Comments on: Integration Basics http://gafferongames.com Glenn Fiedler's Game Development Articles and Tutorials Tue, 08 May 2012 16:41:33 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-48667 Glenn Fiedler Tue, 08 May 2012 16:41:33 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-48667 Yep. Acceleration due to gravity is typically modeled as constant for jumping / ballistic projectiles etc. Yep. Acceleration due to gravity is typically modeled as constant for jumping / ballistic projectiles etc.

]]> By: Anonymous http://gafferongames.com/game-physics/integration-basics/#comment-48623 Anonymous Tue, 08 May 2012 10:55:35 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-48623 For a simple jump algorithm, would the acceleration function return a constant? For a simple jump algorithm, would the acceleration function return a constant?

]]> By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-48329 Glenn Fiedler Sun, 06 May 2012 16:01:46 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-48329 It's a useful exercise to think it through and rewrite like that. Congrats! It’s a useful exercise to think it through and rewrite like that. Congrats!

]]> By: Fredrik http://gafferongames.com/game-physics/integration-basics/#comment-48304 Fredrik Sun, 06 May 2012 13:00:03 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-48304 Apparently I got it right on my first try. I just didn´t realize I integrated momentum from force directly (which is what you wrote in your "physics for 3d" article) and then I spent 4 days rewriting my code to understand how momentum would fit in. But I got it right in the end and I even know what I´m doing now. :) Thank´s again for a great series of articles! It has really helped me out a lot! Apparently I got it right on my first try. I just didn´t realize I integrated momentum from force directly (which is what you wrote in your “physics for 3d” article) and then I spent 4 days rewriting my code to understand how momentum would fit in. But I got it right in the end and I even know what I´m doing now. :)

Thank´s again for a great series of articles! It has really helped me out a lot!

]]> By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-47601 Glenn Fiedler Wed, 02 May 2012 15:29:59 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-47601 And yes, you go from momentum -> velocity, then add the velocity to the previous position. Velocity is still used to update positions. It's just that momentum is a better quantity to use when dealing with ANGULAR motion, because angular momentum is conserved while angular velocity is not (except in special cases). Basically, if you are just doing linear motion -- there is no benefit to using momentum instead of velocity... And yes, you go from momentum -> velocity, then add the velocity to the previous position. Velocity is still used to update positions. It’s just that momentum is a better quantity to use when dealing with ANGULAR motion, because angular momentum is conserved while angular velocity is not (except in special cases).

Basically, if you are just doing linear motion — there is no benefit to using momentum instead of velocity…

]]> By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-47600 Glenn Fiedler Wed, 02 May 2012 15:27:51 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-47600 F = ma, therefore acceleration = F/m p = mv, therefore momentum = velocity * mass Basically, you integrate force directly to get linear momentum. Just don't divide force by mass to get acceleration before integration. cheers F = ma, therefore acceleration = F/m

p = mv, therefore momentum = velocity * mass

Basically, you integrate force directly to get linear momentum. Just don’t divide force by mass to get acceleration before integration. cheers

]]> By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-47599 Glenn Fiedler Wed, 02 May 2012 15:26:28 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-47599 In other words, the first integration is 100% accurate, but the second one (using the result of the first integration, which changes over time...) is not. In other words, the first integration is 100% accurate, but the second one (using the result of the first integration, which changes over time…) is not.

]]> By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-47598 Glenn Fiedler Wed, 02 May 2012 15:25:55 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-47598 We are integrating twice. First from acceleration to velocity, which is 100% accurate because the acceleration is constant. Then from velocity to position, which is not 100% accurate because the velocity is changing over time (and in fact, in "reality" is changing in between our sample points dt apart...) cheers We are integrating twice. First from acceleration to velocity, which is 100% accurate because the acceleration is constant. Then from velocity to position, which is not 100% accurate because the velocity is changing over time (and in fact, in “reality” is changing in between our sample points dt apart…)

cheers

]]> By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-47597 Glenn Fiedler Wed, 02 May 2012 15:24:36 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-47597 http://www.metanetsoftware.com/technique/tutorialA.html http://www.metanetsoftware.com/technique/tutorialA.html

]]> By: Glenn Fiedler http://gafferongames.com/game-physics/integration-basics/#comment-47596 Glenn Fiedler Wed, 02 May 2012 15:22:47 +0000 http://www.gaffer.org/wordpress/integration-basics/#comment-47596 Linear momentum is mass * velocity. Force is the time derivative of linear momentum. So to take force and go to momentum you just integrate force over time. There is an example of this in the source code for this article. cheers Linear momentum is mass * velocity. Force is the time derivative of linear momentum. So to take force and go to momentum you just integrate force over time. There is an example of this in the source code for this article. cheers

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