CubeActivity.java

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/*
 * Copyright 2021 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
package org.skia.jetskidemo;
 
import android.app.Activity;
import android.content.res.Resources;
import android.os.Bundle;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.SurfaceView;
 
import org.skia.jetski.Canvas;
import org.skia.jetski.Matrix;
import org.skia.jetski.Surface;
import org.skia.jetski.util.SurfaceRenderer;
 
import org.skia.jetskidemo.samples.ImageShaderSample;
import org.skia.jetskidemo.samples.RuntimeSample;
import org.skia.jetskidemo.samples.Sample;
import org.skia.jetskidemo.samples.SkottieSample;
 
import static java.lang.Math.tan;
 
class Face {
    private float rotX;
    private float rotY;
    public Sample sample;
 
    Face(float rotX, float rotY, Sample sample) {
        this.rotX = rotX;
        this.rotY = rotY;
        this.sample = sample;
    }
 
    Matrix asMatrix(float scale) {
        return new Matrix().rotateY(rotY).rotateX(rotX).translate(0, 0, scale);
    }
}
 
// TODO: make this public?
class Vec3 {
    public float x, y, z;
 
    public Vec3(float x, float y, float z) { this.x = x; this.y = y; this.z = z; }
 
    public float length() { return (float)Math.sqrt(x*x + y*y + z*z); }
 
    public Vec3 normalize() {
        mul(1/length());
        return this;
    }
 
    public Vec3 add(float v) {
        x += v; y += v; z += v;
        return this;
    }
 
    public Vec3 mul(float v) {
        x *= v; y *= v; z *= v;
        return this;
    }
 
    public float dot(Vec3 v) {
        return x*v.x + y*v.y + z*v.z;
    }
 
    public Vec3 cross(Vec3 v) {
        float xx = y*v.z - z*v.y,
              yy = z*v.x - x*v.z,
              zz = x*v.y - y*v.x;
        x = xx; y = yy; z = zz;
        return this;
    }
};
 
class VSphereAnimator {
    private Matrix mRotMatrix = new Matrix();
    private Vec3   mRotAxis   = new Vec3(0, 1, 0),
                   mCurrentDrag;
    private float  mRotSpeed  = (float)Math.PI,
                   mCenterX,
                   mCenterY,
                   mRadius;
 
    public VSphereAnimator(float x, float y, float r) {
        mCenterX = x;
        mCenterY = y;
        mRadius  = r;
    }
 
    public void animate(float dt) {
        final float kDecay = 0.99f;
 
        rotate(mRotAxis, mRotSpeed * dt);
 
        mRotSpeed *= kDecay;
    }
 
    public Matrix getMatrix() {
        return mRotMatrix;
    }
 
    public void fling(float dx, float dy) {
        Vec3 u = normalVec(mCenterX, mCenterY),
             v = normalVec(mCenterX + dx, mCenterY + dy);
        mRotAxis = u.cross(v).normalize();
 
        double flingSpeed = Math.sqrt(dx*dx + dy*dy)/mRadius;
        mRotSpeed = (float)(flingSpeed*Math.PI);
    }
 
    public void startDrag(MotionEvent e) {
        mCurrentDrag = normalVec(e.getX(), e.getY());
        mRotSpeed = 0;
    }
 
    public void drag(MotionEvent e) {
        Vec3 u = mCurrentDrag,                  // previous drag position
             v = normalVec(e.getX(), e.getY()); // new drag position
 
        float angle = (float)Math.acos(Math.max(-1, Math.min(1, u.dot(v)/u.length()/v.length())));
        Vec3   axis = u.cross(v).normalize();
 
        rotate(axis, angle);
 
        mCurrentDrag = v;
    }
 
    private Vec3 normalVec(float x, float y) {
        x =  (x - mCenterX)/mRadius;
        y = -(y - mCenterY)/mRadius;
        float len2 = x*x + y*y;
 
        if (len2 > 1) {
            // normalize
            float len = (float)Math.sqrt(len2);
            x /= len;
            y /= len;
            len2 = 1;
        }
 
        return new Vec3(x, y, (float)Math.sqrt(1 - len2));
    }
 
    private void rotate(Vec3 axis, float angle) {
        mRotMatrix = new Matrix().rotate(axis.x, axis.y, axis.z, angle)
                                 .preConcat(mRotMatrix);
    }
};
 
class CubeRenderer extends SurfaceRenderer implements GestureDetector.OnGestureListener,
                                                      ScaleGestureDetector.OnScaleGestureListener {
    private VSphereAnimator mVSphere;
    private Matrix          mViewMatrix;
    private float           mCubeSideLength;
    private long            mPrevMS;
    private Face[]          mFaces;
    private float           mZoom = 1;
 
    public CubeRenderer(Resources res) {
        final float rot = (float) Math.PI;
        mFaces = new Face[] {
            new Face(0, -rot/2, new ImageShaderSample(res, R.raw.brickwork_texture)),
            new Face(0, 0     , new SkottieSample(res, R.raw.im_thirsty)),
            new Face(0, rot   , new RuntimeSample(res, R.raw.runtime_shader1)),
            new Face(rot/2, 0 , new SkottieSample(res, R.raw.permission)),
            new Face(0, rot/2 , new RuntimeSample(res, R.raw.runtime_shader2)),
        };
    }
 
    @Override
    protected void onSurfaceInitialized(Surface surface) {
        float cx = surface.getWidth()  / 2,
              cy = surface.getHeight() / 2,
              r  = Math.min(cx, cy);
 
        mVSphere = new VSphereAnimator(cx, cy, r);
 
        // square viewport size fitting the given surface
        float vsz = r * 2;
 
        mCubeSideLength = vsz * 0.5f;
 
        float viewAngle = (float)Math.PI / 4f,
              viewDistance = (float)(r / tan(viewAngle/2));
 
        mViewMatrix = new Matrix()
                        // centered viewport
                        .translate(cx, cy)
                        // perspective
                        .scale(vsz/2, vsz/2, 1)
                        .preConcat(Matrix.makePerspective(0.05f, viewDistance, viewAngle))
                        // camera
                        .preConcat(Matrix.makeLookAt(0, 0, -viewDistance, 0, 0, 0, 0, 1, 0));
    }
 
    @Override
    protected void onRenderFrame(Canvas canvas, long ms) {
        if (mPrevMS == 0) {
            mPrevMS = ms;
        }
 
        mVSphere.animate((ms - mPrevMS) / 1000.f);
        mPrevMS = ms;
 
 
        // clear canvas
        canvas.drawColor(0xffffffff);
 
        canvas.save();
        canvas.concat(mViewMatrix);
        canvas.scale(mZoom, mZoom);
        canvas.concat(mVSphere.getMatrix());
 
        drawFaces(canvas, ms, false);
        drawFaces(canvas, ms, true);
 
        canvas.restore();
    }
 
    private void drawFaces(Canvas canvas, long ms, boolean renderFront) {
        for (Face f : mFaces) {
            canvas.save();
            canvas.concat(f.asMatrix(mCubeSideLength/2));
 
            if (front(canvas.getLocalToDevice()) == renderFront) {
                f.sample.render(canvas, ms,
                                -mCubeSideLength/2,
                                -mCubeSideLength/2,
                                 mCubeSideLength/2,
                                 mCubeSideLength/2);
            }
            canvas.restore();
        }
    }
 
    private void zoom(float z) {
        final float kMinZoom = 0.5f,
                    kMaxZoom = 3.0f;
        mZoom = Math.max(kMinZoom, Math.min(kMaxZoom, mZoom * z));
    }
 
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float dx, float dy) {
        mVSphere.fling(dx, dy);
        return true;
    }
 
    @Override
    public boolean onDown(MotionEvent e) {
        mVSphere.startDrag(e);
        return true;
    }
 
    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float dx, float dy) {
        mVSphere.drag(e2);
        return true;
    }
 
    // GestureDetector stubs
    @Override
    public boolean onSingleTapUp(MotionEvent e) { return false; }
 
    @Override
    public void onLongPress(MotionEvent e) {}
 
    @Override
    public void onShowPress(MotionEvent e) {}
 
    private boolean front(Matrix m) {
        Matrix m2;
        try {
            m2 = Matrix.makeInverse(m);
        } catch (RuntimeException e) {
            m2 = new Matrix();
        }
        return m2.getAtRowCol(2, 2) > 0;
    }
 
    // OnScaleGestureListener
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        zoom(detector.getScaleFactor());
        return true;
    }
 
    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector) {
        zoom(detector.getScaleFactor());
        return true;
    }
 
    @Override
    public void onScaleEnd(ScaleGestureDetector detector) {
        zoom(detector.getScaleFactor());
    }
}
 
public class CubeActivity extends Activity {
    static {
        System.loadLibrary("jetski");
    }
 
    private GestureDetector      mGestureDetector;
    private ScaleGestureDetector mScaleDetector;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cube);
 
        SurfaceView sv = findViewById(R.id.surfaceView);
 
        CubeRenderer renderer = new CubeRenderer(getResources());
        sv.getHolder().addCallback(renderer);
 
        mGestureDetector = new GestureDetector(this, renderer);
        mScaleDetector = new ScaleGestureDetector(this, renderer);
    }
 
    @Override
    public boolean onTouchEvent(MotionEvent e) {
        // always dispatch to both detectors
        mGestureDetector.onTouchEvent(e);
        mScaleDetector.onTouchEvent(e);
 
        return true;
    }
}