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Member Since 11 Nov 2010
Offline Last Active Sep 18 2014 12:31 PM

Posts I've Made

In Topic: Need very simple 3D collision testing - library or self-roll?

28 July 2013 - 06:10 PM

My situation is I'm a professional developer, my aim is not to learn for its own sake but to get something working in the shortest time. I like learning new tech BUT when in work mode chasing a specific deliverable, I prioritise the destination rather than the journey! Hence in this specific case where I know the requirements of the application do not involve more complex physics, I am purely after whatever would be quickest to implement overall smile.png


Bullet physics is really quick and easy to get up and running quickly but the documentation is a little sparse after that. 

In Topic: vertex shader particle physics kinematic formulas

25 July 2013 - 10:52 AM

The equation for drag coefficient is as follows,


Cd = 2*Fd/rho*v*v*A


where, Cd = Drag Coefficient,

Fd = drag force

rho = fluid density

v = object velocity

A = object surface area


Wait I'm confused. How can I know the velocity of the object in order to do the calculation if that's what I'm calculating? Also the equation for drag force contains the drag coefficient which in turn requires the force of drag to calculate. 

In Topic: vertex shader particle physics kinematic formulas

24 July 2013 - 05:37 PM

Heavy objects do not fall faster than light objects... They are simply heavier.


I know that in a vacuum this is always true but the mass to surface area ratio will effect the speed of falling when air resistance is taken into account.

In Topic: Need very simple 3D collision testing - library or self-roll?

24 July 2013 - 12:18 PM

I use Bullet for my physics engine but for simple intersection tests I use a homemade solution. Just a few functions like:

int sphereBoxTest(vec center, float rad, vec bMin, vec bMax);
int sphereSphereTest(vec center0, float rad0, vec center1, float rad1);
int sphereRayTest(vec center, float rad, vec start, vec end);

There dead easy to implement and plenty sample code exists on the internet. Using these tests for non physics related intersection tests (frustum culling etc) will keep bullet restricted to the physics portion of your code in case you want to ditch it at any point.

In Topic: Assimp loading indices not properly

23 July 2013 - 12:34 PM

make sure to use aiProcess_JoinIdenticalVertices in the flags or else the index buffer will not be necessary.