mightcouldb1 Posted March 24, 2010 Share Posted March 24, 2010 Rapid changes in direction or position is a characteristic of turbulent flow. I am currently reading particles into VOPs via point clouds, and I am unsure how to measure the change from the previous frame's position. I want to do it this way even though I could get similar results using acceleration. That wont do me any good if a particle comes to a screeching halt though. Thanks! Jason Quote Link to comment Share on other sites More sharing options...
realer Posted March 24, 2010 Share Posted March 24, 2010 as far as i know velocity is the change of position from frame to frame .. so probably the thing you are really looking for is acceleration if lenght(velocity) > 0 ? Quote Link to comment Share on other sites More sharing options...
mightcouldb1 Posted March 24, 2010 Author Share Posted March 24, 2010 actually, I am looking for acceleration... It must be 4am! Hehe, thank you. Nice stuff by the way! Quote Link to comment Share on other sites More sharing options...
mightcouldb1 Posted March 24, 2010 Author Share Posted March 24, 2010 Ok so I have another question now... If I use a force where y=-10, my particles acceleration is -10 constantly. If acceleration is the change in velocity per frame, wouldn't this be different? Or am I missing something? Quote Link to comment Share on other sites More sharing options...
Macha Posted March 24, 2010 Share Posted March 24, 2010 (edited) Acceleration is the first derivative of velocity with respect to time: the rate of change of velocity. So, acceleration = difference_in_speed/difference_in_time. If you want that to be precise you can take the limit of it as difference_time -> 0, so differentiate if you know the function. That is unlikely however so you could just calculate a rough value based on 1 frame as your time difference. Edited March 24, 2010 by Macha Quote Link to comment Share on other sites More sharing options...
graham Posted March 24, 2010 Share Posted March 24, 2010 Acceleration is the change in velocity over a period of time (usually 1 second). From physics, the sum of all forces = mass * acceleration ( F = ma). If your force is -10 and your mass is 1, your acceleration will always been -10 in y. Starting with an initial velocity of 0, after 24 frames of ay=-10, Vy = -10. Quote Link to comment Share on other sites More sharing options...
mightcouldb1 Posted March 24, 2010 Author Share Posted March 24, 2010 (edited) Thank you both for the physics lesson. I guess my question now is: how can I grab the velocity of something from a previous frame in pops so that I can use it to find the acceleration? If I understand correctly, I can use vel2 - vel1 divided by the time increment to get the acceleration. Edited March 24, 2010 by mightcouldb1 Quote Link to comment Share on other sites More sharing options...
AndrewVK Posted March 25, 2010 Share Posted March 25, 2010 is that what You want? veldif.zip Quote Link to comment Share on other sites More sharing options...
mightcouldb1 Posted March 26, 2010 Author Share Posted March 26, 2010 is that what You want? I never thought about using nodes to store attributes the way you did. Thank you! Perfect solution. Quote Link to comment Share on other sites More sharing options...
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