Android OpenGL ES 2.0 (一) 画三角形

看Opengl es的相关知识也有几天了。开始动手跟着例子写代码了。现在就先写个最简单的，画个三角形吧，里面包含了最基本的vertex shader和fragment shader的用法.

Activity里设置opengl es版本为2.0，如果没设，会默认用1.0，然后运行会报API未实现exception.

TestActivity.java

package com.android.jayce.test;

import android.app.Activity;
import android.app.ActivityManager;
import android.content.Context;
import android.content.pm.ConfigurationInfo;
import android.opengl.GLSurfaceView;
import android.opengl.GLSurfaceView.Renderer;
import android.os.Bundle;

public class TestActivity extends Activity
{
private GLSurfaceView mGLSurfaceView;

public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
mGLSurfaceView = new GLSurfaceView(this);
final ActivityManager activityManager = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);
final ConfigurationInfo configInfo = activityManager.getDeviceConfigurationInfo();
if(configInfo.reqGlEsVersion >= 0x20000)
{
mGLSurfaceView.setEGLContextClientVersion(2);
Renderer renderer = new TestRenderer();
mGLSurfaceView.setRenderer(renderer);
}

setContentView(mGLSurfaceView);
}

@Override
protected void onResume()
{
// The activity must call the GL surface view's onResume() on activity onResume().
super.onResume();
mGLSurfaceView.onResume();
}

@Override
protected void onPause()
{
// The activity must call the GL surface view's onPause() on activity onPause().
super.onPause();
mGLSurfaceView.onPause();
}
}

然后是Renderer的实现，参数很少，只有点坐标，颜色

TestRenderer.java

package com.android.jayce.test;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import android.opengl.GLES20;
import android.opengl.Matrix;
import android.opengl.GLSurfaceView;

public class TestRenderer implements GLSurfaceView.Renderer
{

private final FloatBuffer mTriangle1Vertices;
private static final int BYTES_PER_FLOAT = 4;
private float[] mMVPMatrix = new float[16];
private float[] mViewMatrix = new float[16];
private float[] mModelMatrix = new float[16];
private float[] mProjectionMatrix = new float[16];
private int mMVPMatrixHandle;
private int mPositionHandle;
private int mColorHandle;
private final int POSITION_OFFSET = 0;
private final int COLOR_OFFSET = 3;
private final int POSITION_DATA_SIZE = 3;
private final int COLOR_DATA_SIZE = 4;
private final int STRIDE = 7 * BYTES_PER_FLOAT;

public TestRenderer()
{
final float[] triangle1VerticesData = {
// X, Y, Z,
// R, G, B, A
-0.5f, -0.25f, 0.0f,
1.0f, 0.0f, 0.0f, 1.0f,

0.5f, -0.25f, 0.0f,
0.0f, 0.0f, 1.0f, 1.0f,

0.0f, 0.559016994f, 0.0f,
0.0f, 1.0f, 0.0f, 1.0f};

mTriangle1Vertices = ByteBuffer.allocateDirect(triangle1VerticesData.length * BYTES_PER_FLOAT)
.order(ByteOrder.nativeOrder()).asFloatBuffer();
mTriangle1Vertices.put(triangle1VerticesData).position(0);
}

@Override
public void onDrawFrame(GL10 gl) {
// TODO Auto-generated method stub
GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);

Matrix.setIdentityM(mModelMatrix, 0);
drawTriandle(mTriangle1Vertices);
}

private void drawTriandle(final FloatBuffer triangleBuffer)
{
triangleBuffer.position(POSITION_OFFSET);
GLES20.glVertexAttribPointer(mPositionHandle, POSITION_DATA_SIZE, GLES20.GL_FLOAT, false, STRIDE, triangleBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);

triangleBuffer.position(COLOR_OFFSET);
GLES20.glVertexAttribPointer(mColorHandle, COLOR_DATA_SIZE, GLES20.GL_FLOAT, false, STRIDE, triangleBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);

Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);

GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
}

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
// TODO Auto-generated method stub
GLES20.glViewport(0, 0, width, height);

final float ratio = (float) width / height;
final float left = -ratio;
final float right = ratio;
final float bottom = -1.0f;
final float top = 1.0f;
final float near = 1.0f;
final float far = 10.0f;

Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near, far);
}

@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
// TODO Auto-generated method stub
GLES20.glClearColor(0f, 0f, 0f, 1f);

// Position the eye behind the origin.
final float eyeX = 0.0f;
final float eyeY = 0.0f;
final float eyeZ = 1.5f;

// We are looking toward the distance
final float lookX = 0.0f;
final float lookY = 0.0f;
final float lookZ = -5.0f;

// Set our up vector. This is where our head would be pointing were we holding the camera.
final float upX = 0.0f;
final float upY = 1.0f;
final float upZ = 0.0f;

// Set the view matrix. This matrix can be said to represent the camera position.
// NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination of a model and
// view matrix. In OpenGL 2, we can keep track of these matrices separately if we choose.
Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);

final String vertexShader =
"uniform mat4 u_MVPMatrix;      \n"        // A constant representing the combined model/view/projection matrix.

+ "attribute vec4 a_Position;     \n"        // Per-vertex position information we will pass in.
+ "attribute vec4 a_Color;        \n"        // Per-vertex color information we will pass in.

+ "varying vec4 v_Color;          \n"        // This will be passed into the fragment shader.

+ "void main()                    \n"        // The entry point for our vertex shader.
+ "{                              \n"
+ "   v_Color = a_Color;          \n"        // Pass the color through to the fragment shader.
// It will be interpolated across the triangle.
+ "   gl_Position = u_MVPMatrix   \n"     // gl_Position is a special variable used to store the final position.
+ "               * a_Position;   \n"     // Multiply the vertex by the matrix to get the final point in
+ "}                              \n";    // normalized screen coordinates.

final String fragmentShader =
"precision mediump float;       \n"        // Set the default precision to medium. We don't need as high of a
// precision in the fragment shader.
+ "varying vec4 v_Color;          \n"        // This is the color from the vertex shader interpolated across the
// triangle per fragment.
+ "void main()                    \n"        // The entry point for our fragment shader.
+ "{                              \n"
+ "   gl_FragColor = v_Color;     \n"        // Pass the color directly through the pipeline.
+ "}                              \n";

int vertexShaderHandle = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
if(vertexShaderHandle != 0)
{
GLES20.glShaderSource(vertexShaderHandle, vertexShader);
GLES20.glCompileShader(vertexShaderHandle);

final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(vertexShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);

if(compileStatus[0] == 0)
{
GLES20.glDeleteShader(vertexShaderHandle);
vertexShaderHandle = 0;
}
}

if(vertexShaderHandle == 0)
{
throw new RuntimeException("failed to creating vertex shader");
}

int fragmentShaderHandle = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
if(fragmentShaderHandle != 0)
{
GLES20.glShaderSource(fragmentShaderHandle, fragmentShader);
GLES20.glCompileShader(fragmentShaderHandle);

final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(fragmentShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);

if(compileStatus[0] == 0)
{
GLES20.glDeleteShader(fragmentShaderHandle);
fragmentShaderHandle = 0;
}

}

if(fragmentShaderHandle == 0)
{
throw new RuntimeException("failed to create fragment shader");
}

int programHandle = GLES20.glCreateProgram();
if(programHandle != 0)
{
GLES20.glAttachShader(programHandle, vertexShaderHandle);
GLES20.glAttachShader(programHandle, fragmentShaderHandle);

GLES20.glBindAttribLocation(programHandle, 0, "a_Position");
GLES20.glBindAttribLocation(programHandle, 1, "a_Color");

GLES20.glLinkProgram(programHandle);

final int[] linkStatus = new int[1];
GLES20.glGetProgramiv(programHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);

if(linkStatus[0] == 0)
{
GLES20.glDeleteProgram(programHandle);
programHandle = 0;
}
}

if(programHandle == 0)
{
throw new RuntimeException("failed to create program");
}

mMVPMatrixHandle = GLES20.glGetUniformLocation(programHandle, "u_MVPMatrix");
mPositionHandle = GLES20.glGetAttribLocation(programHandle, "a_Position");
mColorHandle = GLES20.glGetAttribLocation(programHandle, "a_Color");

GLES20.glUseProgram(programHandle);
}

}

最后附上效果图：