怎么在Android中利用OpenGLES绘制一个天空盒？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。
第一步
SkyBoxView继承了GLSurfaceView，为什么要继承GLSurfaceView，因为在使用OpenGLES需要建立一个窗口和一个上下文，GLSurfaceView帮我们做了这些工作。下面是SkyBoxView的主要代码：
class SkyBoxView(context: Context, attributeSet: AttributeSet?) : GLSurfaceView(context, attributeSet)
{
private lateinit var skyBoxRender: SkyBoxRender
private var lastX=0F
private var lastY=0F
private var yaw=0f
private var pitch=0f
private var screenWidth=0
private var screenHeight=0
private var horSensity=0.03f
private var verSensity=0.03f
constructor(context: Context) : this(context, null)
init
{
// initSensor()
initSensity()
initConfig()
}
private fun initSensity()
{
screenWidth=resources.displayMetrics.widthPixels
screenHeight=resources.displayMetrics.heightPixels
horSensity= 360.0f/screenWidth
verSensity=180.0f/screenHeight
}
private fun rotate(pitch:Float,yaw:Float)
{
queueEvent {
skyBoxRender.rotate(pitch,yaw)
}
}
private fun initConfig()
{
setEGLContextClientVersion(3)
skyBoxRender=SkyBoxRender(context)
setRenderer(skyBoxRender)
renderMode = GLSurfaceView.RENDERMODE_CONTINUOUSLY
}
override fun onTouchEvent(event: MotionEvent?): Boolean
{
when(event?.action)
{
MotionEvent.ACTION_DOWN->
{
lastX=event.x
lastY=event.y
return true
}
MotionEvent.ACTION_MOVE->
{
val offsetX=event.x-lastX
val offsetY=lastY-event.y
yaw+=offsetX*horSensity
pitch+=offsetY*verSensity
lastX=event.x
lastY=event.y
skyBoxRender.rotate(pitch,yaw)
}
}
return true
}
}在initConfig方法里，设置了render为SkyBoxRender，真正的绘制是在这里进行的。在initSensity方法里设置了旋转精度， horSensity和verSensity,水平和数值旋转时的精度，就像你玩fps游戏设置的鼠标灵敏度一样。在onTouchEvent则根据手指滑动的距离设置俯仰角pitch和偏移脚yaw，调用skyBoxRender进行相机的旋转。另外如果你看github可能发现我注释掉了很多代码，那是用传感器旋转的尝试，但是觉得麻烦，也没继续做，有兴趣的读者可以自己搞一下。
第二步
SkyboxRender的主要工作就是加载贴在正方体表面的6个图片纹理,从文件读取着色器语言，而真正创建opengles program和绘制是用C++代码来写的，所以主要看一下这里。
#include#include #include #include #include #include extern "C" { JNIEXPORT jint JNICALL Java_com_skateboard_skybox_SkyBoxRender_genProgram(JNIEnv *env, jobject thiz, jstring vertexPath, jstring fragmentPath) { //load program const char *cVertexPath = env->GetStringUTFChars(vertexPath, nullptr); const char *cFragmentPath = env->GetStringUTFChars(fragmentPath, nullptr); int program = glutils::loadProgram(cVertexPath, cFragmentPath); return program; } JNIEXPORT jint JNICALL Java_com_skateboard_skybox_SkyBoxRender_preparePos(JNIEnv *env, jobject thiz, jfloatArray pos) { //gen vao vbo unsigned int VAO, VBO; glGenVertexArrays(1, &VAO); glBindVertexArray(VAO); glGenBuffers(1, &VBO); glBindBuffer(GL_ARRAY_BUFFER, VBO); int posSize = env->GetArrayLength(pos); float* p=env->GetFloatArrayElements(pos, nullptr); glBufferData(GL_ARRAY_BUFFER, posSize* sizeof(float), p, GL_STATIC_DRAW); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), 0); glBindVertexArray(0); return VAO; } JNIEXPORT jint JNICALL Java_com_skateboard_skybox_SkyBoxRender_prepareTexture(JNIEnv *env, jobject thiz) { //gen texture unsigned int TEXTURE; glGenTextures(1, &TEXTURE); glBindTexture(GL_TEXTURE_CUBE_MAP, TEXTURE); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE); return 1; } glm::vec3 cameraPos = glm::vec3(0.0f, 0.0f, 0.0f); glm::vec3 cameraFront = glm::vec3(0.0f, 0.0f, -1.0f); JNIEXPORT void JNICALL Java_com_skateboard_skybox_SkyBoxRender_draw(JNIEnv *env, jobject thiz, jint program, jint VAO, jint texture,jfloat width,jfloat height) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glClearColor(0.0, 1.0, 0.0, 1.0); glUseProgram(program); glEnable(GL_DEPTH_TEST); glm::mat4 viewMatrix = glm::mat4(1.0f); glm::mat4 projectionMatrix = glm::mat4(1.0f); glm::vec3 v = glm::vec3(cameraFront.x - cameraPos.x, cameraFront.y - cameraPos.y, cameraFront.z - cameraPos.z); viewMatrix = glm::lookAt(cameraPos, v, glm::vec3(0.0f, 1.0f, 0.0f)); projectionMatrix = glm::perspective(glm::radians(45.0f), width / height, 0.1f, 100.0f); int viewMatrixLocation = glGetUniformLocation(program, "view"); int projectMatrixLocation = glGetUniformLocation(program, "projection"); glUniformMatrix4fv(viewMatrixLocation, 1, GL_FALSE, &viewMatrix[0][0]); glUniformMatrix4fv(projectMatrixLocation, 1, GL_FALSE, &projectionMatrix[0][0]); glBindVertexArray(VAO); glBindTexture(GL_TEXTURE_CUBE_MAP, texture); glDrawArrays(GL_TRIANGLES, 0, 36); }
JNIEXPORT void JNICALL
Java_com_skateboard_skybox_SkyBoxRender_rotate(JNIEnv *env, jobject thiz,jfloat pitch,jfloat yaw) {
if(pitch>89)
{
pitch=89.0;
}
if(pitch<-89)
{
pitch=-89.0;
}
cameraFront.x=glm::cos(glm::radians(pitch))*glm::cos(glm::radians(yaw));
cameraFront.y=glm::sin(glm::radians(pitch));
cameraFront.z=glm::cos(glm::radians(pitch))*glm::sin(glm::radians(yaw));
cameraFront=glm::normalize(cameraFront);
}
}genProgram主要是用来产生opengl es的program的，如果对这个概念不太理解请参考C++编译过程。
preparePos是将java层顶点位置数组传入进来并写入顶点着色器。
prepareTexture用来生成纹理。
draw用来进行绘制。
旋转的时候就是通过改变cameraFront的单位向量的方向来做到的。
看完上述内容，你们掌握怎么在Android中利用OpenGLES绘制一个天空盒的方法了吗？如果还想学到更多技能或想了解更多相关内容，欢迎关注创新互联行业资讯频道，感谢各位的阅读！
