Cube to cube collision

General
1

@Simeon I haven’t tried this before, but I have a question here. I have a sphere bouncing between 2 cubes. The sphere bounces off the bottom cube and also bounces off the top cube. But if I comment out the createSphere line to remove the sphere, the top cube passes thru the bottom cube. Just curious why the cubes don’t collide, but they both collide with the sphere.

viewer.mode=FULLSCREEN

function setup()
    assert(OrbitViewer, "Please include Cameras as a dependency")
    scene = craft.scene()
    skyMaterial=scene.sky.material
    skyMaterial.sky=color(0, 62, 255, 255)
    skyMaterial.horizon=color(99, 255, 0, 255)   
    scene.sun.rotation=quat.eulerAngles(20,45,-30)
    v=scene.camera:add(OrbitViewer, vec3(0,0,0), 150, 0, 500)
    v.rx,v.ry=10,20
    createFloor()
    createRect(0,15,0)
    createSphere(0,0,0)
end

function draw()
    update(DeltaTime)
    scene:draw()    
end

function update(dt)
    scene:update(dt)
end

function createFloor() 
    floor=scene:entity()
    f=floor:add(craft.rigidbody,STATIC)
    f.restitution=1
    floor.position=vec3(0,-20,0)
    floor.model = craft.model.cube(vec3(100,1,100))
    floor:add(craft.shape.model,floor.model)
    floor.material = craft.material(asset.builtin.Materials.Standard)
    floor.material.map = readImage(asset.builtin.Surfaces.Basic_Bricks_AO)
end

function createRect(x,y,z) 
    rec=scene:entity()
    rc=rec:add(craft.rigidbody,DYNAMIC)
    rc.restitution=1
    rec.position=vec3(x,y,z)
    rec.model = craft.model.cube(vec3(5,5,5))
    rec:add(craft.shape.model,rec.model)
    rec.material = craft.material(asset.builtin.Materials.Standard)
    rec.material.map = readImage(asset.builtin.Surfaces.Basic_Bricks_AO)
end

function createSphere(x,y,z)
    local sphere1=scene:entity()
    local sph=sphere1:add(craft.rigidbody,DYNAMIC)
    sph.restitution=1
    sphere1.position=vec3(x,y,z)
    sphere1.model = craft.model.icosphere(1,2)
    sphere1:add(craft.shape.sphere,1)
    sphere1.material = craft.material(asset.builtin.Materials.Specular)    
    sphere1.material.diffuse=color(0,0,255)
end
2

very weird. i don’t see anything that would explain it.

3

Not sure why a cube to cube collision doesn’t happen when a sphere to cube collision works. Here’s a way I got around it just in case anyone else needs to do it. It’s a straight on collision, so the cube won’t rotate on any off angle collisions. I just embedded a sphere within the cube. The sphere does the collision and the cube just stays with it.

viewer.mode=FULLSCREEN

function setup()
    assert(OrbitViewer, "Please include Cameras as a dependency")
    scene = craft.scene()
    skyMaterial=scene.sky.material
    skyMaterial.sky=color(0, 62, 255, 255)
    skyMaterial.horizon=color(99, 255, 0, 255)   
    scene.sun.rotation=quat.eulerAngles(20,45,-30)
    v=scene.camera:add(OrbitViewer, vec3(0,0,0), 150, 0, 500)
    v.rx,v.ry=10,20
    createFloor()
    createRect(0,15,0)
    createSphere(0,15,0)
end

function draw()
    update(DeltaTime)
    rec.position=sphere1.position
    scene:draw()    
end

function update(dt)
    scene:update(dt)
end

function createFloor() 
    floor=scene:entity()
    f=floor:add(craft.rigidbody,STATIC)
    f.restitution=1
    floor.position=vec3(0,-20,0)
    floor.model = craft.model.cube(vec3(100,1,100))
    floor:add(craft.shape.model,floor.model)
    floor.material = craft.material(asset.builtin.Materials.Standard)
    floor.material.map = readImage(asset.builtin.Surfaces.Basic_Bricks_AO)
end

function createRect(x,y,z) 
    rec=scene:entity()
    rc=rec:add(craft.rigidbody,DYNAMIC)
    rc.restitution=1
    rec.position=vec3(x,y,z)
    rec.model = craft.model.cube(vec3(5,5,5))
    rec:add(craft.shape.model,rec.model)
    rec.material = craft.material(asset.builtin.Materials.Standard)
    rec.material.map = readImage(asset.builtin.Surfaces.Basic_Bricks_AO)
end

function createSphere(x,y,z)
    sphere1=scene:entity()
    sph=sphere1:add(craft.rigidbody,DYNAMIC)
    sph.restitution=1
    sphere1.position=vec3(x,y,z)
    sphere1.model = craft.model.icosphere(2.49,2)
    sphere1:add(craft.shape.sphere,2.49)
    sphere1.material = craft.material(asset.builtin.Materials.Specular)    
    sphere1.material.diffuse=color(0,0,255)
end
4

@skar The rec.model sets the size of the cube, 5x5x5, and the sphere1 sets the radius of the sphere, 2.49 or a diameter of 4.98 . The diameter of the sphere has to be smaller than the side of the cube or it doesn’t work. So the model sets the shape, cube or icosphere. The other code sets the position, texture, color, bouncyness, and the body type DYNAMIC.

rec.model = craft.model.cube(vec3(5,5,5))

sphere1.model = craft.model.icosphere(2.49,2)
sphere1:add(craft.shape.sphere,2.49)
5

@dave1707 - ingenious but just a backstop, is this a fault in the physics library?

6

@dave1707 - I take it three spheres works fine. Sounds like the physics definition of cubes is missing something.

7

@Bri_G Sphere collision is easy, just the standard billiard ball calculations. But I guess trying to do a cube collision would be a lot harder considering the different angles and surfaces that would be involved. I have code where there’s a lot of spheres colliding and bouncing off walls. Those work just fine.

8

@Bri_G I’m not sure if it’s a fault, or I’m doing something wrong, or maybe trying to do a cube to cube collision is too difficult trying to figure out the angles and rotation, etc. This is the first time I tried to do a cube to cube collision after I don’t know how many years, so I don’t think it’s going to bother me that much.

Just curious why it doesn’t work.

9

how does this work? where is the size and shape of the body defined?

rc=rec:add(craft.rigidbody,DYNAMIC)