Books for Game Developers

Post by xeonmc » Fri, Sep 15, 2023, 10:39 PM UTC

eestrada wrote: post #24

jessetemp wrote: post #4

Circa 90s and early 2000s. I like how there's a whole book on quaternions. I've never understood them and I'm convinced every definition I've read was written by someone who also didn't understand them. I might try to find a copy if I ever dabble in 3d again Edit: To clarify, I understand the need for quaternions (to avoid gimbal lock), just not how to use them manually. Euler angles are simple enough, I can change w…

My (poor) understanding of quaternions is they are like a vector with a rotation angle around the axis of the vector. This is probably incorrect on many levels. But it was a simple enough explanation that it made sense to my brain why this would work better than simple SRT transform parameters for avoiding gimbal lock. It's been several years since I needed to deal with 3D transformations of any sort, so I'm a bit ru…

    “angle”  [quaternion]
    “45deg”  [sqrt2 , sqrt2]

    Quaternion = sqrt( exp(axis_angle) )
               =       exp(axis_angle/2)
               = cos(angle/2) + axis*sin(angle/2)

    (lw,lx,ly,lz)*(rw,rx,ry,rz) = (w,x,y,z) 
    where
      w = ww-xx-yy-zz 
      x = wx+xw+yz-zy 
      y = wy+yw+zx-xz 
      z = wz+zw+xy-yx 
      where
        ww,wx,wy,wz = lw*rw,lw*rx,lw*ry,lw*rz 
        xw,xx,xy,xz = lx*rw,lx*rx,lx*ry,lx*rz
        yw,yx,yy,yz = ly*rw,ly*rx,ly*ry,ly*rz
        zw,zx,zy,zz = lz*rw,lz*rx,lz*ry,lz*rz

Post by pclmulqdq » Fri, Sep 15, 2023, 11:27 PM UTC

Animats wrote: post #22

alex_lav wrote: post #8

Earlier quoted context omitted.

Sounds like they're the gamedev equivalent of a Monad? Which I only vaguely understand as a result of a poster on this forum's "Everyone explains it wrong" style post. Hoping you get a similar response with this.

Quaternions tend to be over-complicated. Basic concept, 1 dimensional form: you want to represent a direction in a 2D plane. You can use one number, a heading angle, but at some point you reach a full circle and the number has to wrap. This creates annoying special cases. So another approach is to use a 2D vector, a point on a circle. Those are usually normalized so that x^2 + y^2 = 1. No angle is "special". You can…

Post by xeonmc » Sat, Sep 16, 2023, 12:23 AM UTC

i_c_b wrote: post #14

Wow. This post gave me emotional whiplash. I opened the collection of links, which is quite good if a bit old. But then I had a subconscious mental itch, and thought, wait... where had I heard the name mrelusive before? That sounds _really_ familiar. And then I remembered - oh, right, mrelusive, JP-what's-his-name. I've read a huge amount of his code. When I was working on Quake4 as a game programmer and technical de…

Post by andersa » Sat, Sep 16, 2023, 12:43 AM UTC

pclmulqdq wrote: post #33

Animats wrote: post #22

Earlier quoted context omitted.

Quaternions tend to be over-complicated. Basic concept, 1 dimensional form: you want to represent a direction in a 2D plane. You can use one number, a heading angle, but at some point you reach a full circle and the number has to wrap. This creates annoying special cases. So another approach is to use a 2D vector, a point on a circle. Those are usually normalized so that x^2 + y^2 = 1. No angle is "special". You can…

I am going to be the HN pedant here, and for that I apologize. Quaternions don't specifically need to be unit vectors or points on a 4-D hypersphere. They are any number with 3 imaginary parts and 1 real part. Being a unit operator is a property of a rotation (this holds true even if you aren't using quaternions or if you extend to n-dimensional rotations), not a property of quaternions.

Post by musicale » Sat, Sep 16, 2023, 1:26 AM UTC

mentos wrote: post #17

i_c_b wrote: post #14

Wow. This post gave me emotional whiplash. I opened the collection of links, which is quite good if a bit old. But then I had a subconscious mental itch, and thought, wait... where had I heard the name mrelusive before? That sounds _really_ familiar. And then I remembered - oh, right, mrelusive, JP-what's-his-name. I've read a huge amount of his code. When I was working on Quake4 as a game programmer and technical de…

My biggest takeaway from my time programming in Objective-C was not being afraid to name functions and variables more verbosely. Curious to hear what aspects of Objective-C you feel influenced id?