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 <jni.h>
#include <string>
#include <GLUtils/GLUtils.h>
#include <glm/glm.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <glm/gtc/matrix_transform.hpp>
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。
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