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Add some basic tests for easing functions#16675

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Add some basic tests for easing functions#16675
scottmcm wants to merge 1 commit intobevyengine:mainfrom
scottmcm:test-easing

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@scottmcm scottmcm commented Dec 6, 2024

Objective

Context for #16676

The release notes nerd-sniped me again. I was looking at the EaseFunction::Exponential* definition and wondering why that specific definition was chosen. And looking into it I noticed that it seemed wrong and there weren't any tests, so here are those tests -- which are failing as proof.

Solution

I don't know what the best answer is here, but I think having tests is at least a good start for a discussion.

Testing

These are tests 🙂

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scottmcm commented Dec 6, 2024

The tests fail:

---- curve::easing::tests::ease_functions_zero_to_one stdout ----
thread 'curve::easing::tests::ease_functions_zero_to_one' panicked at crates/bevy_math/src/curve/easing.rs:490:13:
EaseFunction.ExponentialIn(0) was 0.0009765625

see the mentioned issue for discussion.

@IQuick143 IQuick143 added C-Testing A change that impacts how we test Bevy or how users test their apps A-Math Fundamental domain-agnostic mathematical operations D-Straightforward Simple bug fixes and API improvements, docs, test and examples S-Needs-Review Needs reviewer attention (from anyone!) to move forward labels Dec 6, 2024
@BenjaminBrienen BenjaminBrienen added the S-Blocked This cannot move forward until something else changes label Dec 18, 2024
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Marking this as blocked on fixing #16676 with another PR, at which point this can be rebased and the tests should then pass.

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Pulled these tests into #16910, so closing this PR.

@scottmcm scottmcm closed this Dec 20, 2024
@scottmcm scottmcm deleted the test-easing branch December 20, 2024 07:31
github-merge-queue bot pushed a commit that referenced this pull request Dec 24, 2024
…6910)

And add a bunch of tests to show that all the monotonic easing functions
have roughly the expected shape.

# Objective

The `EaseFunction::Exponential*` variants aren't actually smooth as
currently implemented, because they jump by about 1‰ at the
start/end/both.

- Fixes #16676
- Subsumes #16675

## Solution

This PR slightly tweaks the shifting and scaling of all three variants
to ensure they hit (0, 0) and (1, 1) exactly while gradually
transitioning between them.

Graph demonstration of the new easing function definitions:
<https://www.desmos.com/calculator/qoc5raus2z>

![desmos-graph](https://github.com/user-attachments/assets/c87e9fe5-47d9-4407-9c94-80135eef5908)
(Yes, they look completely identical to the previous ones at that scale.
[Here's a zoomed-in
comparison](https://www.desmos.com/calculator/ken6nk89of) between the
old and the new if you prefer.)

The approach taken was to keep the core 2¹⁰ᵗ shape, but to [ask
WolframAlpha](https://www.wolframalpha.com/input?i=solve+over+the+reals%3A+pow%282%2C+10-A%29+-+pow%282%2C+-A%29%3D+1)
what scaling factor to use such that f(1)-f(0)=1, then shift the curve
down so that goes from zero to one instead of ¹/₁₀₂₃ to ¹⁰²⁴/₁₀₂₃.

## Testing

I've included in this PR a bunch of general tests for all monotonic
easing functions to ensure they hit (0, 0) to (1, 1), that the InOut
functions hit (½, ½), and that they have the expected convexity.

You can also see by inspection that the difference is small. The change
for `exponential_in` is from `exp2(10 * t - 10)` to `exp2(10 * t -
9.99859…) - 0.0009775171…`.

The problem for `exponential_in(0)` is also simple to see without a
calculator: 2⁻¹⁰ is obviously not zero, but with the new definition
`exp2(-LOG2_1023) - FRAC_1_1023` => `1/(exp2(LOG2_1023)) - FRAC_1_1023`
=> `FRAC_1_1023 - FRAC_1_1023` => `0`.


---

## Migration Guide

This release of bevy slightly tweaked the definitions of
`EaseFunction::ExponentialIn`, `EaseFunction::ExponentialOut`, and
`EaseFunction::ExponentialInOut`. The previous definitions had small
discontinuities, while the new ones are slightly rescaled to be
continuous. For the output values that changed, that change was less
than 0.001, so visually you might not even notice the difference.

However, if you depended on them for determinism, you'll need to define
your own curves with the previous definitions.

---------

Co-authored-by: IQuick 143 <IQuick143cz@gmail.com>
pcwalton pushed a commit to pcwalton/bevy that referenced this pull request Dec 25, 2024
…vyengine#16910)

And add a bunch of tests to show that all the monotonic easing functions
have roughly the expected shape.

# Objective

The `EaseFunction::Exponential*` variants aren't actually smooth as
currently implemented, because they jump by about 1‰ at the
start/end/both.

- Fixes bevyengine#16676
- Subsumes bevyengine#16675

## Solution

This PR slightly tweaks the shifting and scaling of all three variants
to ensure they hit (0, 0) and (1, 1) exactly while gradually
transitioning between them.

Graph demonstration of the new easing function definitions:
<https://www.desmos.com/calculator/qoc5raus2z>

![desmos-graph](https://github.com/user-attachments/assets/c87e9fe5-47d9-4407-9c94-80135eef5908)
(Yes, they look completely identical to the previous ones at that scale.
[Here's a zoomed-in
comparison](https://www.desmos.com/calculator/ken6nk89of) between the
old and the new if you prefer.)

The approach taken was to keep the core 2¹⁰ᵗ shape, but to [ask
WolframAlpha](https://www.wolframalpha.com/input?i=solve+over+the+reals%3A+pow%282%2C+10-A%29+-+pow%282%2C+-A%29%3D+1)
what scaling factor to use such that f(1)-f(0)=1, then shift the curve
down so that goes from zero to one instead of ¹/₁₀₂₃ to ¹⁰²⁴/₁₀₂₃.

## Testing

I've included in this PR a bunch of general tests for all monotonic
easing functions to ensure they hit (0, 0) to (1, 1), that the InOut
functions hit (½, ½), and that they have the expected convexity.

You can also see by inspection that the difference is small. The change
for `exponential_in` is from `exp2(10 * t - 10)` to `exp2(10 * t -
9.99859…) - 0.0009775171…`.

The problem for `exponential_in(0)` is also simple to see without a
calculator: 2⁻¹⁰ is obviously not zero, but with the new definition
`exp2(-LOG2_1023) - FRAC_1_1023` => `1/(exp2(LOG2_1023)) - FRAC_1_1023`
=> `FRAC_1_1023 - FRAC_1_1023` => `0`.


---

## Migration Guide

This release of bevy slightly tweaked the definitions of
`EaseFunction::ExponentialIn`, `EaseFunction::ExponentialOut`, and
`EaseFunction::ExponentialInOut`. The previous definitions had small
discontinuities, while the new ones are slightly rescaled to be
continuous. For the output values that changed, that change was less
than 0.001, so visually you might not even notice the difference.

However, if you depended on them for determinism, you'll need to define
your own curves with the previous definitions.

---------

Co-authored-by: IQuick 143 <IQuick143cz@gmail.com>
ecoskey pushed a commit to ecoskey/bevy that referenced this pull request Jan 6, 2025
…vyengine#16910)

And add a bunch of tests to show that all the monotonic easing functions
have roughly the expected shape.

# Objective

The `EaseFunction::Exponential*` variants aren't actually smooth as
currently implemented, because they jump by about 1‰ at the
start/end/both.

- Fixes bevyengine#16676
- Subsumes bevyengine#16675

## Solution

This PR slightly tweaks the shifting and scaling of all three variants
to ensure they hit (0, 0) and (1, 1) exactly while gradually
transitioning between them.

Graph demonstration of the new easing function definitions:
<https://www.desmos.com/calculator/qoc5raus2z>

![desmos-graph](https://github.com/user-attachments/assets/c87e9fe5-47d9-4407-9c94-80135eef5908)
(Yes, they look completely identical to the previous ones at that scale.
[Here's a zoomed-in
comparison](https://www.desmos.com/calculator/ken6nk89of) between the
old and the new if you prefer.)

The approach taken was to keep the core 2¹⁰ᵗ shape, but to [ask
WolframAlpha](https://www.wolframalpha.com/input?i=solve+over+the+reals%3A+pow%282%2C+10-A%29+-+pow%282%2C+-A%29%3D+1)
what scaling factor to use such that f(1)-f(0)=1, then shift the curve
down so that goes from zero to one instead of ¹/₁₀₂₃ to ¹⁰²⁴/₁₀₂₃.

## Testing

I've included in this PR a bunch of general tests for all monotonic
easing functions to ensure they hit (0, 0) to (1, 1), that the InOut
functions hit (½, ½), and that they have the expected convexity.

You can also see by inspection that the difference is small. The change
for `exponential_in` is from `exp2(10 * t - 10)` to `exp2(10 * t -
9.99859…) - 0.0009775171…`.

The problem for `exponential_in(0)` is also simple to see without a
calculator: 2⁻¹⁰ is obviously not zero, but with the new definition
`exp2(-LOG2_1023) - FRAC_1_1023` => `1/(exp2(LOG2_1023)) - FRAC_1_1023`
=> `FRAC_1_1023 - FRAC_1_1023` => `0`.


---

## Migration Guide

This release of bevy slightly tweaked the definitions of
`EaseFunction::ExponentialIn`, `EaseFunction::ExponentialOut`, and
`EaseFunction::ExponentialInOut`. The previous definitions had small
discontinuities, while the new ones are slightly rescaled to be
continuous. For the output values that changed, that change was less
than 0.001, so visually you might not even notice the difference.

However, if you depended on them for determinism, you'll need to define
your own curves with the previous definitions.

---------

Co-authored-by: IQuick 143 <IQuick143cz@gmail.com>
mrchantey pushed a commit to mrchantey/bevy that referenced this pull request Feb 4, 2025
…vyengine#16910)

And add a bunch of tests to show that all the monotonic easing functions
have roughly the expected shape.

# Objective

The `EaseFunction::Exponential*` variants aren't actually smooth as
currently implemented, because they jump by about 1‰ at the
start/end/both.

- Fixes bevyengine#16676
- Subsumes bevyengine#16675

## Solution

This PR slightly tweaks the shifting and scaling of all three variants
to ensure they hit (0, 0) and (1, 1) exactly while gradually
transitioning between them.

Graph demonstration of the new easing function definitions:
<https://www.desmos.com/calculator/qoc5raus2z>

![desmos-graph](https://github.com/user-attachments/assets/c87e9fe5-47d9-4407-9c94-80135eef5908)
(Yes, they look completely identical to the previous ones at that scale.
[Here's a zoomed-in
comparison](https://www.desmos.com/calculator/ken6nk89of) between the
old and the new if you prefer.)

The approach taken was to keep the core 2¹⁰ᵗ shape, but to [ask
WolframAlpha](https://www.wolframalpha.com/input?i=solve+over+the+reals%3A+pow%282%2C+10-A%29+-+pow%282%2C+-A%29%3D+1)
what scaling factor to use such that f(1)-f(0)=1, then shift the curve
down so that goes from zero to one instead of ¹/₁₀₂₃ to ¹⁰²⁴/₁₀₂₃.

## Testing

I've included in this PR a bunch of general tests for all monotonic
easing functions to ensure they hit (0, 0) to (1, 1), that the InOut
functions hit (½, ½), and that they have the expected convexity.

You can also see by inspection that the difference is small. The change
for `exponential_in` is from `exp2(10 * t - 10)` to `exp2(10 * t -
9.99859…) - 0.0009775171…`.

The problem for `exponential_in(0)` is also simple to see without a
calculator: 2⁻¹⁰ is obviously not zero, but with the new definition
`exp2(-LOG2_1023) - FRAC_1_1023` => `1/(exp2(LOG2_1023)) - FRAC_1_1023`
=> `FRAC_1_1023 - FRAC_1_1023` => `0`.


---

## Migration Guide

This release of bevy slightly tweaked the definitions of
`EaseFunction::ExponentialIn`, `EaseFunction::ExponentialOut`, and
`EaseFunction::ExponentialInOut`. The previous definitions had small
discontinuities, while the new ones are slightly rescaled to be
continuous. For the output values that changed, that change was less
than 0.001, so visually you might not even notice the difference.

However, if you depended on them for determinism, you'll need to define
your own curves with the previous definitions.

---------

Co-authored-by: IQuick 143 <IQuick143cz@gmail.com>
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A-Math Fundamental domain-agnostic mathematical operations C-Testing A change that impacts how we test Bevy or how users test their apps D-Straightforward Simple bug fixes and API improvements, docs, test and examples S-Blocked This cannot move forward until something else changes S-Needs-Review Needs reviewer attention (from anyone!) to move forward

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