Rotation offset

I am not sure I understand the logic behind wanting to change the origin of your model via code, if you use blender just move your model in edit mode and you change its origin, its as simple as that.

Example: Your origin will most likely always be the center point of your models bounding box, in the case of a door just go into edit mode select all faces and move your model on its "x" axis until your origin point is at the edge of your door. Go back in in object mode and export to maratis. Now your door will rotate on the z axis as if it was on hinges.

Even is cases where the origin of your model might change to different locations you would ether load a new model or just animate this behavior.

But doing this in code if not done right can mess all kinds of things up "Motion, Physics, Collision Detection"

I don't have a code specific solution for you as this isn't something I tend to see people wanting to do on purpose, but maybe the above suggestion might help?

Last edited by zester (2013-10-14 23:51:56)

A blender (Mesh) importer wouldn't be that hard to write, provided you had experience writing blender plugins.  The (mesh) format is just simple xml.

I couldn't find any reference or detected changes to my two (mesh) files when I made changes to my cubes origin. You might want to put in a feature request for an addition to ...

<BoundingBox minx="-1.000000" miny="-1.000001" minz="-1.000000" maxx="1.000000" maxy="1.000000" maxz="1.000000" />

Such as ...

<BoundingBox ...>
    <Origin x="" y="" z=""/>
</BoundingBox>

That reminds me we need an xml binding for lua.

I appreciate your help attempts, but please now don't go off-topic. ^ ^

I know my stuff, I need to edit the mesh via code because I'm trying to do complex things and so the mesh must be manipulated by my game and not manually using Blender or other tools.
If you can find what's wrong in my above code, then post.
Thanks.

With "I know my stuff" I just meant that I know that you can change the origin in Blender but I really needed to change it via code. I just meant that, sorry if it sounded snob. Since you said "I am not sure I understand the logic behind..." I was just trying to say "yeah just trust me" lol.

Thanks for the input.
But I think that the pivot does exist.
I'll try to give more information, I just didn't want the first post to be a wall of text, but I guess it's necessary.
What I'm trying to do is to create a complex ragdoll which loads a mesh as the bounding box for every part.
What I'm doing is this:

say you have a forearm and two bones, elbow and wrist
create a ragdoll part
set its origin the same as the wrist bone
set the part position in the position the same as the wrist bone
set the pivot constraint = position of elbow bone
update the skeleton to match the rotation of the ragdoll part
start the physics context and enjoy how everything is working fine and the forearm swings

but problem: if your ragdoll part mesh which is the forearm is a bit rotated (in the mesh file), then your skeleton will rotate wrong. This is why I'm trying to add an offset rotation to its rotation.
If you now look at the code in the first post, you will see that it makes more sense, given that point P is the elbow bone position and point Q is the wrist bone position.

An alternative is rotating the mesh itself, but this seems even harder because you have to change normals too, etc., but I may look into that too.

Last edited by 255 (2013-10-15 16:40:10)

I mean your pivot exist just not ... never-mind doesn't matter.

You should have just said "Ragdoll, Code, Not Working, HELP" lol

I now see what your saying. Both solutions are incorrect thou, you wouldn't want to do ether. You do know that when you start messing with the pivot point your bounding box for each object modified is going to change its scale and transformation right?

Thats why I was say no no no no don't do that. Cause it will really mess with your physics. And then your ragdoll will really look bad.

Normally you wouldn't even use a ragdoll in a game, they exist for the purpose of recording a keyframed animation in your 3d package(blender) allowing you to simulate the physics of beating the crap out of a character to play back at a later time.

What you want doesn't have lua bindings yet "MArmature" and "MSkinData" I think "MSkinPoint * m_points;" is the  Bone's Transformation Matrice. If so thats what you would be wanting to tweek I do believe.

How is your C++? I would say put in a request.

I am half tempted to just re-implement the lua bindings using luabind would only take a couple of hours to wrap maratis entire codebase.

Last edited by zester (2013-10-15 17:22:23)

Not when you use the collision shape convex-hull.

You should more carefully read my posts BTW. You missed this important part:

start the physics context and enjoy how everything is working fine and the forearm swings

Which, in other words, means that my ragdoll code WORKS.
The problem is only when the mesh is a bit rotated (not facing the axis perfectly).
If I use a forearm mesh correctly rotated then my code does work. But I want my game to be able to accept and adapt to any meshes.

You are again forcing me to say "I know my stuff". I can't write yet another wall of text just to explain all my project goals. This topic is just to ask specific help on a very specific task.

Again, you have not read my posts carefully, since it's obvious that I'm using C++ and nothing else, with MArmature, MBones, etc.
This time you missed another line:

update the skeleton to match the rotation of the ragdoll part

Last edited by 255 (2013-10-15 18:06:12)

The code I've posted is not LUA, it's C++.

Sure, I didn't get mad, I was just pointing out what you were not understanding. The lua-code-misinterpretation makes everything clear now. It's just hard to show our mood via forum text, but you can stay assured that my mood is always quiet and calm.

I've tried using local points but no luck.
What kind of values does setAxisAngleRotation() expects for the angle? e.g. float from 0 to 359
Just to know if I have the angle right.

Yes, reading the source file that you've posted I noticed RAD_TO_DEG.

Nice to know. What I'm trying to do is explained here: http://forum.maratis3d.com/viewtopic.php?pid=5545#p5545
Since the mesh file may have a mesh a bit rotated (not perfectly looking towards one of the axis), I need to adjust that.
How can I do it?
1) rotating the mesh itself editing the vertices
or
2) adding a rotation offset to the bone associated with the ragdoll part (what I'm currently trying to do).

My code for finding the offset is now the following. It only runs one time, at the ragdoll creation, and saves the offset data in a class which manages the ragdoll part (the forearm in this case).

//find the angle between the elbow and the wrist bones (I've tried both local and relative coordinates)
    MVector3 AxisYPoint = elbowBonePos;
    AxisYPoint.y = 1000;
    MVector3 A = AxisYPoint - elbowBonePos;  //vector A
    MVector3 B = wristBonePos - elbowBonePos;               //vector B
    A.normalize();
    B.normalize();

//find the angle
    float dp = A.dotProduct(B);
    float angle = acos(dp);

//find the sign of the angle
    MVector3 cross = B.crossProduct(A);
    if(B.dotProduct(cross) < 0)
        angle = -angle;

    ragdollPart->angle = float(angle * RAD_TO_DEG);
//find the axis
    ragdollPart->axis = cross;

The code for moving the bone is the following one (the first part is basically the code you gave me in another topic):

            //rotate the bone
            MMatrix4x4 myMatrix = character_using_the_ragdoll->getMatrix()->getInverse() * (*ragdollPart->entity->getMatrix());
            MObject3d * parentBone = bone->getParent();
            if(parentBone)
            {    //calculate object matrix in parentBone's space coordinate
                myMatrix = parentBone->getMatrix()->getInverse() * myMatrix;
            }
            //get rotation coords from myMatrix
            bone->setEulerRotation(myMatrix.getEulerAngles());


            //add offset (that I calculated before)
            bone->addAxisAngleRotation(ragdollPart->offsetAxis,ragdollPart->offsetAngle);

There is a lot of code of course that I'm not showing, where I set the physics properties and do other things, but everything is working. If I don't do this "offset thing" all the ragdoll is working fine and the arm is swinging around the pivot and the skeleton is correctly updated, but the skeleton forearm is slightly off in respect to the ragdoll part forearm, and this is what I was trying to solve.

Last edited by 255 (2013-10-16 13:35:01)