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: mnorst@foxmail.com
*/

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: mnorst@foxmail.com
*/

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: mnorst@foxmail.com
*/

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: 	mnorst@foxmail.com
* 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)