Question

所以，我试图制作一个基于OpenGL ES 2（Android）的简单3D引擎。首先（除了许多教程等），我逐步从developer.android.com tutorial复制粘贴的代码。一切都很好。然后我开始修改它。我改变了Mesh课程＆＃39;字段和构造函数，以便不预设顶点坐标，着色器代码，颜色和顶点数（所有代码都在问题的末尾）。将GL20Renderer类中的网格字段更改为private List<Mesh> meshs = new ArrayList<Mesh>();。创建用于添加和删除网格的功能。目前在我的代码中使用的唯一添加功能如下：

public void addMesh( Mesh meshToAdd ) {
  meshs.add( meshToAdd );
}

GL20Renderer.onDrawFrame（）中唯一的变化是那里的代码循环遍历网格列表并为每个网格调用Mesh.draw（）方法：

for( Mesh meshToDraw : meshs ) {
  meshToDraw.draw(scratch);
}

然后我尝试从GL20Renderer.onSurfaceCreated（）方法添加一个网格 - 它工作正常。从同一方法添加另一个网格 - 工作正常。然后我尝试从GL20Activity.onCreate（）方法添加网格（同时从GL20Renderer.onSurfaceCreated（）中删除相同的代码）：

float[] vertexCoords = { 0.0f, 0.622008459f, 0.0f, -0.5f, -0.311004243f, 0.0f, 0.5f, -0.311004243f, 0.0f };
int[] drawOrder = { 1, 2, 3 };
float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
String vertexShaderCode = "uniform mat4 uMVPMatrix;" + "attribute vec4 vPosition;" + "void main() {" + "  gl_Position = uMVPMatrix * vPosition;" + "}";
String fragmentShaderCode = "precision mediump float;" + "uniform vec4 vColor;" + "void main() {" + "  gl_FragColor = vColor;" + "}";
renderer.addMesh( new Mesh( 3, vertexCoords, drawOrder, 1, color, vertexShaderCode, fragmentShaderCode) );

网格被添加到网格列表中但由于某种原因没有显示（它的属性与教程的网格属性相同）。如果从GL20Activity.onCreate（）和Renderer.onSurfaceCreated（）添加网格物体 - 它们都不会显示，但它们仍然在网格列表上。然后我将onRendererInitialized（）方法添加到GL20Activity，这是从GL20Renderer.onCreate（）方法的最后调用的。 onRendererInited（）只是添加一个网格，并且只有在GL20Activity.onCreate（）中没有添加网格时才会显示它。问题是：如果从GL20Activity.onCreate（）方法添加网格，为什么不绘制网格？我试过改变顶点＆＃39;坐标所以它们不是问题的原因。我还尝试向GL20Renderer.onDrawFrame（）添加一些代码以确保meshToDraw.draw( scratch );代码行正常运行，并且它确实正常运行，但仍然没有绘制网格。但由于网格具有相同的顶点＆＃39;从GL20Activity.onRendererInitialized（）和/或GL20Renderer.onSurfaceCreated（）中添加的坐标和颜色被绘制，绘制网格不应该有任何问题，这是从GL20Activity.onCreate（）添加的。

MainActivity.java：

package com.Reaper.VisionEngine;
import android.app.*;
import android.content.*;
import android.os.*;

public class MainActivity extends Activity {

  @Override
  protected void onCreate(Bundle savedInstanceState {
    super.onCreate(savedInstanceState);
    Intent intent = new Intent( this, GL20Activity.class );
    startActivity( intent );
  }
}

GL20Activity.java：

package com.Reaper.VisionEngine;
import android.app.*;
import android.os.*;
import android.widget.*;
import com.Reaper.VisionEngine.GLRenderer.*;
import com.Reaper.VisionEngine.GLSurfaceView.*;
import com.Reaper.VisionEngine.Mesh.*;
import java.io.*;

public class GL20Activity extends Activity {
  GL20SurfaceView GLView;
  GL20Renderer renderer;

  @Override
  protected void onCreate( Bundle savedInstanceState ) {
    super.onCreate(savedInstanceState);
    GLView = new GL20SurfaceView(this);
    setContentView(GLView);
    renderer = GLView.getRenderer();
    float[] vertexCoords = { 0.0f, 0.622008459f, 0.0f, -0.5f, -0.311004243f, 0.0f, 0.5f, -0.311004243f, 0.0f };
    int[] drawOrder = { 1, 2, 3 };
    float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
    String vertexShaderCode = "uniform mat4 uMVPMatrix;" + "attribute vec4 vPosition;" + "void main() {" + "  gl_Position = uMVPMatrix * vPosition;" + "}";
    String fragmentShaderCode = "precision mediump float;" + "uniform vec4 vColor;" + "void main() {" + "  gl_FragColor = vColor;" + "}";
    renderer.addMesh( new Mesh( 3, vertexCoords, drawOrder, 1, color, vertexShaderCode, fragmentShaderCode) );
  }

GL20Renderer.java：

package com.Reaper.VisionEngine.GLRenderer;
import android.opengl.*;
import com.Reaper.VisionEngine.*;
import com.Reaper.VisionEngine.Mesh.*;
import java.util.*;
import javax.microedition.khronos.egl.*;
import javax.microedition.khronos.opengles.*;
import javax.microedition.khronos.egl.EGLConfig;

public class GL20Renderer implements GLSurfaceView.Renderer {
  private List<Mesh> meshs = new ArrayList<Mesh>();
  private final float[] mMVPMatrix = new float[16];
  private final float[] mProjectionMatrix = new float[16];
  private final float[] mViewMatrix = new float[16];
  private float[] mRotationMatrix = new float[16];
  public volatile float mAngle;
  private List<Mesh> meshQueue = new ArrayList<Mesh>();
  private GL20Activity activity;

  public void onSurfaceCreated(GL10 gl, EGLConfig glConfig) {
    GLES20.glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
  }

  public void onDrawFrame(GL10 gl) {
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
    Matrix.setLookAtM(mViewMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
    Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mViewMatrix, 0);
    float[] scratch = new float[16];
    Matrix.setRotateM(mRotationMatrix, 0, mAngle, 0, 0, -1.0f);
    Matrix.multiplyMM(scratch, 0, mMVPMatrix, 0, mRotationMatrix, 0);
    for( Mesh meshToDraw : meshs ) {
      meshToDraw.draw(scratch);
    }
  }

  public void onSurfaceChanged(GL10 gl, int width, int height) {
    GLES20.glViewport(0, 0, width, height);
    float ratio = (float) width / height;
    Matrix.frustumM(mProjectionMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
  }

  public static int loadShader(int type, String shaderCode){
    int shader = GLES20.glCreateShader(type);
    GLES20.glShaderSource(shader, shaderCode);
    GLES20.glCompileShader(shader);
    return shader;
  }

  public void addMesh( Mesh meshToAdd ) {
    meshs.add( meshToAdd );
  }

GL20SurfaceView.java：

package com.Reaper.VisionEngine.GLSurfaceView;
import android.content.*;
import android.opengl.*;
import android.view.*;
import com.Reaper.VisionEngine.*;
import com.Reaper.VisionEngine.GLRenderer.*;

public class GL20SurfaceView extends GLSurfaceView {
  private final GL20Renderer Renderer;

  public GL20SurfaceView(Context context) {
    super(context);
    setEGLContextClientVersion(2);
    Renderer = new GL20Renderer();
    setRenderer(Renderer);
    setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
  }

  public boolean onTouchEvent(MotionEvent e) { // TODO: CHANGE THIS
    switch (e.getAction()) {
      case MotionEvent.ACTION_MOVE:
      requestRender();
    }
    return true;
  }

  public GL20Renderer getRenderer() {
    return Renderer;
  }
}

Mesh.java：

package com.Reaper.VisionEngine.Mesh;
import android.opengl.*;
import com.Reaper.VisionEngine.GLRenderer.*;
import java.nio.*;

public class Mesh {
  private FloatBuffer vertexBuffer;
  public final int GL20Program;
  private int PositionHandle;
  private int ColorHandle;
  private int MVPMatrixHandle;
  private int colorOverridesTexture = 0;
  private int vertexCount = 1;
  private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex
  private int[] drawOrder; // TODO: Implement
  static final int COORDS_PER_VERTEX = 3;
  private float vertexCoords[];
  float color[] = new float[3];
  private String vertexShaderCode;
  private String fragmentShaderCode;
  private final String defaultVertexShaderCode = "uniform mat4 uMVPMatrix;" + "attribute vec4 vPosition;" + "void main() }" + "  gl_Position = uMVPMatrix * vPosition;" + "}";
  private final String defaultFragmentShaderCode = "precision mediump float;" + "uniform vec4 vColor;" + "void main() }" + "  gl_FragColor = vColor;" + "}";

  public Mesh( int newVertexCount, float[] newVertexCoords, int[] newDrawOrder, int useColor, float[] newColor, String newVertexShaderCode, String newFragmentShaderCode ) {
    vertexCount = newVertexCount;
    vertexCoords = newVertexCoords;
    drawOrder = newDrawOrder;
    colorOverridesTexture = useColor;
    color = newColor;
    vertexShaderCode = newVertexShaderCode;
    fragmentShaderCode = newFragmentShaderCode;
    ByteBuffer bb = ByteBuffer.allocateDirect( vertexCoords.length * 4 );
    bb.order(ByteOrder.nativeOrder());
    vertexBuffer = bb.asFloatBuffer();
    vertexBuffer.put( vertexCoords );
    vertexBuffer.position( 0 );
    int vertexShader = GL20Renderer.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
    int fragmentShader = GL20Renderer.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
    GL20Program = GLES20.glCreateProgram();
    GLES20.glAttachShader(GL20Program, vertexShader);
    GLES20.glAttachShader(GL20Program, fragmentShader);
    GLES20.glLinkProgram(GL20Program);
  }

  public void draw(float[] mvpMatrix) {
    MVPMatrixHandle = GLES20.glGetUniformLocation(GL20Program, "uMVPMatrix");
    GLES20.glUniformMatrix4fv(MVPMatrixHandle, 1, false, mvpMatrix, 0);
    GLES20.glUseProgram(GL20Program);
    PositionHandle = GLES20.glGetAttribLocation(GL20Program, "vPosition");
    GLES20.glEnableVertexAttribArray(PositionHandle);
    GLES20.glVertexAttribPointer(PositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer);
    ColorHandle = GLES20.glGetUniformLocation(GL20Program, "vColor");
    GLES20.glUniform4fv(ColorHandle, 1, color, 0);
    GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
    GLES20.glDisableVertexAttribArray(PositionHandle);
  }
}

抱歉英文不好。

Answer 1

我认为在GL20Activity.onCreate()阶段，EGL上下文不可用或不是最新的。因此在那里添加了网格，Mesh构造函数中的gl *命令将失败。即使将网格对象添加到列表中，也不会初始化相应的OpenGL元素，因此绘制将失败，或者不绘制任何内容。您可以通过在GL20Activity.onCreate()调用Mesh的构造函数中的gl *语句后检查OpenGL错误来验证这一点。

现在，当您在GL20Renderer.onSurfaceCreated()处执行相同操作时，（我认为这是GL20Renderer.onCreated()的意思），EGL上下文可用且有效，因此所有gl *命令都在Mesh＆＃中39; s构造函数将执行，因此网格的OpenGL组件存在，因此它可以正确显示。

由于此方法在渲染开始时调用，以及每次EGL上下文丢失时，这种方法都是一个方便的地方放置代码来创建需要在创建时创建的资源渲染开始，并且需要在EGL上下文时重新创建迷路了。纹理是您可能想要的资源示例在这里创造。

请参阅https://developer.android.com/reference/android/opengl/GLSurfaceView.Renderer.html了解详情。

如果从特定类的某些方法（OpenGL ES 2）添加网格，则网格不会被绘制

1 个答案: