Questions About Physics
Community Forums/General Help/Questions About Physics
| ||
| What is a Concave body? What is a Convex Body? How acting on a rigid body in a physical system ? |
| ||
| 1) Sticks in. (Or generally has sticky in bits) 2) Sticks out. (Or generally doesn't have sticky in bits, like the ships in Elite original) 3) Is too badly phrased to answer (ie its Gibberish) |
| ||
Good one.. Rigid would be a non flexible, hard shape, such as above 2? Water or pudding would than be the opposite: non-rigid bodies. Not sure if in a physics engine these have a different meanings than in real life. |
| ||
| There is a technical definition of convex. A set ( body ) is convex if for EVERY pair of points in the set the line segment connecting those points is entirely contained in the set. For a 2D set imagine stretching a rubber band so that it fits around the set, then let it go. It snaps onto the set. If there is no empty space between the set and the rubber band then the set is convex. Another way to think of this is that no part of the surface of the set curves "inward". 3D is similar. You might imagine shrink wrap instead of a rubber band. The name "concave body" is a little misleading. It simply means non-convex. |
| ||
 ok , ay am understanding this better. Concave body physics system Bala, is not as accurate , for example if I try to put a chair in a plastic bag , that would be the concave system , collisions would not be as accurate, something that is Exato not put my chair in a system of body convex rigid where collision system is much more accurate. Now the other question is a hull leather. What is a Hull body? The word "Hull" in Spanish translates as "Bark", the peel of a banana and do not understand that it is a Hull body. |
| ||
| Hull body? Never heard that before. "convex hull" of a set of points means the smallest convex set which contains all the points. For the 2D case we can again use the rubber band stretched around the set. The convex hull of the set consists of all points enclosed by the rubber band. |
| ||
in physical Bullet System I have the Following command.btbodycreatetrimesh( mesh%, mass#, type%) ; type. ;TRIMESH_STATIC ;TRIMESH_CONVEX ;TRIMESH_CONCAVE btBodyCreateConvexHull%(mesh%, mass#, reduction%=True) ConvexHull? |
| ||
| Hull is "casco del barco", but here I think its more vaina. So better translation would be btBodyCubrirConGuante But that would give Concave results ;( |
| ||
ConvexHull Ok now I have come to understand a ConvexHull is like the picture, the collision is in the red lines. |
| ||
| A convex hull is an approximation of an arbitrary mesh. It's more optimised, so computing collisions\reactions is faster. Perceptually, it still feels the same as using the original mesh. The Blitz3D "ellipsoid-to-box, ellipsoid-to-ellipsoid" etc. collision modes are all hull approximations. It's much faster to calculate the collision of a parametrical volume such as that of an ellipsoid or a cuboid, than calculating the collision of every single triangle between two 5k triangle animated characters. |
| ||
| In Dutch we translate hull as skin. So.. a hull is basically as an elastic skin round an object, such as in the drawing above by Yue and is used for collisions. Interesting info. |
| ||
Well, at least now I have a vague idea of what I'm doing something to improve performance in my project. ;) |
| ||
| For me a "hull" is a "shell", the exterior side of one or several shapes. For example, with Blitz3d, you can use several ellipsoids to create a shape and this will help you to detect a collision between the exterior of the resulting shape and the collidables. |
| ||
| hull n. The dry outer covering of a fruit, seed, or nut; a husk. n. The enlarged calyx of a fruit, such as a strawberry, that is usually green and easily detached. n. Nautical The frame or body of a ship, exclusive of masts, engines, or superstructure. |
| ||
btWheelSetDirection(llantaPx%,0,-1,0) btWheelSetAxis(llantaPx%,-1,0,0) btWheelSetFront(llantaPx%,1) btWheelSetRadius(llantaPx%,15) btWheelSetSuspensionRestLength(llantaPx%,10) btWheelSetSuspensionStiffness(llantaPx,1.6) btWheelSetSuspensionDamping(llantaPx,2) btWheelSetSuspensionCompression(llantaPx,0.7) btWheelSetRollInFluence(llantaPx,0.19) btWheelSetFrictionSlip(llantaPx,1.6) Hi, I 'm trying to get my robot rises above the stones , I can not do , not how to translate these commands for correct configuration. I can help . |
   |