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Freya Holmér Profile picture
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Nov 25 • 5 tweets • 1 min read
fuck it, I did the math, swizzle your quaternions (w,x,y,z) why not

(-x, w, -z, y) is 180° around X
(-y, z, w, -x) is 180° around Y
(-z, -y, x, w) is 180° around Z
btw those are "local space"/intrinsic rotations, here are the "world space"/extrinsic rotations:

(-x, w, z, -y) is 180° around world X
(-y, -z, w, x) is 180° around world Y
(-z, y, -x, w) is 180° around world Z
also I might be wrong bc this is completely untested so don't trust me
I have now tested it and it works! (except I got extrinsic/intrinsic backwards)
ok there we go

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More from @FreyaHolmer

Freya Holmér Profile picture
Nov 25
my big takeaway studying quaternions a little closer as of late, is that interpreting them as a 4D object is a red herring
they make a lot more sense when you think of them as a special encoding of an angle-axis model with special multiplication rules, or, as rotors in the framework of geometric algebra
treating the xyzw components as the same type of element in the same type of space just isn't helpful (to me), because they operate with completely different rules

w is just a regular ol number on the number line

x, y and z are very much not
Read 5 tweets
Freya Holmér Profile picture
Oct 31
blender first impressions thread! (as a maya user)

1. it's super hard to see what the heck is going on when you parent objects using the default parenting method

child objects have some sort of hidden (??) offset based on their relation when parenting
this offset seems to be completely hidden in the UI

basically, both transform and delta transform can be at (0,0,0), and yet the object is neither at (0,0,0) world space, nor at the parent position

what is that offset? *who knows* I couldn't figure it out and neither could chat
basically, this very specific option is the only reasonable parenting method to me

it makes me super uncomfortable that there even is an option to parent objects and then not being able edit or even see their relationship to each other ;-; ??
Read 6 tweets
Freya Holmér Profile picture
Oct 28
the four most common 3D rotation representations
this type of axis-angle form is also know as a rotation vector, where the magnitude represents the angle, and the axis represents the axis to rotate around

sometimes the axis and the angle are stored separately in 4 numbers (x,y,z,angle)
rotation matrices are pretty beefy memory-wise, but because they have all three axes directly stored in 9 numbers, transformations are very easy and fast. they also composite and combine well! (though not quickly)
Read 7 tweets
Freya Holmér Profile picture
Oct 27
I wish I felt more comfortable responding "I don't know" to support questions
I feel this pressure to be some sort of all knowing deity who has to either already know the answer or figure out every problem every person has on every platform
anyway
Read 4 tweets
Freya Holmér Profile picture
Aug 14
okay haha holy buckets

Material.SetInt() allocates a *huge* amount of memory, and yet it isn't marked as deprecated (as of 2021.2)

its inline doc says it's deprecated, but it doesn't have the obsolete attribute 💀

and why was a function added, instead of fixing the original?
it looks like it's related to a change in 2021.1, where unity got support for proper integer shader properties

prior to this, they were floats under the hood, and somehow, this means, allocations, somewhere, along the way
wait now I'm getting it with SetInteger too ;-;

why is it allocating help
Read 4 tweets
Freya Holmér Profile picture
Jun 23
I have no idea how to tell if I'm learning anything when doing this ,_,
it's hard to tell how the ribcage/hip boxes relate to, almost anything. like, I feel like the ribcage box should align with the spine/ribcage back, but the top/bottom faces don't really represent anything when it comes to their angles?

pose refs from deviantart.com/lalunatique/ar…
like I guess it's meant to mostly hint at the orientation/approximate size, but, if that's all it is, then I'd rather just make, a cross at the back of the spine or something, because the boxes to me feel like they're trying to be more than that
Read 4 tweets

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