2,060 reputation
420
bio website fxz.sufx.net
location Bucharest, Romania
age 28
visits member for 2 years, 1 month
seen 6 hours ago

Graphics programmer. Main interests:

  • physics based animation (deformable objects, kinematics)
  • mathematics of CG applications (simulation, games, etc.)
  • shader programming
  • discrete differential geometry (manifold properties)
  • robotics

Programming languages:

C++, PHP, C#, Objective C, Python, Java, Javascript/CSS/HTML, MATLAB, SciLab

Database:

MySQL, OracleSQL, MSSQL

Shading languages:

Cg, GLSL, HLSL

Libraries, engines, frameworks, tools:

OpenGL (CG library) , WiiBrew (HCI library), Ogre (CG Engine), Blender 3D (CG tool), GIMP (CG tool), Codeigniter (PHP framework), dotNet (C#, WPF especially)

.. strong Math skills (advanced Mathematics, Geometry and Calculus and Algebra)


Oct
16
comment physics of 2D car racing game with heightmap
How did you come up with the Pro and Contra arguments? Using rigid body physics is actually easier and more stable than tweaking stiff springs for your car (and it won't be very pleasant). Undoubtedly, Box2D can do the hard work for you: emanueleferonato.com/2009/04/06/two-ways-to-make-box2d-cars .
Oct
16
comment Efficient foliage rendering with OpenGL
@SeanMiddleditch this observation should be written in bold even!!
Oct
16
comment The physics equation for a perpetual seesaw
good efforts, I'll let you know if I spot something fishy. Overall, quite a read :)
Oct
16
comment The physics equation for a perpetual seesaw
What about a seesaw without any springs? (torsion springs in your case).. just a plain old, critically balanced lever? In theory, you could avoid the angular momentum/inertia tensor hacks altogether and just use the energy transfer + force equations. Anyhow, nice answer, but a bit too long. If you edit it a bit to make it straightforward to follow, it might be the best option!
Oct
15
comment The physics equation for a perpetual seesaw
@Mike, consider my scenario, where the falling object starts in contact with the lever/plank. The weight force from this object is then transferred via the lever (with a ratio) to the other object, altering its velocity. There is a moment in time when the other object will actually set off and fly/stop touching the lever. The falling body wastes some potential energy/work which gets transferred to your other body. If that body comes back, it will transfer this waste to the initial body, hence the energy will be conserved, as in real physics :D
Oct
15
comment The physics equation for a perpetual seesaw
Not only the energy transfer isn't 100% efficient, but it isn't instantaneous either. The amount of energy is usually transferred in a period of time. To cheat, the OP might consider it as an instant acceleration spike/or impulse that alters the other body's velocity. Extra energy is usually added by the action of the weight on the other end while the lever and the body are still in contact.
Oct
15
comment The physics equation for a perpetual seesaw
Well, it's not that trivial: when an object falls and hits a lever, it has to lower its kinetic energy that it accumulated while falling. Now, assume you just put the object exactly on the end of the lever and let gravity act on it (it should have zero kinetic energy to start with). Then indeed, the force involved in the equation is constant and it is constantly acting on the lever, thus setting in motion the other end object. The lever ratio will tell you the exact amount of acceleration the other object ends up with. In the other case, you need to consider the energy transfer as well :)
Oct
11
suggested suggested edit on Free Game Engine with Inverse Kinematics Support
Oct
11
comment Free Game Engine with Inverse Kinematics Support
This CCD implementation for Unity might do the trick -> buchhofer.com/2012/01/… . Apart from that, you can code CCD (graphics.ucsd.edu/courses/cse169_w04/welman.pdf ) yourself (it takes less than a few hours).
Oct
7
revised Correct rotation with Quaternion
added 483 characters in body
Oct
7
comment Correct rotation with Quaternion
That's really not gimbal lock. I forgot to modify the angle computation :(.. sorry. You're not supposed to accumulate angle offsets like in my initial code, you must directly use them to update the quaternion. The quaternion update will accumulate the correct rotation offset.
Oct
7
revised Correct rotation with Quaternion
deleted 1 characters in body
Oct
7
comment Correct rotation with Quaternion
I've corrected a mistake (not updating the quaternion) and I've added a few remarks you should really consider to achieve a more synchronized effect
Oct
7
revised Correct rotation with Quaternion
corrected the logic
Oct
7
comment Correct rotation with Quaternion
related: gamedev.stackexchange.com/questions/23238/…
Oct
7
answered Correct rotation with Quaternion
Oct
7
comment Correct rotation with Quaternion
I'm gonna have to throw a remark at you: quaternion operations can also easily lead to gimbal lock! See this for an explanation opengl.org/discussion_boards/showthread.php/… . However, a gimbal lock occurs if and only if one axis moves rigidly with another (i.e. you really have a gimbal-like joint hierarchy). Your problem surely comes from how you compute your rot quaternion. To solve it, try and directly compute the axis of rotation and the angle, instead of composing two rotations... and rotates on wrong axes = in what way?
Oct
4
comment Algorithm for creating tree-like network structures
Do you already have nodes and adjacencies between them established, or you need to generate completely random trees? Do you have any cycles? (if so, please remove the <tree> tag)
Oct
4
comment Algorithm for creating tree-like network structures
Nice links, but could you briefly explain (a phrase or two) how the procedural generation of tree graphs could be adapted to more general, planar graphs? That should solve the OP's problem directly. Mind you, the OP already has the vertices and edges in place, but they don't know how to actually place the nodes and edges in a 2D plane without having overlaps. While a tree has no cycles and is trivial to draw, a more general graph might requires something more complicated.
Oct
4
comment Algorithm for creating tree-like network structures
@ktodisco Spot on en.wikipedia.org/wiki/Kuratowski's_theorem !!