From f4346b8f06653dbc1e0c346d88f5f83ca8a7b876 Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Wed, 22 Mar 2023 23:06:40 -0500
Subject: re-implement bouncing ball

---
 main.lua | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

(limited to 'main.lua')

diff --git a/main.lua b/main.lua
index d6971b7..9f26eb3 100644
--- a/main.lua
+++ b/main.lua
@@ -6,11 +6,53 @@ local Vec3 = honey.Vec3
 local Mat4 = honey.Mat4
 local ecs = honey.ecs
 local systems = honey.standardSystems
+local ode = honey.ode
 
 
 -- initialize honey
 local window = honey.init()
 
+-- setup physics
+local world = ode.WorldCreate()
+local space = ode.HashSpaceCreate(ode.Space0)
+ode.WorldSetGravity(world, 0, -10, 0)
+ode.WorldSetCFM(world, 1e-5)
+ode.CreatePlane(space, 0, 1, 0, 0)
+local contactgroup = ode.JointGroupCreate(16)
+local body = ode.BodyCreate(world)
+local geom = ode.CreateSphere(space, 0.5)
+local mass = ode.MassCreate()
+ode.MassSetSphere(mass, 1, 0.5)
+ode.BodySetMass(body, mass)
+ode.GeomSetBody(geom, body)
+ode.BodySetPosition(body, 0, 3, 0)
+
+function physicsStep()
+	ode.SpaceCollide(space, function(o1, o2)
+		local b1 = ode.GeomGetBody(o1)
+		local b2 = ode.GeomGetBody(o2)
+		local contact = ode.CreateContact{
+			surface = {
+				mode = ode.ContactBounce + ode.ContactSoftCFM,
+				mu = ode.Infinity,
+				bounce = 1.0,
+				bounce_vel = 0.1,
+				soft_cfm = 0.001,
+			},
+		}
+		local collisions = ode.Collide(o1, o2, 1)
+		if #collisions > 0 then
+			print("collision detected!")
+			ode.ContactSetGeom(contact, collisions[1])
+			local joint = ode.JointCreateContact(world, contactgroup, contact)
+			ode.JointAttach(joint, b1, b2)
+		end
+	end)
+	ode.WorldQuickStep(world, 0.01)
+	ode.JointGroupEmpty(contactgroup)
+end
+
+
 -- create camera matrices
 local camera = {
 	view=Mat4():identity():translate(Vec3{0, 0, -60}),
@@ -79,6 +121,19 @@ local groundPlane = {
 }
 level:addEntity(groundPlane)
 
+
+local ball = {
+	transform=Mat4():identity(),
+	parent=false,
+	mesh=icosa,
+	shader=shader,
+	update=function(self, dt)
+		local x, y, z = ode.BodyGetPosition(body)
+		self.transform:identity():translate(Vec3{x, y, z})
+	end,
+}
+level:addEntity(ball)
+
 -- close window on ESCAPE key
 window:setKeyCallback(function(_, key)
 	if key == glfw.KEY_ESCAPE then
@@ -97,6 +152,7 @@ honey.loop(window, function(dt)
 	gl.ClearColor(0.2, 0.4, 1.0, 1.0)
 	gl.Clear(gl.COLOR_BUFFER_BIT + gl.DEPTH_BUFFER_BIT)
 	level:update(dt)
+	physicsStep()
 end)
 
 -- clean up
-- 
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