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  • 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;
    
    /**
     * 下面这个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
    		 * 第一个參数表示旋转角度。-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种
    		 *      
    		 *     /|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);
    	}
    
    }
    





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  • 原文地址:https://www.cnblogs.com/lcchuguo/p/5244895.html
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