Collision is weird

BringUpYourPost

I heard that scratch's collision is not deterministic I thought that was because of screen sizes, I know that is true. but i think there are other causes to this undeterminism. Case in point: GOISE TASING cannot store the exact inputs because the same inputs leads to different state with same screen size.

Last edited by BringUpYourPost (May 9, 2024 19:24:43)

Paddle2See

I have no idea what you are talking about here - but it doesn't seem to be a good fit for “Questions About Scratch”.

“Advanced Topics” maybe?

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BringUpYourPost

Paddle2See wrote:
I have no idea what you are talking about here - but it doesn't seem to be a good fit for “Questions About Scratch”.

“Advanced Topics” maybe?

Maybe.

I still wonder why collision is undeterministic. (even if you ignore the existance of image pixelation due to screen size)

Why is this?

undeterministic

Here are the revelant source code: https://github.com/scratchfoundation/scratch-vm/blob/develop/src/blocks/scratch3_sensing.js

ninjaMAR

undeterministic wrote:
(#4)
Here are the revelant source code: https://github.com/scratchfoundation/scratch-vm/blob/develop/src/blocks/scratch3_sensing.js

It is line 171. However, it is just delegates util.target.isTouchingObject. I believe util is the sprite the script is running on.

username checks out

Last edited by ninjaMAR (May 9, 2024 02:30:45)

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undeterministic

ninjaMAR wrote:
undeterministic wrote:
(#4)
Here are the revelant source code: https://github.com/scratchfoundation/scratch-vm/blob/develop/src/blocks/scratch3_sensing.js
It is line 171. However, it is just delegates util.target.isTouchingObject. I believe util is the sprite the script is running on.

username checks out

https://github.com/scratchfoundation/scratch-vm/blob/develop/src/sprites/rendered-target.js#L743

undeterministic

I noticed rendered target extends the class target, which extends EventEmitter, but i can't find it.

CST1229

util is not the sprite itself, it's an instance of BlockUtility: https://github.com/scratchfoundation/scratch-vm/blob/develop/src/engine/block-utility.js

undeterministic wrote:
(#7)
I noticed rendered target extends the class target, which extends EventEmitter, but i can't find it.

RenderedTarget: https://github.com/scratchfoundation/scratch-vm/blob/develop/src/sprites/rendered-target.js
Target: https://github.com/scratchfoundation/scratch-vm/blob/develop/src/engine/target.js
EventEmitter is a built-in node.js class, it is not in the scratch-vm code.

The actual touching code is in scratch-render: https://github.com/scratchfoundation/scratch-render/blob/af4b81021842eb792fadde328018c1953022eef3/src/RenderWebGL.js#L961-L1002
It references Drawable.isTouching: https://github.com/scratchfoundation/scratch-render/blob/af4b81021842eb792fadde328018c1953022eef3/src/Drawable.js#L487-L505
Which then eventually references Silhouette.isTouching[Nearest/Linear]: https://github.com/scratchfoundation/scratch-render/blob/af4b81021842eb792fadde328018c1953022eef3/src/Silhouette.js#L219-L242

Silhouette is a class that basically stores the sprite image for collision detection. It gets updated here for vector images: https://github.com/scratchfoundation/scratch-render/blob/af4b81021842eb792fadde328018c1953022eef3/src/SVGSkin.js#L142

Last edited by CST1229 (May 9, 2024 21:02:54)

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