Opengl ES 1.x NDK实例开发之二:颜色的使用

转自：http://blog.csdn.net/mnorst/article/details/39580949

【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)