src/testmod/java/org/saturnclient/emotes/testmod/TestAnimations.java

@@ -72,8 +72,9 @@ final class TestAnimations {
     }
 
     /**
-     * Squatting with knees out, hips pushed back and the chest leaning forward, bouncing the hips
+     * Squatting with knees out and hips pushed back, bouncing the hips about 2.5 times a second. The
-     * about 2.5 times a second. The torso and knees bend with the bounce, so the back arches.
+     * torso tips forward around the hips and bends backwards, so the lower back arches in (not a
+     * hunched back) and the chest comes up. The arch deepens at the top of each bounce.
      */
     private static Pose twerk(float t) {
         // 0 at the bottom of the bounce, 1 at the top.
@@ -82,22 +83,39 @@ final class TestAnimations {
         float thighPitch = -1.1f + 0.15f * up;
         float knee = 1.75f - 0.3f * up;
         float splay = 0.55f;
-        float lean = 1.25f - 0.2f * up;
+        // How far the torso tips forward at the hips, and how much of that the arch takes back by the
+        // chest. The chest ends up leaning forward by tilt - arch.
+        float tilt = 1.4f;
+        float arch = 0.4f + 0.3f * up;
 
         // Lower everything by as much as the bent legs got shorter, and push the hips back so the feet
         // stay under where they were (a rigid thigh + shin approximation of the curved leg).
         float drop = 12 - 6 * (float) (Math.cos(thighPitch) + Math.cos(thighPitch + knee)) * (float) Math.cos(splay);
         float back = -6 * (float) (Math.sin(thighPitch) + Math.sin(thighPitch + knee));
 
-        BoneTransform shift = new BoneTransform(0, drop, back, 0, 0, 0, 0, 0);
+        // The body pivots at the neck, so tipping it forward swings the hips back. Move the pivot so
-        // The arms ride on the chest, which would swing them back as it leans. Tilt them forward by a
+        // the hips stay on the legs.
-        // bit more than the lean so they hang down towards the knees, a little outside them.
+        float cos = (float) Math.cos(tilt);
-        float armPitch = -lean * 1.1f;
+        float sin = (float) Math.sin(tilt);
+        float bodyY = drop + 12 - 12 * cos;
+        float bodyZ = back - 12 * sin;
+
+        // The head and arms only turn with the torso's bend, not its rotation, so they get the tilt
+        // themselves (tilt plus the bend's turn is the chest's lean) and sit where the tipped torso puts
+        // them: the neck at the body's pivot, the shoulders 2 pixels down it.
+        float chest = tilt - arch;
+        float shoulderY = bodyY + 2 * cos - 2;
+        float shoulderZ = bodyZ + 2 * sin;
+        // Arms riding on a leaning chest would swing back, so tilt them forward to hang to the knees.
+        float armPitch = tilt - chest * 1.1f;
+        // Follow the chest, then look up by half its lean.
+        float headPitch = tilt - chest * 0.5f;
+
         return Pose.builder()
-                .set(Bone.BODY, shift.withBend(lean, 0))
+                .set(Bone.BODY, new BoneTransform(0, bodyY, bodyZ, tilt, 0, 0, arch, (float) Math.PI))
-                .set(Bone.HEAD, new BoneTransform(0, drop, back, -lean * 0.5f, 0, 0, 0, 0))
+                .set(Bone.HEAD, new BoneTransform(0, bodyY, bodyZ, headPitch, 0, 0, 0, 0))
-                .set(Bone.RIGHT_ARM, new BoneTransform(0, drop, back, armPitch, 0, 0.3f, 0.5f, 0))
+                .set(Bone.RIGHT_ARM, new BoneTransform(0, shoulderY, shoulderZ, armPitch, 0, 0.3f, 0.5f, 0))
-                .set(Bone.LEFT_ARM, new BoneTransform(0, drop, back, armPitch, 0, -0.3f, 0.5f, 0))
+                .set(Bone.LEFT_ARM, new BoneTransform(0, shoulderY, shoulderZ, armPitch, 0, -0.3f, 0.5f, 0))
                 // Knees fold back and a little inwards, so the thighs splay out and the feet come in.
                 .set(Bone.RIGHT_LEG, new BoneTransform(0, drop, back, thighPitch, 0, splay, knee,
                         (float) Math.PI - 0.35f))