this time:The only clue: The error occurs in the fragment shader. Another weird thing about this error is, that it does not occur on all GPUs. For example it runs fine on my Nexus 7 but not on the Incredible S (Adreno200).

The shader performed the simple Blinn-Phong per-pixel lighting. The problem lied within one of my vec3 variables:

vec3 half = normalize(light + view);

By that time I was unaware that half is one of the reserved keyword declared in the GLSLang Specification for future use. Renaming that variable to something else allowed the shader to compile. Sometimes it’s that easy.

Installing stand-alone Google PlayStore

Due to recent demand, I had to figure out how to install the Google PlayStore on Android without all the other apps coming with the GApps package. Here is how to install the stand-alone PlayStore. Hint: Your device has to be rooted in order for it to work.

1. Download the GApps package corresponding to your ROM from http://wiki.rootzwiki.com/Google_Apps.
2. Open it and extract following files from the system/app folder within the zip: GoogleLoginService.apk, GoogleServicesFramework.apk, Phonesky.apk and, if existing, GmsCore.apk.
3. Copy these files to your Android device and move them with any root-capable file browser to: /system/app
4. Change permissions of the files to 644 (same as all the other apks)
5. Reboot

After that, you should see the PlayStore app on the device and it should work just fine. This was tested with a custom CyanogenMod build running Android 4.1.2 on an HTC Incredible S.

Install Android x86 on your computer

If you want to try out Android on your laptop or computer you can download the most recent version from the Android-x86 Download Section. As the time of writing, this would be an Android 4.3 test version.
You can now burn this ISO-Image to a CD or put it on a bootable USB device. However, you can also extract the content of the image to an arbitrary folder on your local hard drive and boot from there with the help of Grub2. I extracted the contents of the image to the folder:

/android-4.3

Append the following entries to the Grub2 configuration file in /etc/grub.d/40_custom while replacing #X with the number of the hard drive (starting at 0) and #Y with the number of the partition (starting at 1). Example: sda1=(hd0,1) or sdb2=(hd1,2).

menuentry "Android 4.3 Live" {
	set root=(hd#X,#Y)
	linux /android-4.3/kernel quiet root=/dev/ram0 androidboot.hardware=android_x86 acpi_sleep=s3_bios,s3_mode SRC=/android-4.3
	initrd /android-4.3/initrd.img
}

menuentry "Android 4.3 Install" {
	set root=(hd#X,#Y)
	linux /android-4.3/kernel quiet root=/dev/ram0 androidboot.hardware=android_x86 acpi_sleep=s3_bios,s3_mode SRC=/android-4.3 INSTALL=1
	initrd /android-4.3/initrd.img
}

Update Grub with sudo update-grub and reboot. Choose from the new menu entries in Grub for either trying it out by selecting the Live entry or installing it by selecting the Install entry. Be reminded, that anything you do in the Live system won’t be permanent.

Installing Android is a fast and easy process with the text based installer. After you have successfully installed it, you have to add a new menu entry in Grub again to boot into your newly installed Android. Check the partition you installed Android on: there should be a single folder containing the files of the Android system. We need the name of the folder for the new Grub entry. In my case, this folder is named android-4.3-test. So the new entry goes like this:

menuentry "Android 4.3" {
	set root=(hd#X,#Y)
	linux /android-4.3-test/kernel quiet root=/dev/ram0 androidboot.hardware=android_x86 acpi_sleep=s3_bios,s3_mode SRC=/android-4.3-test
	initrd /android-4.3-test/initrd.img
}

Don’t forget to replace #X and #Y again with the correct hard drive / partition you installed Android on and correct the folder name matching your own (if different). Now update Grub again and reboot into your Android installation. Have fun playing around!

Boot ISO-Image from local hard drive with Grub2

Want to run a Live-CD or install an new operating system? If you’re running out of dvd’s to burn and don’t have a usb drive around, booting a downloaded ISO-Image directly from the local hard drive is probably what you want to do. In this example, I will demonstrate how to boot into Linux Mint and Manjaro. You will need the bootloader Grub2 for it to work.

Place the ISO-Image in a folder on your hard drive. Any partition and folder can be used as long as it can be mounted by Grub. For the ease of use, I put the image directly in the root directory of the running linux system. Use administrator rights to gain write permission to root (sudo nautilus or sudo nemo).

/linuxmint-16-cinnamon-dvd-64bit.iso
/manjaro-xfce-0.8.8-x86_64.iso

Now add the new boot menu entries to the Grub2 configuration file. Open following file with write permissions:

/etc/grub.d/40_custom

Append the following lines to the file while replacing #X with the number of the hard drive (starting at 0) and #Y with the number of the partition (starting at 1). Example: sda1=(hd0,1) or sdb2=(hd1,2). For Manjaro also replace the asterisks with the disk device name, e.g. sda1 or sdb2.

menuentry "Linux Mint 16" {
  set isofile="/linuxmint-16-cinnamon-dvd-64bit.iso"
  loopback loop (hd#X,#Y)$isofile
  linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=$isofile noprompt noeject
  initrd (loop)/casper/initrd.lz
}

menuentry "Manjaro 0.8.8" {
  set isofile="/manjaro-xfce-0.8.8-x86_64.iso"
  loopback loop (hd#X,#Y)$isofile
  linux (loop)/manjaro/boot/x86_64/manjaroiso img_dev=/dev/**** img_loop=$isofile misobasedir=manjaro misolabel=MJRO_086 nouveau.modeset=0 i915.modeset=1 radeon.modeset=0
  initrd (loop)/manjaro/boot/x86_64/manjaro.img
}

Update Grub by running the command:

sudo update-grub

Reboot and choose the new menu entry in Grub to boot the corresponding ISO-image.
If you boot into a Live-CD and you want to install the OS, simply run the following code to unmount the iso device before starting the installer.

sudo umount -l -r -f /isodevice

---

Hint: If the booting of the Manjaro image reports an error and you are stuck in a bash, type in these commands to bypass the problem:

mount -o loop /img_dev/manjaro-xfce-0.8.8-x86_64.iso /bootmnt/
exit

Enjoy!