58 lines
1.7 KiB
Lua
58 lines
1.7 KiB
Lua
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--!strict
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-- A simple fixed step system scheduler
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-- Fixed updates can happen multiple times per frame
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-- Variable updates will happen after all fixed updates complete
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local FIXED_DELTA = (1 / 60)
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local MAXIMUM_DELTA = (1 / 5)
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export type System = {
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--> variable delta_time update, used for rendering
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--> blend used for interpolation of simulation state
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update: ((delta_time: number, blend: number) -> ())?,
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--> fixed delta_time update, used for simulation
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fixed_update: ((delta_time: number, frame: number) -> ())?,
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}
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local function create(systems: {System}): (number) -> ()
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local frame = 0
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local accumulator = 0
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return function(delta_time: number)
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delta_time = math.min(delta_time, MAXIMUM_DELTA)
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accumulator += delta_time
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local steps = 0
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local previous_frame = frame
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if (accumulator > 0) then
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--> typically done with a while accumulator >= fixed_rate but this way is 35x faster
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steps = accumulator // FIXED_DELTA
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frame += steps
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accumulator -= (steps * FIXED_DELTA)
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end
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for step = 1, steps do
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local step_frame = previous_frame + step
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for _, system in systems do
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if system.fixed_update == nil then
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continue
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end
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system.fixed_update(FIXED_DELTA, step_frame)
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end
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end
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local blend = accumulator / FIXED_DELTA
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for _, system in systems do
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if system.update == nil then
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continue
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end
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system.update(delta_time, blend)
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end
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end
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end
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return create
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