Tutorial: How to add IK targets to Sim rigs - Simplified step by step guide.
In this tutorial, you will learn how to add IK targets to Sim rigs, if you didn't know what IK targets are, they are a chain of bones (like hand>elbow>upper arm) that have an IK constraint on the last child bone (hand bone) and is set to target an IK target, to keep the hand in place. So basically, if the hand has an IK target, the hand will always stay in place unless you move the target.
This would be very useful for keeping feet in place while walking, so you wouldn't have to animate (if you do) the Sim's feet in place in every keyframe that the feet are on the ground. This would also help with keeping certain bones in place while moving the rig around, so you won't have to re-position the bones every time you move the rig.
You should at least understand the basics of Blender and know how to navigate around. I'm assuming you've already got all the requirements for this tutorial, but in case not you'll need all this ---> https://sims3cliptool.wordpress.com/download/
Step 1 Opening the Sim rig
Yep, it's as simple as that, just open any Sim rig file you want, in my case I'll just be using an adult rig I've customized a bit, but it's the same as the usual rigs.
Step 2 Adding the targets
Now here comes the fun part, adding the targets! It's actually really easy in fact, you'll learn how to add them in no time
So, first we'll add a target on the hand, so select one of the hand bones on the rig, then go to Pose > Inverse Kinematics > Add IK to Bone, and then a message will pop up saying "To New Empty Object" and "Without Targets" , select the first option. Now, a new empty object (target) will appear on the hand bone.
To scale down the empty object, either select it and scale it down by pressing "s" and moving your mouse inward or selecting the empty and going to it's properties (Object Data) and setting the size there (I would recommend a value such as 0.10). And to change the shape of the empty, go to it's properties and select whichever shape you would want. I typically use circles and spheres.
Here is where you would change values and shapes.
Now, when you select your rig's root bind bone, and move it around, the rig should move entirely in a strange way, but with the hand in place. But this is good, it means you've done everything good so far. So now let's make it so that when you move the rig, it should move normally but with the hand in place.
Step 3 Changing values and adding a chain length
This step is the most important one, if you want the targets to work properly. Now let's select the hand bone that has the target on, and go to Bone Constraints to see the IK constraint. What you'll do now, is set the chain length to 3, because 0 moves the entire body, and we only want the constraint to take effect from the hand up to the upper arm (up to the shoulder is optional, but it's usually not recommended). When you've done that, you should see a yellow line coming from the hand bone up to the last bone in the constraint (upper arm). Since the constraint is only taking effect from the hand up to the arm, when you move the empty, it should only move the entire arm. To finish off, check the "Rotation" box in the weight options. Your Sim rig's hand will look very broken when you check this, but you can easily fix it by rotating the hand back to a normal position by selecting the empty and rotating it with "r" or "r" twice for global rotating. Once it's all done, it should look like this:
And there! You've finished adding the target to the rig. Keep in mind, that when you move the rig too far away from the empty, the hand doesn't have a choice and will have to leave the target area (otherwise it would stretch the arm), but it's okay if that happens, because you can simply move your rig back to the empty area. Now all you need to do is repeat step 2 and 3 for the other hand bone and the feet bones.
Step 4 Naming the empty targets
This step is optional, but it will help you a lot to keep things organized, especially if you're working with multiple rigs or empties.
So, it's simple, just name the targets after the rig's age, gender and bone or side of the bone in the outliner. E.g. the target on the left hand bone can be named something like "af_L_HandIKTarget" or "a_IKTarget_L_Hand" and with the feet bones, the same but with "Foot" instead of "Hand".
And now you're done for good! You just learnt how to add IK targets to Sim rigs, well it's not anything too fancy but it's something else you've learned at least. If you would like a video to observe what you're doing better, I have one hosted one on my YT channel, here: https://www.youtube.com/watch?v=zLyRjp-15M8
Quick Disclaimer I am self taught with Blender and animation, so all that you've learnt right now is all I learnt myself, so there could be more tips out there, as well as tricks and better ways of performing this tutorial. I am a kid too, so if I don't make sense sometimes, or I use made up words (hardly ever though) that's my excuse. If you have any questions about this tutorial, feel free to ask them in this tutorial thread.
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