Strain as described by Tess is a real thing. When you have a series of jumps, the algorithm will calculate the aiming difficulty of each individual jump, and then this number is further increased as you have more jumps. That's strain, I think, but of the most simple variety.
If you have a series of jumps end on a spaced stream, that's a different matter. There is clearly a *lot* of effort that you need to put in order to hit all notes on the spaced stream at the end, but the current difficulty algorithm doesn't really take that into consideration, IMO. The effort you have to put to decelerate your cursor like that is definitely real, as B1rd said. I think this is also partly the reason why CS difficulty calculation is flawed and a flat bonus had to be put in place in order to fix star ratings for high CS maps.
That said, I don't think looking at angles alone is the way to implement a reading calculator. There are some good things you can do with it, but I don't think it's enough to fix highly overrated maps like Koigokoro. For that, you would need a pattern detector: an algorithm that looks at mapping patterns as a whole, instead of just calculating the angles from individual jumps. I'd say that if Tom wants to look into that, he should start very small and safe (as is many times the case in software developing), by testing individual patterns that are *for sure* a pain in the ass to everyone who plays this game and are also underrated by the current algorithm. I think that if you add a small batch of those to the current build, you would already be fixing DT farm maps by making everything else give much more PP. Alternatively, you could detect EASY patterns and then add a penalty, but to me that sounds more difficult.
If you have a series of jumps end on a spaced stream, that's a different matter. There is clearly a *lot* of effort that you need to put in order to hit all notes on the spaced stream at the end, but the current difficulty algorithm doesn't really take that into consideration, IMO. The effort you have to put to decelerate your cursor like that is definitely real, as B1rd said. I think this is also partly the reason why CS difficulty calculation is flawed and a flat bonus had to be put in place in order to fix star ratings for high CS maps.
That said, I don't think looking at angles alone is the way to implement a reading calculator. There are some good things you can do with it, but I don't think it's enough to fix highly overrated maps like Koigokoro. For that, you would need a pattern detector: an algorithm that looks at mapping patterns as a whole, instead of just calculating the angles from individual jumps. I'd say that if Tom wants to look into that, he should start very small and safe (as is many times the case in software developing), by testing individual patterns that are *for sure* a pain in the ass to everyone who plays this game and are also underrated by the current algorithm. I think that if you add a small batch of those to the current build, you would already be fixing DT farm maps by making everything else give much more PP. Alternatively, you could detect EASY patterns and then add a penalty, but to me that sounds more difficult.