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Rotation.java
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package nz.gen.geek_central.GLUseful;
/*
Quaternion representation of 3D rotation transformations.
Copyright 2011, 2013 by Lawrence D'Oliveiro <ldo@geek-central.gen.nz>.
Licensed under the Apache License, Version 2.0 (the "License"); you may not
use this file except in compliance with the License. You may obtain a copy of
the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
License for the specific language governing permissions and limitations under
the License.
*/
import static nz.gen.geek_central.GLUseful.GLUseful.gl;
public class Rotation implements android.os.Parcelable
{
public final float c, s; /* cosine and sine of half the rotation angle */
public final float x, y, z; /* rotation axis unit vector */
/* actually quaternion is (c, s * x, s * y, s * z) */
public Rotation
(
float Angle,
boolean Degrees, /* false for radians */
float X,
float Y,
float Z
)
/* constructs a Rotation that rotates by the specified angle
about the axis direction (X, Y, Z). */
{
final double Theta = Float.isNaN(Angle) ? 0.0 : (Degrees ? Math.toRadians(Angle) : Angle) / 2;
c = (float)Math.cos(Theta);
s = (float)Math.sin(Theta);
final float Mag = (float)Math.sqrt(X * X + Y * Y + Z * Z);
x = X / Mag;
y = Y / Mag;
z = Z / Mag;
} /*Rotation*/
public Rotation
(
float Angle,
boolean Degrees, /* false for radians */
Vec3f Axis
)
{
this(Angle, Degrees, Axis.x, Axis.y, Axis.z);
} /*Rotation*/
public static final Rotation Null = new Rotation(0, 0, 0, 1);
/* represents no rotation at all */
private Rotation
(
float c,
float x,
float y,
float z
)
/* internal-use constructor with directly-computed components. Note
this does not compensate for accumulated rounding errors. */
{
this.c = c;
this.s = (float)Math.sqrt(x * x + y * y + z * z);
this.x = x / this.s;
this.y = y / this.s;
this.z = z / this.s;
} /*Rotation*/
private Rotation
(
float c,
float s,
float x,
float y,
float z
)
/* internal-use constructor with directly-computed components. Note
this does not compensate for accumulated rounding errors. */
{
this.c = c;
this.s = s;
this.x = x;
this.y = y;
this.z = z;
} /*Rotation*/
public static final android.os.Parcelable.Creator<Rotation> CREATOR =
/* restore state from a Parcel. */
new android.os.Parcelable.Creator<Rotation>()
{
public Rotation createFromParcel
(
android.os.Parcel Post
)
{
final android.os.Bundle MyState = Post.readBundle();
return
new Rotation
(
MyState.getFloat("c", Null.c),
MyState.getFloat("s", Null.s),
MyState.getFloat("x", Null.x),
MyState.getFloat("y", Null.y),
MyState.getFloat("z", Null.z)
);
} /*createFromParcel*/
public Rotation[] newArray
(
int NrElts
)
{
return
new Rotation[NrElts];
} /*newArray*/
} /*Parcelable.Creator*/;
@Override
public int describeContents()
{
return
0; /* nothing special */
} /*describeContents*/
@Override
public void writeToParcel
(
android.os.Parcel Post,
int Flags
)
/* save state to a Parcel. */
{
final android.os.Bundle MyState = new android.os.Bundle();
MyState.putFloat("c", c);
MyState.putFloat("s", s);
MyState.putFloat("x", x);
MyState.putFloat("y", y);
MyState.putFloat("z", z);
Post.writeBundle(MyState);
} /*writeToParcel*/
public Rotation inv()
/* returns rotation by the opposite angle around the same axis. Or alternatively,
the same angle around the opposite-pointing axis . */
{
return
new Rotation(c, -s, x, y, z);
} /*inv*/
public Rotation mul
(
Rotation that
)
/* returns composition with another rotation. */
{
final float s2 = this.s * that.s;
return
new Rotation
(
this.c * that.c - (this.x * that.x + this.y * that.y + this.z * that.z) * s2,
(this.y * that.z - this.z * that.y) * s2 + this.c * that.x * that.s + that.c * this.x * this.s,
(this.z * that.x - this.x * that.z) * s2 + this.c * that.y * that.s + that.c * this.y * this.s,
(this.x * that.y - this.y * that.x) * s2 + this.c * that.z * that.s + that.c * this.z * this.s
);
} /*mul*/
public Rotation div
(
Rotation that
)
/* returns the difference from another rotation. */
{
return
mul(that.inv());
} /*div*/
public Rotation mul
(
float Frac /* can also be negative or > 1 */
)
/* returns the specified fraction of the rotation. */
{
return
new Rotation
(
GetAngle(false) * Frac, false, x, y, z
);
} /*mul*/
public float GetAngle
(
boolean Degrees /* false for radians */
)
/* returns the rotation angle. */
{
final double Theta = Math.atan2(s, c);
return
2 * (float)(Degrees ? Math.toDegrees(Theta) : Theta);
} /*GetAngle*/
public Vec3f GetAxis()
{
return
new Vec3f(x, y, z);
} /*GetAxis*/
public void Apply()
/* applies the rotation to the currently-selected GL matrix. */
{
gl.glRotatef(GetAngle(true), x, y, z);
} /*Apply*/
public String toString()
{
return
String.format
(
GLUseful.StdLocale,
"Rotation(%e, %e, %e, %e, %e)",
c, s, x, y, z
);
} /*toString*/
} /*Rotation*/;