Add Deterministic option to IterateIK3D

[TokageItLab]

• Prerequisite Add BoneExpander3D and allow Spring / IK to set mutable bone axes #111815

If deterministic option is true, the previous frame's result is discarded. At this point, the new result is calculated from the bone pose excluding the IterateIK3D as the initial state. This means the result will be always equal as long as the target position and the previous bone pose are the same. However, if angular_delta_limit and max_iterations are set too small, the end bone of the chain will never reach the target.

Setting deterministic option is true and angular_delta_limit to 180 degrees will produce the same results as the old SkeletonIK in FABRIK.

Deterministic FABRIK3D:

Old SkeletonIK3D:

(As I mentioned in #110120 (comment), the handling of Tips differs）

[fire]

Reviewed the enhancement a little.

[fire]

Is there some reasoning behind the 20% magic constant?

[TokageItLab]

This review should be sent #111815, though there's no particular reason. I suppose it could be set as a fixed value by the EditorSetting.

FYI, the changes added to the behavior in this PR are only below; As explained, it simply resets the state before iteration.

3893c89

void IterateIK3D::_init_joints(Skeleton3D *p_skeleton, int p_index) {
	IterateIK3DSetting *setting = iterate_settings[p_index];
	if (!setting) {
		return;
	}
	cached_space = p_skeleton->get_global_transform_interpolated();
	if (setting->simulation_dirty) {
		_clear_joints(p_index);
		setting->init_joints(p_skeleton, mutable_bone_axes);
		setting->simulation_dirty = false;
	} else if (deterministic) {
		setting->init_joints(p_skeleton, mutable_bone_axes); // <- Here.
	}