Sunday, 11 March 2012

Tennis ball bounce V7

Another entirely unsuccessful attempt to procure a tennis ball today. You wouldn't have thought they'd be so damn difficult to get hold of. Looks like I'm going to have to exercise my imagination a little bit longer...

I've sorted out weird jumping-forward problem from the previous post, so now the ball rolls forward at the end fairly nicely. I made a few more timing adjustments as well, speeding up the drop on the second bounce. I also slightly adjusted the height that the ball reaches on its first and second bounce - it seemed to go a little too high before, so I dropped it down just a tad and it seems a little better. I think the bounces are slowly getting there - though I think the third bounce (and perhaps the entire set of small bounces) are a bit too slow, but I'm not entirely sure? Might look at speeding them up. This is hard without reference.

The other big change is the addition of a little squashing and rotation. The ball squashes a lot more than I'd originally intended - at first, I only squashed it a very tiny amount and because the impact with the ground is so quick and instantaneous it didn't really 'read.' I slightly adjusted the curve so that the ball would remain close to the ground for a fraction of a second longer and also increased the amount of squash - looking at the capture it stands out far more than I thought it would, so I may reduce it slightly. Tennis balls are pretty firm!

I'm not sure if the rotation is at all accurate - probably not! I think it looks alright though (so far at least) so I'm probably not going to do too much tweaking to it, unless necessary. 

The other issue that probably isn't apparent from the angle of the shot is that the ball isn't actually touching the ground when it bounces. It's an issue I encountered whilst adding the squash to the ball - I could have fixed it straight away, but I decided to talk about it on the blog a bit first. I don't really know why. Maybe because it gives me an excuse to post some screen captures (which I've been neglecting so far)...

Basically, the rig seems to be set up in such a way that locks all its transformations to a local axis. The ball's centre point is positioned right on the bottom of the ball, so that when scaled along the y axis it squashes quite nicely. However, when a rotation is applied to the ball, the centre point follows - i.e. it's no longer on the bottom of the ball. This means that it scales from a slightly different point, meaning that the bottom of the ball is no longer touching the ground (as seen above).

It's not a big problem at all and I don't have any wonderfully clever solution - I'm just going to move the ball down so it's back in contact with the ground. I just thought it was worth talking about.

Maybe I'm just boring.

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