6 ms·

Super Mario 64's invisible walls explained [video]

136 points by mbStavola 3y ago

edflsafoiewq 2y ago
My summary: The mesh for rendering and the mesh for collision detection are separate, so the first cause of "invisible walls" is just that a wall exists in the collision mesh but not in the render mesh. The other causes are mostly all because of tiny gaps in the level geometry. The game doesn't want to let you go somewhere where there is no floor below you, or there is a ceiling below you with no floor between you and the ceiling. (A floor is just a collision tri with normal pointing up, a ceiling is one with normal pointing down.) If you try to move into one of these places, you hit an "invisible wall". Tiny gaps in the level geometry (eg. tiny misalignments of vertices) can create these places with no floor below them. The fact that collision detection is done with integer math, combined with certain geometric situations, make the game particularly prone to small gaps around the edges of platforms. The bulk of the video classifies these geometric situations in detail. The game does not do continuous/swept collision detection, but moves Mario in discrete steps. You only hit the "invisible wall" if you are unlucky enough to land exactly on the gap at the end of a step, which is why you only seem to hit them sometimes. This is the same reason you can pass through regular walls when you move fast enough. An exacerbating factor is a bug in the "check for floor under Mario" routine that the video calls "floor overshadowing" (the decomp calls it "surface cucking"). The game searches for the floor under you from highest to lowest, returning the first one below you... except there's no actual way to order tris in 3D space from "highest to lowest" (it uses the height of the first vertex in the tri). So a tri earlier in the list can "cuck" the correct tri later in the list, which can result in a floor between Mario and a ceiling not being found even when it exists.
Karuma 3y ago
[flagged]
- jdlshore 3y ago
  It failed—that’s just the preamble. The video’s probably too long for it. You should know better than to use AI without checking the results.
- CydeWeys 3y ago
  AI-generated comments are not allowed on Hackernews. See: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&query=by%3Adang%20%22generated%20comments%22&sort=byDate&type=comment https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
mondobe 3y ago
[video]
- Lammy 3y ago
  > (youtube.com)
stemlord 3y ago
How on earth does it take 4 hours to explain? I'm sure it's a lovely video but anyone care to tldr?
- ranger_danger 3y ago
  You should see the "0.5 A presses" video: https://www.youtube.com/watch?v=kpk2tdsPh0A https://www.youtube.com/watch?v=kpk2tdsPh0A
- Kikawala 3y ago
  https://www.youtube.com/watch?v=YsXCVsDFiXA&t=3228s https://www.youtube.com/watch?v=YsXCVsDFiXA&t=3228s
  - savrajsingh 3y ago
    This is exactly it, thanks!
  - VelesDude 3y ago
    Thanks for that. I will go through the whole video later but that at least covered the basic premise. Essentially, due to the technique used for collision detection, tiny gaps in the geometry causes collision system to treat parts of the scene as having very thin walls that stretch to the top of the play space. Depending on if Mario's quarter steps align with this little gap means that a collision can be made despite it not being visible. Also explains why they impact Mario sometimes and not others. Like throwing a marble through a mesh fence but you cannot see the fence. Odds are you will make it through but it is essentially chance.
- Waterluvian 3y ago
  I skimmed it and it’s trying to be the authoritative “phd thesis” on the topic. Still, many sections felt far too wordy and long. Technical communication is a difficult skill.
  - VS1999 3y ago
    True. If he wanted to make it a proper phd thesis he'd use language to muddy the waters so no one could understand what he was saying.
nimish 3y ago
There's something wholesome that there's someone out there with a PhD in Super Mario 64. Long live the eccentric.
bumbledraven 3y ago
This is a new explainer by pannenkoek2012, the video game researcher best known for his discussion of "parallel universes" in Super Mario 64. He rarely publishes for general audiences these days, and the description says this video took him 10 months to make. https://en.wikipedia.org/wiki/Pannenkoek2012 https://en.wikipedia.org/wiki/Pannenkoek2012 https://knowyourmeme.com/memes/05x-a-presses-but-first-we-need-to-talk-about-parallel-universes https://knowyourmeme.com/memes/05x-a-presses-but-first-we-ne...
g___ 3y ago
For over a decade, the author of this video has been leading an effort to complete Super Mario 64 with the smallest amount of A presses, often using extremely complex strategies. Here's a 5h video with the history. Bismuth says the history video took roughly 1500-2000 hours. https://www.youtube.com/watch?v=yXbJe-rUNP8 https://www.youtube.com/watch?v=yXbJe-rUNP8
redox99 3y ago
The amount of effort in this video is astounding. Quote from the author > If you’ve wondered where I’ve been for the past 10 months, it was working day and night on this one video. In other words, I never actually left, I’ve been working on sm64 the whole time. So I didn’t forget about you guys :)
allanrbo 3y ago
My goodness, 3+ hours on this topic! I truly admire the passion! Fascinating!
throwaway74432 3y ago
I don't mean to knock this video or anyone that gets a kick out of it. But does anyone else feel a sense of despair when they see that someone has put so much time and effort into something like this? I feel the same about speedrunners. Yes, they aren't hurting anyone, and yes they're following their passion, but I still feel an instinctual sense of despair when I see someone work so hard on something like this. I'm sincerely not trying to hate on anyone.
- fb03 3y ago
  Not really. I wish I had: - that much drive and - that much time to sink into pleasurable (useful or not) endeavor watching people talk about something they have a passion in (whatever that topic might be) is really interesting to me
- eddieroger 3y ago
  Some people really like to know how things work and are willing to put a lot of time in to understanding the thing that interests them. I don't feel despair. I'm glad they have a passion and feel so strongly about something that they wish to dedicate their time to their passion. If anything, I'm a little jealous. To each their own.
- vsnf 3y ago
  My despair is that you think he should have spent his effort on something you find, I assume, to be more productive than this. He’s an expert is a video game, it’s wonderful that we have the material abundance to allow that.
- bongodongobob 3y ago
  [flagged]
  - throwaway74432 3y ago
    I feel very deeply that my life is full of meaning, so it can't be projection. Not interested in trying to suppress my feelings with drugs either.
deleted 3y ago
[deleted]

136 points by mbStavola 3y ago

My summary: The mesh for rendering and the mesh for collision detection are separate, so the first cause of "invisible walls" is just that a wall exists in the collision mesh but not in the render mesh. The other causes are mostly all because of tiny gaps in the level geometry. The game doesn't want to let you go somewhere where there is no floor below you, or there is a ceiling below you with no floor between you and the ceiling. (A floor is just a collision tri with normal pointing up, a ceiling is one with normal pointing down.) If you try to move into one of these places, you hit an "invisible wall". Tiny gaps in the level geometry (eg. tiny misalignments of vertices) can create these places with no floor below them. The fact that collision detection is done with integer math, combined with certain geometric situations, make the game particularly prone to small gaps around the edges of platforms. The bulk of the video classifies these geometric situations in detail. The game does not do continuous/swept collision detection, but moves Mario in discrete steps. You only hit the "invisible wall" if you are unlucky enough to land exactly on the gap at the end of a step, which is why you only seem to hit them sometimes. This is the same reason you can pass through regular walls when you move fast enough. An exacerbating factor is a bug in the "check for floor under Mario" routine that the video calls "floor overshadowing" (the decomp calls it "surface cucking"). The game searches for the floor under you from highest to lowest, returning the first one below you... except there's no actual way to order tris in 3D space from "highest to lowest" (it uses the height of the first vertex in the tri). So a tri earlier in the list can "cuck" the correct tri later in the list, which can result in a floor between Mario and a ceiling not being found even when it exists.

Karuma 3y ago

[flagged]

jdlshore 3y ago
It failed—that’s just the preamble. The video’s probably too long for it. You should know better than to use AI without checking the results.
CydeWeys 3y ago
AI-generated comments are not allowed on Hackernews. See: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&query=by%3Adang%20%22generated%20comments%22&sort=byDate&type=comment https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

mondobe 3y ago

[video]

Lammy 3y ago
> (youtube.com)

stemlord 3y ago

How on earth does it take 4 hours to explain? I'm sure it's a lovely video but anyone care to tldr?

ranger_danger 3y ago
You should see the "0.5 A presses" video: https://www.youtube.com/watch?v=kpk2tdsPh0A https://www.youtube.com/watch?v=kpk2tdsPh0A
Kikawala 3y ago
https://www.youtube.com/watch?v=YsXCVsDFiXA&t=3228s https://www.youtube.com/watch?v=YsXCVsDFiXA&t=3228s
- savrajsingh 3y ago
  This is exactly it, thanks!
- VelesDude 3y ago
  Thanks for that. I will go through the whole video later but that at least covered the basic premise. Essentially, due to the technique used for collision detection, tiny gaps in the geometry causes collision system to treat parts of the scene as having very thin walls that stretch to the top of the play space. Depending on if Mario's quarter steps align with this little gap means that a collision can be made despite it not being visible. Also explains why they impact Mario sometimes and not others. Like throwing a marble through a mesh fence but you cannot see the fence. Odds are you will make it through but it is essentially chance.
Waterluvian 3y ago
I skimmed it and it’s trying to be the authoritative “phd thesis” on the topic. Still, many sections felt far too wordy and long. Technical communication is a difficult skill.
- VS1999 3y ago
  True. If he wanted to make it a proper phd thesis he'd use language to muddy the waters so no one could understand what he was saying.

nimish 3y ago

There's something wholesome that there's someone out there with a PhD in Super Mario 64. Long live the eccentric.

bumbledraven 3y ago

This is a new explainer by pannenkoek2012, the video game researcher best known for his discussion of "parallel universes" in Super Mario 64. He rarely publishes for general audiences these days, and the description says this video took him 10 months to make. https://en.wikipedia.org/wiki/Pannenkoek2012 https://en.wikipedia.org/wiki/Pannenkoek2012 https://knowyourmeme.com/memes/05x-a-presses-but-first-we-need-to-talk-about-parallel-universes https://knowyourmeme.com/memes/05x-a-presses-but-first-we-ne...

g___ 3y ago

For over a decade, the author of this video has been leading an effort to complete Super Mario 64 with the smallest amount of A presses, often using extremely complex strategies. Here's a 5h video with the history. Bismuth says the history video took roughly 1500-2000 hours. https://www.youtube.com/watch?v=yXbJe-rUNP8 https://www.youtube.com/watch?v=yXbJe-rUNP8

redox99 3y ago

The amount of effort in this video is astounding. Quote from the author > If you’ve wondered where I’ve been for the past 10 months, it was working day and night on this one video. In other words, I never actually left, I’ve been working on sm64 the whole time. So I didn’t forget about you guys :)

allanrbo 3y ago

My goodness, 3+ hours on this topic! I truly admire the passion! Fascinating!

throwaway74432 3y ago

I don't mean to knock this video or anyone that gets a kick out of it. But does anyone else feel a sense of despair when they see that someone has put so much time and effort into something like this? I feel the same about speedrunners. Yes, they aren't hurting anyone, and yes they're following their passion, but I still feel an instinctual sense of despair when I see someone work so hard on something like this. I'm sincerely not trying to hate on anyone.

fb03 3y ago
Not really. I wish I had: - that much drive and - that much time to sink into pleasurable (useful or not) endeavor watching people talk about something they have a passion in (whatever that topic might be) is really interesting to me
eddieroger 3y ago
Some people really like to know how things work and are willing to put a lot of time in to understanding the thing that interests them. I don't feel despair. I'm glad they have a passion and feel so strongly about something that they wish to dedicate their time to their passion. If anything, I'm a little jealous. To each their own.
vsnf 3y ago
My despair is that you think he should have spent his effort on something you find, I assume, to be more productive than this. He’s an expert is a video game, it’s wonderful that we have the material abundance to allow that.
bongodongobob 3y ago
[flagged]
- throwaway74432 3y ago
  I feel very deeply that my life is full of meaning, so it can't be projection. Not interested in trying to suppress my feelings with drugs either.

deleted 3y ago

[deleted]