Techne Y Rotation Bug (Minecraft modeling program)

Question

Ok. First time here, but im running out of options. Hope you can help!

The problem is, in the program Techne, the rotation is a little glitchy. The X Y and Z all work fine, but if you try to do anything in combination (besides X and Z) it doesnt work. After lots of testing. I've concluded this. The Y doesnt take the local rotation of the object, only its beginning rotation point. To put it simpler, If i rotate an object along the Z axis any amount of degrees, lets say 40, Then the Y still thinks its at 0, and rotates accordingly. So lets say we're looking at the object in 3D, and we're looking straight at the XY axis, so we only see one face of a cube. If we rotate that Z 40 degrees, it rotates Clockwise 40 degrees. The problem is that when rotating the Y, Instead of rotating along the new Axis, it still rotates along the origin. So it rotates perfectly.....idk how to say this, Cylindrical. Instead of rotating Up and to the left, it just rotates to the left. After comparing techne to Blender, i've found that the problem is, for some reason, the Y will only rotate along its Delta. Now, im hopeless at math, and doubt i even got far enough into math to know half this stuff. So if i used any terms wrong, please comment and ask questions, CAUSE I NEED THIS ANSWERED.

Now, the whole reason im asking this, is because we can make our models all fine and dandy, but where the bug SHOWS is in the code. We export this models into java, and the Java does the rotations CORRECTLY. So now, our models are messed up, because the Y on some blocks isnt where our modellers though it would be.

So here's my question, What would i need to do, formula wise, java wise, anything! to get that bug to become "correct". So that what we see in techne, appears in minecraft, even though the Y is bugged.

Hope i explained well enough, if you need any further explaination, please comment!

Answer 1

Despite this being a super old post, I'm going to answer it because it's the fist hit on Google for "Techne rotations", etc. And I happened to run into the same issue. Just sorry I'm a few years too late.

So, the problem is that Techne is exporting the Euler angles (the X, Y, and Z angles) assuming a YZX order. What that means is, first the rotation around the Y axis is applied, then the rotation around the Z axis, then around the X axis. But Minecraft actually uses Euler angles in ZYX order. So basically the exported angles are wrong if you have any rotation around the Y axis.

To fix this, you need to convert from YZX ordered Euler angles to ZYX ordered Euler angles. This function I wrote should do the trick:

     private Vector3f ConvertEulerYzxToZyx(Vector3f eulerYzx) {
         // Create a matrix from YZX ordered Euler angles
         float a = MathHelper.cos(eulerYzx.x);
         float b = MathHelper.sin(eulerYzx.x);
         float c = MathHelper.cos(eulerYzx.y);
         float d = MathHelper.sin(eulerYzx.y);
         float e = MathHelper.cos(eulerYzx.z);
         float f = MathHelper.sin(eulerYzx.z);
         Matrix4f matrix = new Matrix4f();
         matrix.m00 = c * e;
         matrix.m01 = b * d - a * c * f;
         matrix.m02 = b * c * f + a * d;
         matrix.m10 = f;
         matrix.m11 = a * e;
         matrix.m12 = -b * e;
         matrix.m20 = -d * e;
         matrix.m21 = a * d * f + b * c;
         matrix.m22 = a * c - b * d * f;
         matrix.m33 = 1.0F;
         // Create ZYX ordered Euler angles from the matrix
         Vector3f eulerZyx = new Vector3f();
         eulerZyx.y = (float) Math.asin(MathHelper.clamp_float(-matrix.m20, -1, 1));
         if (MathHelper.abs(matrix.m20) < 0.99999) {
             eulerZyx.x = (float) Math.atan2(matrix.m21, matrix.m22);
             eulerZyx.z = (float) Math.atan2(matrix.m10, matrix.m00);
         } else {
             eulerZyx.x = 0.0F;
             eulerZyx.z = (float) Math.atan2(-matrix.m01, matrix.m11);
         }
         return eulerZyx;
     }

You can just convert the rotations as they're set:

     private void setRotationWithEulerYzx(ModelRenderer model, float x, float y, float z) {
         Vector3f eulerYzx = new Vector3f(x, y, z);
         Vector3f eulerZyx = ConvertEulerYzxToZyx(eulerYzx);
         model.rotateAngleX = eulerZyx.x;
         model.rotateAngleY = eulerZyx.y;
         model.rotateAngleZ = eulerZyx.z;
     }

Now just replace all the setRotation with setRotationWithEulerYzx, and your model will work.

Techne Y Rotation Bug (Minecraft modeling program)

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