REALSOFT 3D - SKELETONS, BONES & JOINTS TUTORIAL - PAGE 4



THE TUTORIAL: Part Four


Here in Part 4 we will be going through a process of CONSTRAINING the Skeleton Joints in our Hierarchy. If you think in real life terms, a real Skeletons joints are constrained in their movement. Put your left arm out to the left and Horizontal. From the shoulder you will notice you can raise the whole arm up and down, left and right and all around. Do the hokey, pokey ... oops, got carried away. In each movement you are constrained at the limits, next move - broken arm, ouch! Now still holding your arm horizontally bend your elbow / lower arm forward. Not much else you can do here. A different type of constraint.

So, as in the real world we can CONSTRAIN our Skeletons joints to emulate reality. Read on please ....




BEFORE WE CONTINUE. Do this!

Select the SPINE or UPPERMOST Skeleton in the Hierarchy. In the toolbar, over the workspace left click the STORE icon. This will store the current POSE of the hierarchy. If you do this at this stage, any mistakes you make with the constraints, wrong movements or otherwise, can be rectified for the most part by clicking on the NATIVE icon [ right of STORE ]. This defaults the Hierarchy back to the pose that was saved. Handy Tool!




Take a look at the First picture below. I have selected the ARM SKELETON. You might notice that it has gone yellow with red dots. This is because I left clicked the EDIT button, top left under the File Menu in the default environment. Right clicking on the Arm Skeleton in the Workspace and selecting EDIT will also give the same effect.

Click on the FIRST JOINT at the top of the arm in edit mode [ first red dot ]. Notice a blue, a green and a red line [ or combination + / - same ] appears at the joint. These represent the tools used to adjust the HEADING, PITCHING and BANKING constraints of that joint. In the picture below you might also notice that I have superimposed a PROPERTY WINDOW into the image. To get this property window right click on the ARM SKELETON object in the hierarchy as below and select PROPERTIES [ double clicking does the same thing ]. Select the SPEC tab in this window, then the JOINTS tab further down the panel and finally CONSTRAINTS. Here you can see the current state of constraint for the selected joint.

Under HEADING drag the MIN Slider to the left. Notice the RED line 'arcs' upward in the workspace. Now drag the HEADING / MAX Slider to the right. The RED line 'arcs' downward. You end up with a semi circle or less depending on how far you slide the sliders. Try the same for PITCHING and BANKING. This will adjust the GREEN and the BLUE line in the same manner as the RED. In real terms, how far you MIN / MAX the sliders in all three constraint angles will dictate the level of constraint OR how far a bone will move in any direction.

PITCHING min / max is left to right constraint. HEADING min / max is up and down constraint. BANKING min / max is twisting constraint.






Look at the next image below. This is one I made earlier .. as it goes on TV cook shows. In this case I have added HEADING and PITCHING constraints. I will leave it up to you to add BANKING constraints. With a real upper arm joint all three ARE in action. The amounts and values of the MIN / MAX in all three is up to you too. EXPERIMENT!

Once you are happy with the values for all angles you can try ANIMATING your new constraints. To do so, move the mouse cursor into the Workspace, move it onto the actual line of the green PITCHING constraint, somewhere left mid of the semi circle. The cursor should change to a PEN icon. Left Click once - a line appears from the joint RED DOT, out to where you clicked the semi circle. Move slightly left or right on the semi circle and left click again. NOW YOUR IN CONTROL. Just move the mouse left and right, the skeleton arm below this joint will move accordingly. Again EXPERIMENT, you will get the hang of this. Try the same on the HEADING and BANKING angles to see what they do.



The picture below shows my constraints set for all the joints in the arm. Note the constraint on the ELBOW joint - its a PITCHING angle only and at that it is forward only. In real life you cannot bend your elbow backwards. Well I can't anyway.






To the left is my Skeletal Hierarchy with all constraints added. Looks impressive. I hope you have also achieved this at this stage. If not take your time. Start all over if you have to. YOU WILL GET IT ...





This is the FINAL Step in this Tutorial. All along we have been building HALF a Skeleton Hierarchy. The reason for this - "Why do more work than you have to". RS3D provides a nice little tool that will build the other half for you. Select the SPINE SKELETON or Upper Most Skeleton in your Hierarchy [ see picture left, the insert ]. Now, click on the DUPMIR Button in the toolbar above the Workspace. This will immediately create the other half of the Skeleton Hierarchy for you [ See the picture below ].

STUDY the picture below. You will notice some Duplication of Skeletons. The Head Skeleton is Doubled. Select the second Head Skeleton object in the hierarchy and simply delete it. Now rename the Skeletons properly, as the copied / duplicated Skeleton names are the same as the originals. This can be seen in the BEFORE / AFTER Property inserts in the picture below.








FINALLY, FINALLY - there are other tools like ANCHORS and RIGID that one can play with. EXPERIMENT with these, they are for locking joints in position, when moving other joints. IK or INVERSE KINEMATICS works from the top of the Hierarchy down, sometimes it can do funny thinks, avoided by using ANCHORS on certain joints. Any discoveries about these tools would be appreciated - email them to: realsoft@tidalsound.com

Well there you have it. This is the process I went through when creating a Skeleton for Character Animation.

I WOULD RECOMMEND THAT YOU SAVE YOUR SKELETON AT IMPORTANT STAGES ALONG THE WAY. SAVE AT PRE ATTACHING AND PRE DUPLICATION FOR EXAMPLE. USE DIFFERENT MEANINGFUL FILE NAMES FOR EACH STAGE. IF YOU SCREW UP YOU CAN ALWAYS REVERT BACK TO THE PREVIOUS SAVED FILE.

BEFORE DOING THE FOLLOWING SAVE AGAIN AS DIFFERENT NAME.

Animating the Sub Skeletons is easy enough. All one has to do is select the SPINE SKELETON and go into EDIT MODE. This will allow you to select and move all the joints in the whole Hierarchical Skeleton. Using KEY FRAME Animation you can, for example, press RECORD at FRAME 20, select the left arm, go into edit mode, select the Joint [ Red Dot ] at the top of the arm and swing the whole arm forward using the technique described above [ to review click here ]. Unselect Record, go back to frame 0 and press play. Moving Skeleton!

The next tutorial will be ATTACHING the WHOLE SKELETON to the CHARACTER MESH, then animating our Character. Once I have ironed out the process and got over any pitfalls I will post that tutorial.

Meanwhile, fire ahead and build your Skeletons. Any things I have omitted, any glaring bluppers - please, as I said earlier, email me at: realsoft@tidalsound.com I appreciate your input as I, like you, am still learning also.

AIDAN O DRISCOLL - 10/2004





click here for top of page


Back to PART ONE of this tutorial >>