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Undiscussed Horrific Abuse, One Victim of Many gmkarl at gmail.com
Thu Jun 23 05:34:20 PDT 2022

i'm confused around the screen matrix
can i do this with a 2x2 matrix? how do i do it?

it's not a 2d transformation matrix if it's 2x2. that would be 3x3.

when i think of the 2x2 matrix, i imagine it applying to an equation:
the first column multiplies, the second adds. then i can put input
things in.

maybe it isn't matrix multiplication i'm thinking of. maybe it's just
normal broadcast multiplication.

or something?

i think i would need the points expressed as a 2x2 matrix themselves,
for this to work. with 1s underneth them to add.


what way makes sense to do here?

- i have two data items in the form of a vector [x,y,w,1]
- i care only about x and y
- i want to perform a linear transformation to both x and y
- the vectors i have are in a matrix stacked [v1,v2,v3,v4]

so what makes sense here?
we could do it in two operations, multiply and add

there's likely a way to do this with a matrix
there are likely other operations that would do multiply+add in numpy,
but they may be less intuitive to read in the context of graphics

so maybe i'll make a 3x3 matrix instead of 2x2. that might make sense. or a 3x2.

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