IK example;

examples/Animation/2_Bone_IK/main.lua

@@ -0,0 +1,72 @@
+local function solve(root, target, control, lengths)
+  local T = vec3(target - root)
+  local C = vec3(control - root)
+  local R = vec3(0)
+
+  -- Basis
+  local bx = vec3(T):normalize()
+  local by = (C - bx * (C:dot(bx))):normalize()
+  local bz = vec3(bx):cross(by)
+
+  -- Matrix from basis
+  local transform = mat4(
+    bx.x, by.x, bz.x, 0,
+    bx.y, by.y, bz.y, 0,
+    bx.z, by.z, bz.z, 0,
+    0, 0, 0, 1
+  ):transpose()
+
+  local distance = #T
+  local x = (distance + (lengths[1] ^ 2 - lengths[2] ^ 2) / distance) / 2
+  local y = math.sqrt(lengths[1] ^ 2 - x ^ 2)
+  local solution = vec4(x, y, 0, 1)
+  return root + (transform * solution).xyz
+end
+
+function lovr.load()
+  boneLengths = { .6, .6 }
+  root = lovr.math.newVec3(0, 1.5, -.5)
+  target = lovr.math.newVec3(1.0, 1.5, -.7)
+  control = lovr.math.newVec3(.5, 2, -.6)
+  pointSize = .04
+  drags = {}
+end
+
+function lovr.update(dt)
+  -- Allow hands to drag any of the points
+  local points = { root, target, control }
+  for i, hand in ipairs(lovr.headset.getHands()) do
+    local handPosition = vec3(lovr.headset.getPosition(hand))
+
+    if lovr.headset.wasPressed(hand, 'trigger') then
+      for j, point in ipairs(points) do
+        if handPosition:distance(point) < pointSize then
+          drags[hand] = point
+        end
+      end
+    elseif lovr.headset.wasReleased(hand, 'trigger') then
+      drags[hand] = nil
+    end
+
+    if drags[hand] then
+      drags[hand]:set(handPosition)
+    end
+  end
+end
+
+function lovr.draw()
+  lovr.graphics.setColor(0xff80ff)
+  lovr.graphics.sphere(root, pointSize / 2)
+  lovr.graphics.sphere(target, pointSize / 2)
+  lovr.graphics.sphere(control, pointSize / 2)
+
+  lovr.graphics.setColor(0xffffff)
+  for _, hand in ipairs({ 'left', 'right' }) do
+    if lovr.headset.isTracked(hand) then
+      lovr.graphics.cube('fill', mat4(lovr.headset.getPose(hand)):scale(.01))
+    end
+  end
+
+  -- Draw a line from the root to the result from the IK solver, then to the target
+  lovr.graphics.line(root, solve(root, target, control, boneLengths), target)
+end

examples/init.lua

@@ -12,8 +12,9 @@ return {
   'Interaction/Hand_Tracking',
   'Environment/Grid',
   'Environment/Skybox',
+  'Animation/Playback',
+  'Animation/2_Bone_IK',
   'Custom_Mesh',
-  'Animation',
   'Physics',
   'PBR_Materials',
   'Postprocessing',