Question...smooth undulation?
Blitz3D Forums/Blitz3D Programming/Question...smooth undulation?
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| Ok, I'm trying to make a value go from say...1 to 3 and back again (looping of course), smoothly. This value is used to move an object move up and down, so as it gets closer to 1 or 3 the value needs to be smaller. The most common use I've seen is for making waves by moving vertexes up and down. I believe the sin and cos commands are capable of doing what I'm after, but sadly that's one of those things that has always gone over my head. So anyway, putting it simply: I want an object to move on it's Y axis between 1 and 3 units. I want it to move up and down smoothly, with a wave-like motion. Can anyone help me out here? |
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| y = Sin(frame * 2)+2 hope this help :) cya |
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| sin(0)=0, sin(90)=1, sin(180)=0, sin(270)=-1, sin(360)=sin(0) - im guessing you can see the pattern, the values produce a smooth waveform.. the results are within unit range, so you can simply scale the result by a const - so if you want the max height of your wave to be 1000, sin(n)*1000. with some experimenting you shouldnt have too many problems putting something half decent together.. try passing time into the sin function... sin(millisecs()) EDIT: jst a small note, you should probably stick to using time based movement...units per sec, using frame based inputs will yield unpredictable ouput on fast/slow machines. hope that helped a little. |
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| Currently my engine is on a frame limiter (60 FPS), using Mark's framework example, though I'm not sure if that's the best route to take. Thanks for the examples guys, I'll expirement a bit with sin and see what the results are in game! I may start another thread later about going with time based engine instead of frame based...now that you've brought the topic up in my mind... -Jonathan |
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| Well I tried it out...using milisecs in it caused some really obvious jerkiness, so what I did was create a looping step value for the items, which increases by one every update up to 180, then resets to 0. This value is fed into the sin function, then 2 is added to the result. The items undulate up and down exactly as I wanted! I suppose the other method might be better if I used a time based engine instead of frame based... |
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| I used millisecs as a hint - no a solution. - its jerky cuz the steps are big..it wont take long for 90 millisecs() to elapse ;) The solution is to rewrite your system - make it time based, and update a step var in small increments every so many millisecs...how you implment such a system is up to you, but i imagine there are plenty of resources around that will help you create a "per sec" type system. anyway - glad you got it working ;) |
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