OpenGL ES(18): 核心:自定義EGL環境
1.簡介
EGL:
是OpenGL ES和本地視窗系統的介面,不同平臺上EGL配置是不一樣的,而
OpenGL的呼叫方式是一致的,就是說:OpenGL跨平臺就是依賴於EGL介面。
為什麼要自己建立EGL環境?
當我們需要把同一個場景渲染到不同的Surface上時,此時系統GLSurfaceView
就不能滿足需求了,所以我們需要自己建立EGL環境來實現渲染操作。
注意:OpenGL整體是一個狀態機,通過改變狀態就能改變後續的渲染方式,而
EGLContext(EgL上下文)就儲存有所有狀態,因此可以通過共享EGLContext
來實現同一場景渲染到不同的Surface上。
步驟:
1、得到Egl例項:
mEgl = (EGL10) EGLContext.getEGL();
2、得到預設的顯示裝置(就是視窗)
mEglDisplay = mEgl.eglGetDisplay(EGL10.EGL_DEFAULT_DISPLAY);
if (mEglDisplay == EGL10.EGL_NO_DISPLAY){
throw new RuntimeException("eglGetDisplay failed");
}
3、初始化預設顯示裝置
int[] version = new int[2]; if (!mEgl.eglInitialize(mEglDisplay,version)){ throw new RuntimeException("eglInitialize failed"); } //version中存放EGL 版本號,int[0]為主版本號,int[1]為子版本號
4、設定顯示裝置的屬性,根據設定的屬性尋找相匹配的配置的個數
int[] attrbutes = new int[]{ EGL10.EGL_RED_SIZE,8, EGL10.EGL_GREEN_SIZE,8, EGL10.EGL_BLUE_SIZE,8, EGL10.EGL_ALPHA_SIZE,8, EGL10.EGL_DEPTH_SIZE,8, EGL10.EGL_STENCIL_SIZE,8, EGL10.EGL_RENDERABLE_TYPE,4, EGL10.EGL_NONE }; int[] num_config = new int[1]; if (!mEgl.eglChooseConfig(mEglDisplay,attrbutes,null,1,num_config)){ throw new IllegalArgumentException("eglChooseConfig failes"); } int numConfigs = num_config[0]; if (numConfigs <= 0){ throw new IllegalArgumentException("No configs match configSpec"); } //eglChooseConfig()引數解釋: //null,1 表示找到了配置不存放,表示只找一個匹配的配置就行了 //num_config[0] 用於存放匹配的配置的個數,如果連一個也找不到,那就是沒有。
5、從系統中獲取對應屬性的配置,(如果對應的配置數大於0)
EGLConfig[] configs = new EGLConfig[numConfigs];
if (!mEgl.eglChooseConfig(mEglDisplay,attrbutes,configs,numConfigs,num_config)){
throw new IllegalArgumentException("eglChooseConfig get failed");
}
//這裡用EGLConfig[] 存放相匹配的配置
6、建立EglContext
※ 需要用EGLDisPlay和對應的配置外加eglContext 來 建立EGLContext
if (eglContext != null){
mEglContext = mEgl.eglCreateContext(mEglDisplay,configs[0],eglContext,null);
}else {
mEglContext = mEgl.eglCreateContext(mEglDisplay,configs[0],EGL10.EGL_NO_CONTEXT,null);
}
//eglCreateContext()引數解釋:
//由於傳入的 eglContext == null ,所以需要傳入 EGL10.EGL_NO_CONTEXT
//如果傳入的 eglContext != null ,就傳入 eglContext
7、建立渲染的Surface
※ 需要用EGLDisPlay和對應的配置外加surface 來 建立EGLSurface
surface可以由SurfaceView的SurfaceHolder來得到。
mEglSurface = mEgl.eglCreateWindowSurface(mEglDisplay,configs[0],surface,null);
8、繫結EglContext和Surface到顯示裝置中
if (!mEgl.eglMakeCurrent(mEglDisplay,mEglSurface,mEglSurface,mEglContext)){
throw new RuntimeException("eglMakeCurrent fail");
}
9、重新整理資料,顯示渲染場景
if (mEgl != null){
return mEgl.eglSwapBuffers(mEglDisplay,mEglSurface);
}else {
throw new RuntimeException("egl is null");
}
GLSurfaceView原始碼中三個重要的類的分析:之後的自定義都是借鑑原始碼
GLThread:OpenGL ES的執行執行緒。包含建立EGL環境、呼叫GLRender的onSurfaceCreated、onSurfaceChanged和onDrawFrame方法以及生命週期的管理。繪製需要線上程中。
EglHelper:負責建立EGL環境。
GLSurfaceView:負責提供Surface和狀態改變。
2.自定義EglHelper 示例程式碼如下
EglHelper.java
import android.view.Surface;
import javax.microedition.khronos.egl.EGL10;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.egl.EGLContext;
import javax.microedition.khronos.egl.EGLDisplay;
import javax.microedition.khronos.egl.EGLSurface;
public class EglHelper {
private EGL10 mEgl;
private EGLDisplay mEglDisplay;
private EGLContext mEglContext;
private EGLSurface mEglSurface;
public void initEgl(Surface surface , EGLContext eglContext){
mEgl = (EGL10) EGLContext.getEGL();
mEglDisplay = mEgl.eglGetDisplay(EGL10.EGL_DEFAULT_DISPLAY);
if (mEglDisplay == EGL10.EGL_NO_DISPLAY){
throw new RuntimeException("eglGetDisplay failed");
}
int[] version = new int[2];
if (!mEgl.eglInitialize(mEglDisplay,version)){
throw new RuntimeException("eglInitialize failed");
}
int[] attrbutes = new int[]{
EGL10.EGL_RED_SIZE,8,
EGL10.EGL_GREEN_SIZE,8,
EGL10.EGL_BLUE_SIZE,8,
EGL10.EGL_ALPHA_SIZE,8,
EGL10.EGL_DEPTH_SIZE,8,
EGL10.EGL_STENCIL_SIZE,8,
EGL10.EGL_RENDERABLE_TYPE,4,
EGL10.EGL_NONE
};
int[] num_config = new int[1];
if (!mEgl.eglChooseConfig(mEglDisplay,attrbutes,null,1,num_config)){
throw new IllegalArgumentException("eglChooseConfig failes");
}
int numConfigs = num_config[0];
if (numConfigs <= 0){
throw new IllegalArgumentException("No configs match configSpec");
}
EGLConfig[] configs = new EGLConfig[numConfigs];
if (!mEgl.eglChooseConfig(mEglDisplay,attrbutes,configs,numConfigs,num_config)){
throw new IllegalArgumentException("eglChooseConfig get failed");
}
if (eglContext != null){
mEglContext = mEgl.eglCreateContext(mEglDisplay,configs[0],eglContext,null);
}else {
mEglContext = mEgl.eglCreateContext(mEglDisplay,configs[0],EGL10.EGL_NO_CONTEXT,null);
}
mEglSurface = mEgl.eglCreateWindowSurface(mEglDisplay,configs[0],surface,null);
if (!mEgl.eglMakeCurrent(mEglDisplay,mEglSurface,mEglSurface,mEglContext)){
throw new RuntimeException("eglMakeCurrent fail");
}
}
public EGLContext getmEglContext(){
return mEglContext;
}
public boolean swapBuffers(){
if (mEgl != null){
return mEgl.eglSwapBuffers(mEglDisplay,mEglSurface);
}else {
throw new RuntimeException("egl is null");
}
}
public void destoryEgl(){
if (mEgl != null){
mEgl.eglMakeCurrent(mEglDisplay,
EGL10.EGL_NO_SURFACE,
EGL10.EGL_NO_SURFACE,
EGL10.EGL_NO_CONTEXT
);
mEgl.eglDestroySurface(mEglDisplay,mEglSurface);
mEglSurface = null;
mEgl.eglDestroyContext(mEglDisplay,mEglContext);
mEglContext = null;
mEgl.eglTerminate(mEglDisplay);
mEglDisplay = null;
mEgl = null;
}
}
}
使用自定義的EGL環境如下:
import android.opengl.GLES20;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class MainActivity extends AppCompatActivity {
private SurfaceView surfaceView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
surfaceView = (SurfaceView) findViewById(R.id.mysurfaceView);
surfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
}
@Override
public void surfaceChanged(final SurfaceHolder holder, int format, final int width, final int height) {
new Thread(){
@Override
public void run() {
super.run();
//建立EGL環境
EglHelper eglHelper = new EglHelper();
eglHelper.initEgl(holder.getSurface(), null);
while(true)
{
GLES20.glViewport(0, 0, width, height);
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
GLES20.glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
eglHelper.swapBuffers();
try {
Thread.sleep(16);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
//egl.destroy
}
});
}
}
效果: