Opengl ES 1.x NDK实例开发之二:颜色的使用

开发框架介绍请参见： Opengl ES NDK实例开发之一:搭建开发框架

【实例讲解】

本章在第一章的基础上讲解颜色的使用。

本例中绘制了一个三角形和一个正方形，三角形用的是光滑着色，正方形用的是平面着色。使用Flat coloring(单调着色)给四边形涂上固定的一种颜色。使用Smooth coloring(平滑着色)将三角形的三个顶点的不同颜色混合在一起，创建漂亮的色彩混合。

[单一颜色渲染]

glColor4f(1.0f, 0.0f, 0.0f, 1.0f);

[顶点渲染混合]

glEnableClientState(GL_COLOR_ARRAY);			// 启用颜色数组
glColorPointer(4, GL_FLOAT, 0, gColors);                // 指定颜色数组
glDisableClientState(GL_COLOR_ARRAY);			// 关闭颜色数组

需注意的是，如果调用了glEnableClientState(GL_COLOR_ARRAY)，则在代码中就要调用glColorPointer(4, GL_FLOAT, 0, gColors)来指定颜色数组，否则在glDrawArrays(GL_TRIANGLES, 0, 3)会因找不到颜色数组而报错

【实例源码】

[GLJNIActivity.java]

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * author: [email protected]
 */

package com.android.gljni;

import com.android.gljni.GLJNIView;

import android.app.Activity;
import android.os.Bundle;

public class GLJNIActivity extends Activity {
	GLJNIView mView;

	@Override
	protected void onCreate(Bundle icicle) {
		super.onCreate(icicle);
		mView = new GLJNIView(getApplication());
		setContentView(mView);
	}

	@Override
	protected void onPause() {
		super.onPause();
		mView.onPause();
	}

	@Override
	protected void onResume() {
		super.onResume();
		mView.onResume();
	}
}

[GLJNIView.java]

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * author: [email protected]
 */

package com.android.gljni;

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

import com.android.gljni.GLJNILib;

import android.content.Context;
import android.opengl.GLSurfaceView;

/**
 * A simple GLSurfaceView sub-class that demonstrate how to perform
 * OpenGL ES 1.x rendering into a GL Surface.
 */
public class GLJNIView extends GLSurfaceView {

	private static final String LOG_TAG = GLJNIView.class.getSimpleName();

	private Renderer renderer;

	public GLJNIView(Context context) {
		super(context);

		// setEGLConfigChooser会对fps产生影响
		setEGLConfigChooser(8, 8, 8, 8, 16, 0);

		renderer = new Renderer(context);
		setRenderer(renderer);
	}

	private static class Renderer implements GLSurfaceView.Renderer {

		public Renderer(Context ctx) {

		}

		public void onDrawFrame(GL10 gl) {
			GLJNILib.step();
		}

		public void onSurfaceChanged(GL10 gl, int width, int height) {
			GLJNILib.resize(width, height);
		}

		public void onSurfaceCreated(GL10 gl, EGLConfig config) {
			GLJNILib.init();
		}
	}

}

[GLJNILib.java]

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * author: [email protected]
 */

package com.android.gljni;

//Wrapper for native library
public class GLJNILib {
	
	static {
		System.loadLibrary("gljni");
	}

	/**
     * @param width the current view width
     * @param height the current view height
     */
	public static native void resize(int width, int height); 
	
    public static native void step();  
    
    public static native void init();  
}

[gl_code.cpp]

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * author: 	[email protected]
 * created:	2014/09/26
 * purpose:	颜色的使用
 */

// OpenGL ES 1.x code

#include <jni.h>
#include <android/log.h>

#include <GLES/gl.h>
#include <GLES/glext.h>

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

/************************************************************************/
/*                             定义                                     */
/************************************************************************/

#define  LOG_TAG    "libgljni"
#define  LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

// 定义π
const GLfloat PI = 3.1415f;

// 顶点数组
const GLfloat gVertices[] = {
	0.0f, 1.0f, 0.0f,	// 上
	-1.0f,-1.0f, 0.0f,	// 左下
	1.0f,-1.0f, 0.0f,	// 右下
};

const GLfloat gVerticesSquare[] = {
	-1.0f, -1.0f, 0.0f, // 左下
	1.0f, -1.0f, 0.0f, 	// 右下
	-1.0f, 1.0f, 0.0f, 	// 左上
	1.0f, 1.0f, 0.0f 	// 右上
};

// 颜色数组
const GLfloat gColors[] = {
	1.0f,0.0f,0.0f, 1.0f,
	0.0f,1.0f,0.0f, 1.0f,
	0.0f,0.0f,1.0f, 1.0f,
};

/************************************************************************/
/*                             C++代码                                  */
/************************************************************************/

static void printGLString(const char *name, GLenum s) {
	const char *v = (const char *) glGetString(s);
	LOGI("GL %s = %s\n", name, v);
}

static void checkGlError(const char* op) {
	for (GLint error = glGetError(); error; error
		= glGetError()) {
			LOGI("after %s() glError (0x%x)\n", op, error);
	}
}

bool init() {
	printGLString("Version", GL_VERSION);
	printGLString("Vendor", GL_VENDOR);
	printGLString("Renderer", GL_RENDERER);
	printGLString("Extensions", GL_EXTENSIONS);

	// 启用阴影平滑
	glShadeModel(GL_SMOOTH);

	// 黑色背景	
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);	

	// 设置深度缓存	
	glClearDepthf(1.0f);

	// 启用深度测试
	glEnable(GL_DEPTH_TEST);	

	// 所作深度测试的类型	
	glDepthFunc(GL_LEQUAL);	

	// 对透视进行修正	
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	

	return true;
}

static void _gluPerspective(GLfloat fovy, GLfloat aspect, GLfloat zNear, GLfloat zFar)
{
	GLfloat top = zNear * ((GLfloat) tan(fovy * PI / 360.0));
	GLfloat bottom = -top;
	GLfloat left = bottom * aspect;
	GLfloat right = top * aspect;
	glFrustumf(left, right, bottom, top, zNear, zFar);
}

void resize(int width, int height)
{
	// 防止被零除
	if (height==0)								
	{
		height=1;
	}

	// 重置当前的视口
	glViewport(0, 0, width, height);	
	// 选择投影矩阵	
	glMatrixMode(GL_PROJECTION);	
	// 重置投影矩阵	
	glLoadIdentity();							

	GLfloat ratio = (GLfloat)width/(GLfloat)height;

	// 设置视口的大小
	_gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	// 选择模型观察矩阵
	glMatrixMode(GL_MODELVIEW);	

	// 重置模型观察矩阵
	glLoadIdentity();							
}

void renderFrame() {
	// 清除屏幕及深度缓存
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  
	// 设置背景颜色为黑色
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
	// 重置当前的模型观察矩阵
	glLoadIdentity();		
	
	// 启用顶点数组
	glEnableClientState(GL_VERTEX_ARRAY);

	// 绘制三角形
	glTranslatef(0.0f,2.0f,-10.0f);						// 设置三角形位置
	glEnableClientState(GL_COLOR_ARRAY);				// 启用颜色数组
	glColorPointer(4, GL_FLOAT, 0, gColors);			// 指定颜色数组
	glVertexPointer(3, GL_FLOAT, 0, gVertices);			// 指定顶点数组
	glDrawArrays(GL_TRIANGLES, 0, 3);					// 绘制三角形
	glDisableClientState(GL_COLOR_ARRAY);				// 关闭颜色数组
	
	// 绘制正方形
	glTranslatef(0.0f,-4.0f,0.0f);						// 设置正方形位置
	glColor4f(1.0f, 0.0f, 0.0f, 1.0f);					// 设置颜色为红色
	glVertexPointer(3, GL_FLOAT, 0, gVerticesSquare);	// 指定顶点数组
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);				// 绘制正方形
	
	// 关闭顶点数组
	glDisableClientState(GL_VERTEX_ARRAY);
}

/************************************************************************/
/*                          JNI代码                                     */
/************************************************************************/

extern "C" {
	JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_resize(JNIEnv * env, jobject obj,  jint width, jint height);
	JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_step(JNIEnv * env, jobject obj);
	JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_init(JNIEnv * env, jobject obj);
};

JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_resize(JNIEnv * env, jobject obj,  jint width, jint height)
{
	resize(width, height);
}

JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_step(JNIEnv * env, jobject obj)
{
	renderFrame();
}

JNIEXPORT void JNICALL Java_com_android_gljni_GLJNILib_init(JNIEnv * env, jobject obj)
{
	init();
}

[Android.mk]

LOCAL_PATH:= $(call my-dir)  
  
include $(CLEAR_VARS)  
  
LOCAL_MODULE    := libgljni  
LOCAL_CFLAGS    := -Werror
LOCAL_SRC_FILES := gl_code.cpp  
LOCAL_LDLIBS    := -llog -lGLESv1_CM  
  
include $(BUILD_SHARED_LIBRARY)