Awesome tools for Windows users

I moved back to Windows on my home computer a few months back. There are a few amazing free tools I've found since then that have been making my life better and I thought they deserved a shout-out. They are:

SumatraPDF
A fantastic PDF reader. Does everything I want and nothing I don't.

RapidEE
A sane way to edit environment variables. The simple joy of just being able to resize the window is... incredible.

7-Zip
The best tool for dealing with compressed files on windows, bar none.

GPU-Z
A really handy way to see details about your GPU(s).

XnView
An amazingly good image viewer, which can also do bulk file format conversions.

If you haven't already got these... go get them!

Comments

Octree node identifiers

Let's say we have an octree and we want to come up with a unique integer that can identify any node in the tree - including interior nodes, not just leaf nodes. Let's also say that the octree has a maximum depth no greater than 9 levels, i.e. the level containing the leaf nodes divides space into 512 parts along each axis.

The encoding The morton encoding of a node's i,j,k coordinates within the tree lets us identify a node uniquely if we already know it's depth. Without knowing the depth, there's no way to differentiate between cells at different depths in the tree. For example, the node at depth 1 with coords 0,0,0 has exactly the same morton encoding as the node at depth 2 with coords 0,0,0.

We can fix this by appending the depth of the node to the morton encoding. If we have an octree of depth 9 then we need up to 27 bits for the morton encoding and 4 bits for the depth, which still fits nicely into a 32-bit integer. We'll shift the morton code up so that i…

How to outperform std::vector in 1 easy step

Everyone who's familiar with C++ knows that you should avoid resizing a std::vector inside a loop wherever possible. The reasoning's pretty obvious: the memory allocated for the vector doubles in size each time it fills up and that doubling is a costly operation. Have you ever wondered why it's so costly though?

It's tempting to assume that because implementations of the STL have been around for so long that they must be pretty efficient. It turns out that's a bad assumption because the problem, in this case, is the standard itself: specifically, the allocator interface.

The allocator interface provides two methods that obtain and release memory:

allocate allocates uninitialized storage
(public member function)deallocate deallocates storage
(public member function)

(taken from this page).

What's missing is away of growing an existing memory allocation in place. In C this is provided by the realloc function, but there's no equivalent in the std::allocator interfa…

Faster morton codes with compiler intrinsics

Today I learned that newer Intel processors have an instruction which is tailor-made for generating morton codes: the PDEP instruction. There's an instruction for the inverse as well, PEXT.

These exist in 32- and 64-bit versions and you can use them directly from C or C++ code via compiler intrinsics: _pdep_u32/u64 and _pext_u32/u64. Miraculously, both the Visual C++ and GCC versions of the intrinsics have the same names. You'll need an Intel Haswell processor or newer to be able to take advantage of them though.

Docs for the instructions:

Intel's docs GCC docs Visual C++ docs
This page has a great write up of older techniques for generating morton codes:

Jeroen Baert's blog ...but the real gold is hidden at the bottom of that page in a comment from Julien Bilalte, which is what clued me in to the existence of these instructions.
Update: there's some useful info on Wikipedia about these intructions too.

Coder Vil

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