OpenGL——点的绘制(使用OpenGL来绘制可旋转坐标系的螺旋线)

package com.example.opengl1;

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.GLSurfaceView;
import android.opengl.GLU;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.util.AttributeSet;
import android.view.KeyEvent;
import android.view.Menu;

/**
* 以下这个demo实现了画一个红色的三角形
* @author pc
*
*/
public class MainActivity extends Activity {

MyPointRender1 render;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

MyGLSurfaceView view = new MyGLSurfaceView(this);

render = new MyPointRender1();

//renderer: 渲染器..
view.setRenderer(render);

setContentView(view);
}

class MyGLSurfaceView extends GLSurfaceView{
public MyGLSurfaceView(Context context) {
super(context);
}

public MyGLSurfaceView(Context context,AttributeSet attrs) {
super(context, attrs);
}
}

/**
* 用来控制整个坐标系的旋转
*/
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
float step = 5f;

if(keyCode == KeyEvent.KEYCODE_DPAD_UP){
render.xrotate = render.xrotate - step;
}else if(keyCode == KeyEvent.KEYCODE_DPAD_DOWN){
render.xrotate = render.xrotate + step;
}else if(keyCode == KeyEvent.KEYCODE_DPAD_LEFT){
render.yrotate = render.yrotate + step;
}else if(keyCode == KeyEvent.KEYCODE_DPAD_RIGHT){
render.yrotate = render.yrotate - step;
}

return super.onKeyDown(keyCode, event);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}


package com.example.opengl1;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.util.ArrayList;
import java.util.List;

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

import android.opengl.GLSurfaceView.Renderer;
import android.opengl.GLU;

public class MyPointRender1 implements Renderer {

public float xrotate = 0f;
public float yrotate = 0f;

/**
* 3.
*/
@Override
public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
gl.glColor4f(1f, 0f,0f,1f);

gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glLoadIdentity();
GLU.gluLookAt(gl, 0, 0, 5f, 0, 0, 0, 0, 1, 0);

/**
* gl.glRotatef(-90f, 1, 0, 0):
* 设置旋转角度
*
* gl.glRotatef(-90f, 1, 0, 0):中1,0,0.表示绕x轴旋转
* 第一个参数表示旋转角度。-90f表示顺时针旋转90度.90f表示逆时针旋转90度
*
* 旋转以后的坐标是意图是这样的
*
* /|\z /y
* | /
* | /
* /------->x
*
*
*
*/
gl.glRotatef(xrotate, 1, 0, 0);
gl.glRotatef(yrotate, 0, 1, 0);

float r = 0.5f;
List<Float> coordsList = new ArrayList<Float>();
float x = 0f;
float y = 0f;
float z = 1.5f;
float zstep = 0.005f;

for(float alpha = 0f ; alpha < Math.PI*6 ; alpha = (float)(alpha + Math.PI/32)){
x = (float)(r*Math.cos(alpha));
y = (float)(r*Math.sin(alpha));
z = z - zstep;

coordsList.add(x);
coordsList.add(y);
coordsList.add(z);
}

ByteBuffer ibb = ByteBuffer.allocateDirect(coordsList.size() * 4);
ibb.order(ByteOrder.nativeOrder());
FloatBuffer fbb = ibb.asFloatBuffer();
for(float f : coordsList){
fbb.put(f);
}
ibb.position(0);

gl.glVertexPointer(3, GL10.GL_FLOAT, 0, ibb);
gl.glDrawArrays(GL10.GL_POINTS, 0, coordsList.size() / 3);

}

/**
* 2.
*/
@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
float ratio = (float)width/(float)height;

gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
gl.glFrustumf(-1f, 1f, -ratio, ratio, 3f, 7f);
}

/**
* 1.
*/
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glClearColor(0, 0, 0, 1f);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
}

}