mirror of
https://github.com/open-goal/jak-project
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water
110 lines
2.6 KiB
Scheme
110 lines
2.6 KiB
Scheme
;-*-Scheme-*-
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(in-package goal)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;; float utility
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(defun truncate ((x float))
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"Truncate a floating point number by converting to an integer and back."
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(declare (inline))
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(the float (the integer x))
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)
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(defun integral? ((x float))
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"Is a floatint point number an exact integer?"
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(= (truncate x) x)
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)
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(defun fractional-part ((x float))
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"Get the fractional part of a floating point number"
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(- x (truncate x))
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)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;; bitfield types
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(deftype rgba (uint32)
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((r uint8)
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(g uint8)
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(b uint8)
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(a uint8)
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)
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)
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;; todo xyzw, xyzwh
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;; math utils and tricks
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(defun log2 ((x integer))
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"Straight out of Bit Twiddling Hacks graphics.stanford.edu"
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(- (sar (the-as integer (the float x)) 23) 127)
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)
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(defun seek ((x float) (target float) (diff float))
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"Move x toward target by at most diff, with floats"
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(let ((err (- target x)))
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;; if we can get there all at once
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(if (<= (fabs err) diff)
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(return-from #f target)
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)
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(if (>= err 0)
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(+ x diff)
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(- x diff)
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)
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)
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)
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(defun lerp ((minimum float) (maximum float) (amount float))
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"Interpolate between minimum and maximum. The output is not clamped."
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(+ minimum (* amount (- maximum minimum)))
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)
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(defun lerp-scale ((min-out float) (max-out float)
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(in float) (min-in float) (max-in float))
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"Interpolate from [min-in, max-in] to [min-out, max-out].
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If the output is out of range, it will be clamped.
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This is not a great implementation."
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(let ((scale (fmax 0.0 (fmin 1.0 (/ (- in min-in) (- max-in min-in))))))
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(+ (* (- 1 scale) min-out)
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(* scale max-out)
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)
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)
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)
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(defun lerp-clamp ((minimum float) (maximum float) (amount float))
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"Interpolate between minimum and maximum. Clamp output.
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For some reason, the interpolate here is done in a less efficient way than lerp."
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(if (<= amount 0.0)
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(return-from #f minimum)
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)
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(if (>= amount 1.0)
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(return-from #f maximum)
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)
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;; lerp computes this part, but more efficiently
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(+ (* (- 1 amount) minimum)
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(* amount maximum)
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)
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)
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(defun seekl ((x integer) (target integer) (diff integer))
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"Move x toward a target by at most diff, with integers"
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(let ((err (- target x)))
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(if (< (abs err) diff)
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(return-from #f target)
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)
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(if (>= err 0)
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(+ x diff)
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(- x diff)
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)
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)
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) |