# Tagged Questions

Bullet is a professional, free 3D Game Multiphysics Library that provides state of the art collision detection, soft body and rigid body dynamics.

64 views

### Is restitution the wrong value, to make bouncing objects?

I have been experimenting with Bullet. Specifically I was modifying the Hello World tutorial, to make the ball bouncing. The first thing I noticed is, that I need to set both the restitution of the ...
73 views

### Java 3D collision detection with JBullet

So I have spent a long time trying to work on a collision detection system from scratch for own game engine and came up fruitless due to lack of time. Finally I decided to try to use Jbullet to try to ...
45 views

### Simulate a velocity sensor attached to a softbody node with bullet physics

I try to implement a virtual three-axis velocity sensor attached to a softbody node. The node already provides it's global position, normal and velocity, but how to calculate it's local velocity to ...
36 views

### Bullet Physic: Stack transformations on body after adding

How can I stack multiple transformations on a body? I mean... Rotate, translate and then rotate again? If I understood, a transformation on a rigid body can be made like this: btTransform ...
85 views

### issue with ray/physics collision detection

All, I am trying to pick object using ray collision and bullet physics I am initializing my projection and view matrix only once, here is the code projectionMatrix = glm::perspective(90.0f, 4.0f ...
83 views

### Simple Bullet Physics Collision Detection

I've been looking into bullet physics a lot here lately to handle my collision detection. I was using XNA collision but once I started to implement momentum into my physics simulation true and false ...
26 views

### Bullet btGImpactCollisionAlgorithm

I have a question about Bullet and in particular GImpact. When, the collisiontestpair(a, b) is called where GImpact pair check algo will be called on the btGImpactMeshShape, does it do a AABB tree ...
7 views

### doll lift by applying force and gravity force [duplicate]

Ｉwant to lift the doll by applying force to box rigidbody. Doll has a few rigidbody and constraint. Then set gravity ZERO, don't work well. please tell me!
187 views

### Bullet Physics - Collision not working when moving btBvhTriangleMeshShape

I have a robot (btTriangleMeshShape for each component) and a chain of boxes used as a cable, which is anchored on two components of the robot. I want to rotate a robot component and when this ...
174 views

### How to Load a Level for use with the Bullet Physics Library

I am trying to use a level in .obj format loaded with Assimp to generate a btBvhTriangleMeshShape to use with the Bullet physics library. I can successfully load btConvexHullShapes as well ...
299 views

### unity3d - Fire bullet using AddForce is very slow

This is a top-down view but in 3D coordinates, I would like to instantiate and fire a bullet from the player's gun. This script is on a spawner object at the end of the barrel. void Fire () { ...
100 views

### Improving performance for flocking behavior?

I have a game that I am trying to make. It is a twin-stick shooter that I want to design to have a LOT (Up to 500) of enemies on the screen. The game's base design comes from that of Geometry Wars, ...
93 views

### server/client architecture, how to combine physics data, scene graph and database over the network?

I'm writting a C++ server and a C++ client for a rpg game. The client is using OpenSceneGraph for rendering the 3D. RakNet is used for communication between the client and server. At this time, the ...
153 views

### Using Blender to define physics objects for libGDX

I'm in the early stages of building a game using libGDX. The game is 3D and will use Bullet physics (gdx-bullet wrapper). I have a 3D scene loaded and have manually created some physics objects which ...
23 views

### Launching projectile from a “canon” [duplicate]

I'm working on "Scorched earth"-like game just for learning purpose. I can't figure out how to launch the projectile from my tank's position, with a power of X ([0,100]),at an angle of Y ([-180,180]). ...
49 views

### How can motion/simulation be suspended for a given orientation of the body in bullet physics?

I am currently trying to make a Ragdoll and it falls to the ground obeying constraints as expected but it never actually comes to rest. The rigid bodies appear to vibrate and the Ragdoll starts moving ...
33 views

### Java JBullet rotating rendered rigidbodies

Hello I wan't to rotate object I wrote some piece of code but that don't won't to work. Here is this code: glPushMatrix(); float[] matrix = new float[16]; ...
137 views

### Java JBullet Mesh collsion problem

I have a problem with JBullet mesh collsion. Everything works fine when I create a mesh from my object without scaling, but the problem starts when I want to scale the object. I also tried scaling in ...
157 views

### Projectile Delta Movement

I'm running into an issue where I can't get the Projectiles to travel in the right direction, I'll admit my trig is a little rusty, anyone know how below might be improved? I am trying to get the ...
432 views

### Bullet Physics - scaling

I have added Bullet to my game engine. So far I am using translation and rotation, and it works fine. But now, I want to scale my geometry (eg. user can drink some potion an became small :-)). I am ...
197 views

### Trying to bounce a box with a plane using bullet physics

I'm trying to simulate a box that bounces with a plane and I'm beginner with bullet physics. I created a plane (box) and and a box that is falling. The problem is the ball is stalled while colliding ...
76 views

### Understanding HingeConstraint in jBullet

I'm using the java port of BulletPhysics engine jBullet. I'd like to make a joints between 2 triangles so that one edge of the first and one edge of the seconds act like a hinge. But I don't ...
78 views

### Bullet pointer becoming zero [closed]

I am currently trying to implement the Bullet physics into my game project. However, when i add some rigid bodies to the scene, i occasionally get an error in btDbvtBroadphase.cpp at the line ...
163 views

### How can I get a 4x4 matrix from a bullet quaternion?

I'm trying to make a game using JavaScript with Ammo.js ( an implementation of bullet ) and Sylvester to do my matrix maths. The problem is I don't know how to turn the WXYZ that bullet gives into the ...
320 views

### In a TPS, how to aim bullets to the direction the camera is pointing, but make the shooting from the player?

(In C#/XNA.) I mean, I can't find an answer nowhere. I'm trying to learn how to make a Third Person Shooter, especially like the one I found in a game called "M.A.R.S.", from Epic Games. I don't want ...
173 views

### Multiplayer and creeps (NPC enemies): how to compute bullet hits given the lag?

We are making a multiplayer co-op game, where players will shoot not each other but AI enemies (creeps), controlled by the game. The chosen implementation is client-server with an authoritative ...
400 views

### Friction not working for Vehicle in BulletPhysics

I am creating a vehicle using bullet-physics engine (v 2.82). I created a ground ( btBoxShape ), a box and a vehicle (following the demo). But friction between ground and vehicle wheels seems not ...
137 views

### Libgdx, find Vector3 direction

I am using Libgdx along with Bullet physics. I have a vehicle moving. I would like to use a ray from the vehicles origin and in the vehicles forward direction. How can I create the forward Vector3 ...
241 views

### Bullet - objects falling through

I have problem with bullet collisions. You can see problem on this video (around 0:18): http://goo.gl/DiVP8l Objects are "embeded" inside vertical bars - that is not correct - they should be ...
853 views

### What torque should I apply in Bullet to maintain a vertical orientation?

I have a RigidBody in Bullet. Each frame, I want to apply torque to correct its orientation toward an upright position (i.e. near-zero pitch and roll). I know its angular velocity and orientation. ...
142 views

### Irregular oval collision detection

I am using a physics library based on the Bullet physics engine. How do I create an egg shaped object or a cylinder where the width differs from the depth (i.e. with an oval shape)? I'm not looking ...
464 views

### How can I use imprecise accelerometer data for controls?

I want to rotate an object with respect to the phone's position. I use the accelerometer output to detect orientation: float roll = Gdx.input.getRoll(); float pitch = Gdx.input.getPitch(); float ...
390 views

### Bullet 3D Physics Objects Not Rotating?

So I've got Bullet 3D controlling the motion of objects rendered with DirectX. In the clipping below I've got 2 identical rectangles & 5 balls. The lowest rectangle has a mass of 0 and doesn't ...
801 views

### How to implement a simple bullet trajectory

I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which ...
52 views

### Bullet Physics ConvexDecomposition?

I've looked at Bullet Physics ConvexComposition Demo and would like to implement that in my game but the code is so undescriptive and it's hard to understand what is going on. Would any of you people ...
283 views

### Using Bullet physics engine to find the moment of object contact before penetration

I would like to use Bullet Physics engine to simulate the objects in 3D world. One of the objects in the world will move using the position from 3D mouse control. I will call it "Mouse Object" and ...
825 views

### LibGDX - draw bullet physics bounding box

I am very new to game development and I am trying to debug my 3d collision bounds. Could somebody give me an example on how to draw the collision bounds of an object in libGDX? I assume it has ...
56 views

### Bullet: Get steepness or slope between positions

In a CharacterController object, there is setMaxSlope(btScalar slopeRadians) The max slope determines the maximum angle that the controller can walk up. But how about knowing it in advance? Like ...
247 views

### Quaternion - rotating rigidBody to particular angle over time

Using Bullet Physics. There's a rigid body that is rotated. For some delta-time I need to rotate that body to have rotation of (0, y, 0) - keep the old y value rotation but reset x and z. The ...
692 views

### Conceptual - What is the optimal way to combine steering behaviors with rigid body physics?

I am working on a simple 3D space simulator that makes use of the Bullet physics engine. The spaceships are rigid bodies that have a mass and hitbox so that they can be considered for collisions. At ...
176 views

### Bullet softbody nodes messed up positions [closed]

I recently switched from Havok physics to Bullet because I wanted to have soft body collisions, but I don't have any budget to license the (superior?) Havok solution, I couldn't even try those ...
287 views

### What are the parameters for btHingeConstraint::setLimit

What does each parameter in btHingeConstraint::setLimit do to the hinge constraint? void btHingeConstraint::setLimit ( btScalar low, btScalar high, btScalar _softness = ...
122 views

### Bullet3: Issue with applying force once an object is at rest

I just started using bullet and I'm having an issue where once my rigid body is at reset at the floor it won't move when I apply a force to it. I have created a small demo to show this using the ...
633 views

### How to draw a plane equivalent to a given btStaticPlaneShape using OpenGL

With all other shapes in bullet, you can easily get the transform from the MotionState which holds the origin, the scale, and the rotation. There seems to be no way to get the same information about a ...
122 views

### x-inverted obj importer in BulletSharp - whats wrong?

See importer C# code at the repository. Screenshot: Left: bullet imported version, right: correct 3ds max version. It's somehow inverted. If you think that left part is just 180 degrees rotated you ...
223 views

### making rigid body stop using friction

how am I suppose to apply friction to an object so that when I apply force it decelerates eventually to zero? Here are my physics objects: Rigid Body "Sphere" Collision shape: btSphereShape(0.50) ...
336 views

### Spherical / Relative Gravity

I'm working on an Ogre3D + Bullet project that involves planets in a solar system. For all intents and purposes, I'm looking to give each planet it's own gravity sphere. So far, all I've found are ...
566 views

### How to use Bullet physics with Entity Component Systems?

I have an Entity Component system and I want to have a Physics Component that would add the given object to the physics simulation. My problem arises because the Bullet API requires me to add each ...