Android(安卓)renderscript, more info' and an example application

Here's a few more snippets of information I've managed to uncover on android renderscript:

* Compiled on the device
* Uses acc compiler
* No architectural support issues.
* No external libraries
* You cannot #include
* No allocation allowed
* Safe predictable

I admit some of these statements don't give too much away, but there's not too much else to go on at the moment. It does seem to point to a language that is compiled and is C like, but maybe with not all the power of C as allocations are not allowed.

Trying to shed some more light on things I had another look in the source code and found a few simple example Android applications usingrenderscript One of these simple example applications was called Fountain , it seemed to be one of the simplest applications so i thought it would be a good place to start.

The Android Fountain renderscript example

What does this application do? Well I'm not totally sure because i haven't run it myself, and to be honest there are not many comments in the code, so it really is a case of read the code and work it out. My best guess is that it produces a Fountain like animation that randomly animates points on a screen generally moving up and outwards in a fountain like way. These animations start when a users touches the screen and originate from that point. This is my best guess at the moment from what I can make out in the code example.

OK so what does the code look like?. First lets have a look at the files and how they are layed out, the structure is :

* Android.mk
* AndroidManifest.xml
* res
o drawable
+ gadgets_clock_mp3.png
o raw
+ fountain.c
* src
o com
+ android
# fountain
# Fountain.java
# FountainRS.java
# FountainView.java

Most of what we see here is a standard looking Android application. We have the basic android files such as the AndroidManifest file. Then we have our src directory that contains our android application source files, also we have the res directory, not unsual as it contains the drawable and raw directories, but as you can see the raw directory contains one very interesting and rather unusual file, the fountain.c file. This, it seems, is where therenderscript code resides, and the name does indeed suggest that it is C code file. So lets have a look at what is contained in this file:

view sourceprint?

01// Fountain test script02#pragma version(1)03 04int newPart = 0;05 06int main(int launchID) {07    int ct;08    int count = Control->count;09    int rate = Control->rate;10    float height = getHeight();11    struct point_s * p = (struct point_s *)point;12 13    if (rate) {14        float rMax = ((float)rate) * 0.005f;15        int x = Control->x;16        int y = Control->y;17        char r = Control->r * 255.f;18        char g = Control->g * 255.f;19        char b = Control->b * 255.f;20        struct point_s * np = &p[newPart];21 22        while (rate--) {23            vec2Rand((float *)np, rMax);24            np->x = x;25            np->y = y;26            np->r = r;27            np->g = g;28            np->b = b;29            np->a = 0xf0;30            newPart++;31            np++;32            if (newPart >= count) {33                newPart = 0;34                np = &p[newPart];35            }36        }37    }38 39    for (ct=0; ct < count; ct++) {40        float dy = p->dy + 0.15f;41        float posy = p->y + dy;42        if ((posy > height) && (dy > 0)) {43            dy *= -0.3f;44        }45        p->dy = dy;46        p->x += p->dx;47        p->y = posy;48        p++;49    }50 51    uploadToBufferObject(NAMED_PartBuffer);52    drawSimpleMesh(NAMED_PartMesh);53    return 1;54} Yes, it is very C like. We have structs, pointers and chars. Starting at the top of the file. We have a Control structure or class that gives use a rate and a count as well as x,y and r,g,b values. Where does this Control structure get instantiated? I'll come back to this. Another structure that is also used in this code is point_s. This structure has a x and y coordinates, r,g,b values, which are likely to be Red, blue green, and an "a" value which is the alpha value. Without more information I cannot be sure exactly what is happening in this code, but I think that generally an array of points is given and then array of new points is generated, to allow some kind of animation.Looking at the src code directory we have three .java files. Fountain.java, FountainView.java and FountainRS.java. Fountain.java is just the basic Android activity class that has an onCreate method that sets the contentView to an instance of FountainView. The Code for the FountainView.java file looks like this:view sourceprint?01/*02 * Copyright (C) 2008 The Android Open Source Project03 *04 * Licensed under the Apache License, Version 2.0 (the "License");05 * you may not use this file except in compliance with the License.06 * You may obtain a copy of the License at07 *08 *      http://www.apache.org/licenses/LICENSE-2.009 *10 * Unless required by applicable law or agreed to in writing, software11 * distributed under the License is distributed on an "AS IS" BASIS,12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.13 * See the License for the specific language governing permissions and14 * limitations under the License.15 */16 17package com.android.fountain;18 19import java.io.Writer;20import java.util.ArrayList;21import java.util.concurrent.Semaphore;22 23import android.renderscript.RSSurfaceView;24import android.renderscript.RenderScript;25 26import android.content.Context;27import android.content.res.Resources;28import android.graphics.Bitmap;29import android.graphics.drawable.BitmapDrawable;30import android.graphics.drawable.Drawable;31import android.os.Handler;32import android.os.Message;33import android.util.AttributeSet;34import android.util.Log;35import android.view.Surface;36import android.view.SurfaceHolder;37import android.view.SurfaceView;38import android.view.KeyEvent;39import android.view.MotionEvent;40 41public class FountainView extends RSSurfaceView {42 43    public FountainView(Context context) {44        super(context);45        //setFocusable(true);46    }47 48    private RenderScript mRS;49    private FountainRS mRender;50 51    private void destroyRS() {52        if(mRS != null) {53            mRS = null;54            destroyRenderScript();55        }56        java.lang.System.gc();57    }58 59    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {60        super.surfaceChanged(holder, format, w, h);61        destroyRS();62        mRS = createRenderScript(false, true);63        mRender = new FountainRS();64        mRender.init(mRS, getResources(), w, h);65    }66 67    public void surfaceDestroyed(SurfaceHolder holder) {68        // Surface will be destroyed when we return69        destroyRS();70    }71 72 73 74    @Override75    public boolean onTouchEvent(MotionEvent ev)76    {77        int act = ev.getAction();78        if (act == ev.ACTION_UP) {79            mRender.newTouchPosition(0, 0, 0);80            return false;81        }82        float rate = (ev.getPressure() * 50.f);83        rate *= rate;84        if(rate > 2000.f) {85            rate = 2000.f;86        }87        mRender.newTouchPosition((int)ev.getX(), (int)ev.getY(), (int)rate);88        return true;89    }90}

The FountainView class is an Android View. As you can see from the code, FountainView extends a new type of Android view RSSufraceView. It also has references to a new RenderScript class and our defined FountainRS class. When creating a new surface in the surfacedChanged method a new RenderScript class and a new FountainRS class are created. We also call the init method on the FountainRS class and pass in several arguments, including a reference to the RenderScript object. So lets have a look at the FountainRS.java file:
view sourceprint?

001/*002 * Copyright (C) 2008 The Android Open Source Project003 *004 * Licensed under the Apache License, Version 2.0 (the "License");005 * you may not use this file except in compliance with the License.006 * You may obtain a copy of the License at007 *008 *      http://www.apache.org/licenses/LICENSE-2.0009 *010 * Unless required by applicable law or agreed to in writing, software011 * distributed under the License is distributed on an "AS IS" BASIS,012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.013 * See the License for the specific language governing permissions and014 * limitations under the License.015 */016 017package com.android.fountain;018 019import android.content.res.Resources;020import android.renderscript.*;021import android.util.Log;022 023 024public class FountainRS {025    public static final int PART_COUNT = 20000;026 027    static class SomeData {028        public int x;029        public int y;030        public int rate;031        public int count;032        public float r;033        public float g;034        public float b;035    }036 037    public FountainRS() {038    }039 040    public void init(RenderScript rs, Resources res, int width, int height) {041        mRS = rs;042        mRes = res;043        initRS();044    }045 046    public void newTouchPosition(int x, int y, int rate) {047        if (mSD.rate == 0) {048            mSD.r = ((x & 0x1) != 0) ? 0.f : 1.f;049            mSD.g = ((x & 0x2) != 0) ? 0.f : 1.f;050            mSD.b = ((x & 0x4) != 0) ? 0.f : 1.f;051            if ((mSD.r + mSD.g + mSD.b) < 0.9f) {052                mSD.r = 0.8f;053                mSD.g = 0.5f;054                mSD.b = 1.f;055            }056        }057        mSD.rate = rate;058        mSD.x = x;059        mSD.y = y;060        mIntAlloc.data(mSD);061    }062 063 064    /////////////////////////////////////////065 066    private Resources mRes;067 068    private RenderScript mRS;069    private Allocation mIntAlloc;070    private SimpleMesh mSM;071    private SomeData mSD;072    private Type mSDType;073 074    private void initRS() {075        mSD = new SomeData();076        mSDType = Type.createFromClass(mRS, SomeData.class, 1, "SomeData");077        mIntAlloc = Allocation.createTyped(mRS, mSDType);078        mSD.count = PART_COUNT;079        mIntAlloc.data(mSD);080 081        Element.Builder eb = new Element.Builder(mRS);082        eb.addFloat(Element.DataKind.USER, "dx");083        eb.addFloat(Element.DataKind.USER, "dy");084        eb.addFloatXY("");085        eb.addUNorm8RGBA("");086        Element primElement = eb.create();087 088 089        SimpleMesh.Builder smb = new SimpleMesh.Builder(mRS);090        int vtxSlot = smb.addVertexType(primElement, PART_COUNT);091        smb.setPrimitive(Primitive.POINT);092        mSM = smb.create();093        mSM.setName("PartMesh");094 095        Allocation partAlloc = mSM.createVertexAllocation(vtxSlot);096        partAlloc.setName("PartBuffer");097        mSM.bindVertexAllocation(partAlloc, 0);098 099        // All setup of named objects should be done by this point100        // because we are about to compile the script.101        ScriptC.Builder sb = new ScriptC.Builder(mRS);102        sb.setScript(mRes, R.raw.fountain);103        sb.setRoot(true);104        sb.setType(mSDType, "Control", 0);105        sb.setType(mSM.getVertexType(0), "point", 1);106        Script script = sb.create();107        script.setClearColor(0.0f, 0.0f, 0.0f, 1.0f);108 109        script.bindAllocation(mIntAlloc, 0);110        script.bindAllocation(partAlloc, 1);111        mRS.contextBindRootScript(script);112    }113 114}

I'm not going to try and go through every detail of this code, but it seems that the interesting areas are in the initRS function. Here we have element builders, Simple Mesh builders and last but not least a script builder. Here we get a script builder instance, set the script to the fountain.c file. Set up some types such as Control and point (remember, these were used in the fountain.c file) and then create the script.

So there we have it, this is a quick peek into how Renderscript might be used. There are still a lot of unanswered questions yet, and there is still a lot more to learn about how renderscript will, and can be use, but i hope these few code snippets will at least give people a starting point. As usual, if anyone else out there has any interesting insights or comments I'd be really interested to hear them.

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