FlipCode is back

Kurt has tak­en steps to revive Flip­Code.

Flip­code was a place to dis­cuss gamedev + algo­rithms with a unique flair and an out­stand­ing audi­ence, some­thing IMHO gamedev.net nev­er matched. I, too, was a reg­u­lar vis­i­tor, poster, and also con­tributed the odd arti­cle and an IOTD. Ter­rain engines bor­der­ing on 100k polys with­out HW T&L will be for­ev­er in the past, but the spir­it will live on.

Branchless Matrix to Quaternion Conversion

(EDIT: This arti­cle is a more in-depth write­up of an algo­rithm that I devel­oped around 2005, and first post­ed to Mar­tin Bak­er’s Euclid­ean Space web­site. That time was the height of the Intel Net­Burst archi­tec­ture, which was noto­ri­ous for its deep pipeline and high branch mis­pre­dic­tion penal­ty. Hence the moti­va­tion to devel­op a branch-free matrix to quater­nion con­ver­sion rou­tine. What fol­lows is the com­plete deriva­tion and analy­sis of this idea.)

The orig­i­nal rou­tine to con­vert a matrix to a quater­nion was giv­en by Ken Shoe­make [1] and is very branchy. There is a way to elim­i­nate these branch­es and arrive at a com­plete­ly branch-free and high­ly par­al­leliz­able code. The trade off is the intro­duc­tion of 3 addi­tion­al square roots. Jump to the analy­sis sec­tion and the end of this arti­cle, or con­tin­ue fist with the math bits.


OpenGL 4.3

I just got the news about the OpenGL 4.3 spec, which was released today, and is avail­able at http://www.opengl.org/registry/. The spec doc­u­ment has been reor­ga­nized and cleared up con­sid­er­ably and is a lot eas­i­er to fol­low than the pre­vi­ous spec­i­fi­ca­tions. New fea­tures include (ordered by impor­tance for my projects):

  • Queries for inter­nal tex­ture for­mat parameters
  • Debug out­put callbacks
  • Com­pute shaders
  • Tex­ture views
  • and oth­ers

I’m cur­rent­ly on a project where com­pat­i­bil­i­ty and scaleabil­i­ty is prime, so the first two fea­tures are very wel­come as devel­op­ment aids to make the code run robust­ly on a vari­ety of plat­forms. Com­pute shaders and tex­ture views are of course cool, but require the newest hard­ware, so they are low­er in my list.

A nice touch by Nvidia to make to expose the new func­tion­al­i­ty as exten­sions on old­er hard­ware.