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A comment on Solving differential equations on a 6502 with Woz's floating point code. Parent comment

Re:Solving differential equations on a 6502 with Woz's float... by markrages on Thursday August 01, 2019 @10:52PM (#20590378)
Were you using a CORDIC algorithm? Bit shifts and adds, no multiplies required.
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Re:Solving differential equations on a 6502 with Woz's float... by djmips on Thursday August 01, 2019 @11:19PM (#20590476)
You don't need CORDIC to draw a circle. BTW, I implemented a CORDIC routine in 6502. It would really benefit from a barrel shifter which the 6502 does not have. https://atariage.com/forums/blogs/entry/3385-atan2-in-6502/

In gist form https://gist.github.com/djmips/29a8fa9099bf92b31a7259da65915...

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Re:Solving differential equations on a 6502 with Woz's float... by pascal_cuoq on Friday August 02, 2019 @06:39AM (#20591917)
Using a CORDIC algorithm would mean having many iterations to compute trigonometric functions for each drawn point (well, for each 8 points considering the symmetries). A variant of the Bresenham line algorithm for circles lets you draw a circle using only a few operations per 8 points (and the operations are also limited to add and shift):

https://en.wikipedia.org/wiki/Midpoint_circle_algorithm

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Re:Solving differential equations on a 6502 with Woz's float... by keithnz on Thursday August 01, 2019 @11:11PM (#20590445)
no, I had hardcoded lookup tables. I was a teen with no real way to find out information about anything and just applied my high school math to the problem :)
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