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7-1.OpenGL综合案例(大球自转,小球公转)

7-1.OpenGL综合案例(大球自转,小球公转)

作者: Pufus | 来源:发表于2020-10-10 22:03 被阅读0次

案例的实现效果是在一个场景中绘制地板、大球、小球、公转自转和相机的移动,其中结合了OpenGL中大部分知识点,最终的效果如下图


大球自转,小球公转

主要有以下3部分构成:
1.绿色的地板
2.自转的红色大球
3.50个随机分布的蓝色小球以及1个围绕大球公转的动态小球

整体的流程的如下


整体流程.png

比较重要的逻辑都在以下三个函数中

  • SetupRC函数
  • RenderScene函数
  • SpecialKeys函数

整体的效果的实现,可以大致分为4部分

  • 地板
  • 大球(自转)
  • 小球(包含50个静态小球+1个围绕大球公转的动态小球)
  • 移动(特殊键位上下左右触发)

1、地板绘制

  • SetupRC函数:准备地板的顶点数据
  • RenderScene函数:利用平面着色器绘制地板

两个函数此时的流程图大致如下

地板绘制流程
具体代码:
1.1 声明变量
#include "GLTools.h"
#include "GLShaderManager.h"
#include "GLFrustum.h"
#include "GLBatch.h"
#include "GLMatrixStack.h"
#include "GLGeometryTransform.h"
#include "StopWatch.h"
#include <math.h>
#include <stdio.h>
#ifdef __APPLE__
#include <glut/glut.h>
#else
#define FREEGLUT_STATIC
#include <GL/glut.h>
#endif

GLShaderManager shaderManager;// 着色器管理器
GLMatrixStack modelViewMatrix;// 模型视图矩阵
GLMatrixStack projectionMatrix;// 投影矩阵
GLFrustum viewFrustum;// 视景体
GLGeometryTransform transformPipeline;// 几何图形变换管道

GLTriangleBatch torusBatch;//大球
GLTriangleBatch sphereBatch;//小球
GLBatch floorBatch;//地板

GLFrame cameraFrame;//角色帧 照相机角色帧

#define NUM_SPHERE 50  //小球数量
GLFrame spheres[NUM_SPHERE];

1.2 main函数

int main(int argc, char* argv[])
{
    gltSetWorkingDirectory(argv[0]);
    
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(800,600);
    
    glutCreateWindow("OpenGL SphereWorld");
    
    glutReshapeFunc(ChangeSize);
    glutDisplayFunc(RenderScene);
    
    GLenum err = glewInit();
    if (GLEW_OK != err) {
        fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
        return 1;
    }
    
    
    SetupRC();
    glutMainLoop();    
    return 0;
}

1.3设置视口

//屏幕更改大小或已初始化
void ChangeSize(int nWidth, int nHeight)
{
    //1.设置视口
    glViewport(0, 0, nWidth, nHeight);
    
    //2.创建投影矩阵,。
    viewFrustum.SetPerspective(35.0f, float(nWidth)/float(nHeight), 1.0f, 100.0f);
    //viewFrustum.GetProjectionMatrix()  获取viewFrustum投影矩阵
    //并将其加载到投影矩阵堆栈上
    projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
    
    //3.设置变换管道以使用两个矩阵堆栈(变换矩阵modelViewMatrix ,投影矩阵projectionMatrix)
    //初始化GLGeometryTransform 的实例transformPipeline.通过将它的内部指针设置为模型视图矩阵堆栈 和 投影矩阵堆栈实例,来完成初始化
    //当然这个操作也可以在SetupRC 函数中完成,但是在窗口大小改变时或者窗口创建时设置它们并没有坏处。而且这样可以一次性完成矩阵和管线的设置。
    transformPipeline.SetMatrixStacks(modelViewMatrix, projectionMatrix);
}

1.4 设置地板数据

   void SetupRC()
{
    //1.初始化
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    shaderManager.InitializeStockShaders();
    
    //2.开启深度测试
    glEnable(GL_DEPTH_TEST);
   
    //3. 设置地板顶点数据
    floorBatch.Begin(GL_LINES, 324);
    for(GLfloat x = -20.0; x <= 20.0f; x+= 0.5) {
        floorBatch.Vertex3f(x, -0.55f, 20.0f);
        floorBatch.Vertex3f(x, -0.55f, -20.0f);
        
        floorBatch.Vertex3f(20.0f, -0.55f, x);
        floorBatch.Vertex3f(-20.0f, -0.55f, x);
    }
    floorBatch.End();
}

1.5 地板渲染

    //进行调用以绘制场景
void RenderScene(void)
{
    //1.颜色值(地板,大球,小球颜色)
    static GLfloat vFloorColor[] = { 0.0f, 1.0f, 0.0f, 1.0f};
    static GLfloat vTorusColor[] = { 1.0f, 0.0f, 0.0f, 1.0f };
    //2.清除颜色缓存区和深度缓冲区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    //3.绘制地面
    shaderManager.UseStockShader(GLT_SHADER_FLAT,
                                 transformPipeline.GetModelViewProjectionMatrix(),
                                 vFloorColor);
    //渲染地板
    floorBatch.Draw();
    
    //4.执行缓存区交换
    glutSwapBuffers();
}

运行代码,地板就绘制好了


地板绘制.png

2、大球绘制

  • SetupRC函数:系统模型创建大球
  • RenderScene函数:分为三个部分
    (1). 设置定时器,根据时间变化,设置大球自转
    (2). 设置点光源位置
    (3). 设置大球平移
    (4). 开启定时器,渲染大球

两个函数的流程图如下,图中红框部分流程均与大球相关

大球绘制流程图

具体代码:
2.1 设置大球数据

gltMakeSphere(torusBatch, 0.4f, 40, 80);

void SetupRC()
{
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    shaderManager.InitializeStockShaders();
    
    glEnable(GL_DEPTH_TEST);
    
    floorBatch.Begin(GL_LINES, 324);
    
    for (GLfloat x = -20.0f; x <= 20.0f; x += 0.5) {
        floorBatch.Vertex3f(x, -0.55f, 20.0f);
        floorBatch.Vertex3f(x, -0.55f, -20.0f);
        floorBatch.Vertex3f(20.0f, -0.55f, x);
        floorBatch.Vertex3f(-20.0f, -0.55f, x);
    }
    floorBatch.End();
    
    gltMakeSphere(torusBatch, 0.4f, 40, 80);
}

2.2 大球渲染

//2.基于时间动画
static CStopWatch rotTimer;
float yRot = rotTimer.GetElapsedSeconds() * 60.0f;
//4.获取光源位置
M3DVector4f vLightPos = {0.0f,10.0f,5.0f,1.0f};
//5.使得大球位置平移(3.0)向屏幕里面
modelViewMatrix.Translate(0.0f, 0.0f, -3.0f);
//6.压栈(复制栈顶)
modelViewMatrix.PushMatrix();
//7.大球自转
modelViewMatrix.Rotate(yRot, 0.0f, 1.0f, 0.0f);
//8.指定合适的着色器(点光源着色器)
shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transformPipeline.GetModelViewMatrix(),
transformPipeline.GetProjectionMatrix(), vLightPos, vTorusColor);
torusBatch.Draw();
//9.绘制完毕则Pop
modelViewMatrix.PopMatrix();

   //进行调用以绘制场景
void RenderScene(void)
{
    //1.颜色值(地板,大球,小球颜色)
    static GLfloat vFloorColor[] = { 0.0f, 1.0f, 0.0f, 1.0f};
    static GLfloat vTorusColor[] = { 1.0f, 0.0f, 0.0f, 1.0f };
    
    //2.基于时间动画
    static CStopWatch    rotTimer;
    float yRot = rotTimer.GetElapsedSeconds() * 60.0f;
    
    //2.清除颜色缓存区和深度缓冲区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    //**// 压栈
    modelViewMatrix.PushMatrix();
    
    //3.绘制地面
    shaderManager.UseStockShader(GLT_SHADER_FLAT,
                                 transformPipeline.GetModelViewProjectionMatrix(),
                                 vFloorColor);
    floorBatch.Draw();
    
    
    //4.获取光源位置
    M3DVector4f vLightPos = {0.0f,10.0f,5.0f,1.0f};
   
    //5.使得大球位置平移(3.0)向屏幕里面
    modelViewMatrix.Translate(0.0f, 0.0f, -3.0f);
    //6.压栈(复制栈顶)
    modelViewMatrix.PushMatrix();
    //7.大球自转
    modelViewMatrix.Rotate(yRot, 0.0f, 1.0f, 0.0f);
    //8.指定合适的着色器(点光源着色器)
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transformPipeline.GetModelViewMatrix(),
                                 transformPipeline.GetProjectionMatrix(), vLightPos, vTorusColor);
    torusBatch.Draw();
    //9.绘制完毕则Pop
    modelViewMatrix.PopMatrix();
    modelViewMatrix.PopMatrix();
    
    //10.执行缓存区交换
    glutSwapBuffers();
    glutPostRedisplay();
}
运行代码,得到地板与大球 地板与大球.png

大球变换的代码如下

//5.使得大球位置平移(3.0)向屏幕里面
modelViewMatrix.Translate(0.0f, 0.0f, -3.0f);
//6.压栈(复制栈顶)
modelViewMatrix.PushMatrix();
//7.大球自转
modelViewMatrix.Rotate(yRot, 0.0f, 1.0f, 0.0f);

Translate:目的是为了更好的观察的大球,因为大球创建时默认是在(0,0,0)原点位置,当前的观察者也处于原点位置,不便于观察
PushMatrix:拷贝矩阵堆栈栈顶并压栈,此时只需要将大球平移一次,然后在平移后坐标基础上围绕y轴旋转,实现自转
Rotate:大球围绕y轴旋转,实现自转

3、小球绘制

  • SetupRC函数:初始化小球数据
  • RenderScene函数:首先绘制50个静态小球,每绘制一个小球都需要进行push和pop操作

3.1 设置小球数据

//5. 设置小球球模型
gltMakeSphere(sphereBatch, 0.1f, 13, 26);
//6. 随机位置放置小球球
for (int i = 0; i < NUM_SPHERES; i++) {
//y轴不变,X,Z产生随机值 这样就可以在同一高度显示
GLfloat x = ((GLfloat)((rand() % 400) - 200 ) * 0.1f);
GLfloat z = ((GLfloat)((rand() % 400) - 200 ) * 0.1f);
//在y方向,将球体设置为0.0的位置,这使得它们看起来是飘浮在眼睛的高度
//对spheres数组中的每一个顶点,设置顶点数据
spheres[i].SetOrigin(x, 0.0f, z);
}

void SetupRC()
{
    //1.初始化
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    shaderManager.InitializeStockShaders();
    
    //2.开启深度测试
    glEnable(GL_DEPTH_TEST);
   
    
    //3. 设置地板顶点数据
    floorBatch.Begin(GL_LINES, 324);
    for(GLfloat x = -20.0; x <= 20.0f; x+= 0.5) {
        floorBatch.Vertex3f(x, -0.55f, 20.0f);
        floorBatch.Vertex3f(x, -0.55f, -20.0f);
        
        floorBatch.Vertex3f(20.0f, -0.55f, x);
        floorBatch.Vertex3f(-20.0f, -0.55f, x);
    }
    floorBatch.End();
    
    //4.设置大球模型
     gltMakeSphere(torusBatch, 0.4f, 40, 80);

    //5. 设置小球球模型
    gltMakeSphere(sphereBatch, 0.1f, 13, 26);
    //6. 随机位置放置小球球
    for (int i = 0; i < NUM_SPHERES; i++) {
        //y轴不变,X,Z产生随机值  这样就可以在同一高度显示
        GLfloat x = ((GLfloat)((rand() % 400) - 200 ) * 0.1f);
        GLfloat z = ((GLfloat)((rand() % 400) - 200 ) * 0.1f);
        //在y方向,将球体设置为0.0的位置,这使得它们看起来是飘浮在眼睛的高度
        //对spheres数组中的每一个顶点,设置顶点数据
        spheres[i].SetOrigin(x, 0.0f, z);
    }
}

3.2 小球渲染

//11.画小球
for (int i = 0; i < NUM_SPHERES; i++) {
modelViewMatrix.PushMatrix();
modelViewMatrix.MultMatrix(spheres[I]);
shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transformPipeline.GetModelViewMatrix(),
transformPipeline.GetProjectionMatrix(), vLightPos, vSphereColor);
sphereBatch.Draw();
modelViewMatrix.PopMatrix();
}

//进行调用以绘制场景
void RenderScene(void)
{
    //1.颜色值(地板,大球,小球颜色)
    static GLfloat vFloorColor[] = { 0.0f, 1.0f, 0.0f, 1.0f};
    static GLfloat vTorusColor[] = { 1.0f, 0.0f, 0.0f, 1.0f};
    static GLfloat vSphereColor[] = { 0.0f, 0.0f, 1.0f, 1.0f};
    
    //2.基于时间动画
    static CStopWatch    rotTimer;
    float yRot = rotTimer.GetElapsedSeconds() * 60.0f;
    
    //3.清除颜色缓存区和深度缓冲区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    modelViewMatrix.PushMatrix();
    
    //4.绘制地面
    shaderManager.UseStockShader(GLT_SHADER_FLAT,
                                 transformPipeline.GetModelViewProjectionMatrix(),
                                 vFloorColor);
    floorBatch.Draw();
    
    
    //5.获取光源位置
    M3DVector4f vLightPos = {0.0f,10.0f,5.0f,1.0f};
    //6.使得大球位置平移(3.0)向屏幕里面
    modelViewMatrix.Translate(0.0f, 0.0f, -3.0f);
    //7.压栈(复制栈顶)
    modelViewMatrix.PushMatrix();
    //8.大球自转
    modelViewMatrix.Rotate(yRot, 0.0f, 1.0f, 0.0f);
    //9.指定合适的着色器(点光源着色器)
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transformPipeline.GetModelViewMatrix(),
                                 transformPipeline.GetProjectionMatrix(), vLightPos, vTorusColor);
    torusBatch.Draw();
    //10.绘制完毕则Pop
    modelViewMatrix.PopMatrix();
    
 
    //11.画小球
    for (int i = 0; i < NUM_SPHERES; i++) {
        //每绘制一个小球都需要进行push和pop操作
        modelViewMatrix.PushMatrix();
        modelViewMatrix.MultMatrix(spheres[I]);
        shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transformPipeline.GetModelViewMatrix(),
                                     transformPipeline.GetProjectionMatrix(), vLightPos, vSphereColor);
        sphereBatch.Draw();
        modelViewMatrix.PopMatrix();
        
    }
    
    modelViewMatrix.PopMatrix();
    //12.执行缓存区交换
    glutSwapBuffers();
    glutPostRedisplay();
}

运行代码,得到地板+大球+小球


地板+大球+小球.png

4、小蓝球围着红球自转

//13. 让一个小蓝球围绕大球自转
modelViewMatrix.Rotate(yRot * -2.0f, 0.0f, 1.0f, 0.0f);
modelViewMatrix.Translate(0.8f, 0.0f, 0.0f);
shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF,transformPipeline.GetModelViewMatrix(),transformPipeline.GetProjectionMatrix(),vLightPos,vSphereColor);
sphereBatch.Draw();

//进行调用以绘制场景
void RenderScene(void)
{
    //1.颜色值(地板,大球,小球颜色)
    static GLfloat vFloorColor[] = { 0.0f, 1.0f, 0.0f, 1.0f};
    static GLfloat vTorusColor[] = { 1.0f, 0.0f, 0.0f, 1.0f};
    static GLfloat vSphereColor[] = { 0.0f, 0.0f, 1.0f, 1.0f};
    
    //2.基于时间动画
    static CStopWatch    rotTimer;
    float yRot = rotTimer.GetElapsedSeconds() * 60.0f;
    
    //3.清除颜色缓存区和深度缓冲区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    modelViewMatrix.PushMatrix();
    
    //5.绘制地面
    shaderManager.UseStockShader(GLT_SHADER_FLAT,
                                 transformPipeline.GetModelViewProjectionMatrix(),
                                 vFloorColor);
    floorBatch.Draw();
    
    
    //6.获取光源位置
    M3DVector4f vLightPos = {0.0f,10.0f,5.0f,1.0f};
   
    //7.使得大球位置平移(3.0)向屏幕里面
    modelViewMatrix.Translate(0.0f, 0.0f, -3.0f);
    //8.压栈(复制栈顶)
    modelViewMatrix.PushMatrix();
    //9.大球自转
    modelViewMatrix.Rotate(yRot, 0.0f, 1.0f, 0.0f);
    //10.指定合适的着色器(点光源着色器)
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transformPipeline.GetModelViewMatrix(),
                                 transformPipeline.GetProjectionMatrix(), vLightPos, vTorusColor);
    torusBatch.Draw();
    //11.绘制完毕则Pop
    modelViewMatrix.PopMatrix();
    
    //12.画小球
    for (int i = 0; i < NUM_SPHERES; i++) {
        modelViewMatrix.PushMatrix();
        modelViewMatrix.MultMatrix(spheres[I]);
        shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transformPipeline.GetModelViewMatrix(),
                                     transformPipeline.GetProjectionMatrix(), vLightPos, vSphereColor);
        sphereBatch.Draw();
        modelViewMatrix.PopMatrix();
    }
    
    //13. 让一个小蓝球围绕大球自转
    modelViewMatrix.Rotate(yRot * -2.0f, 0.0f, 1.0f, 0.0f);
    modelViewMatrix.Translate(0.8f, 0.0f, 0.0f);
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF,transformPipeline.GetModelViewMatrix(),transformPipeline.GetProjectionMatrix(),vLightPos,vSphereColor);
    sphereBatch.Draw();
    
    modelViewMatrix.PopMatrix();
    //14.执行缓存区交换
    glutSwapBuffers();
    glutPostRedisplay();
  }

运行代码,得到一个小蓝球围绕大红球自转


小蓝球围绕大红球自转.gif 小球渲染流程图.png

5、设置视图变换

项目中setupRc、RenderScene、SpecialKeys总的流程图如下


总渲染流程图.png

具体代码如下
5.1加入观察者

//4、加入观察者
M3DMatrix44f mCamera;
cameraFrame.GetCameraMatrix(mCamera);
modelViewMatrix.PushMatrix(mCamera);
modelViewMatrix.PopMatrix();

//进行调用以绘制场景
void RenderScene(void)
{
    //3.
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    //1. 颜色(地板,大球颜色,小球颜色)
    static GLfloat vFloorColor[] = {0.0f,1.0f,0.0f,1.0f};
    static GLfloat vTorusColor[] = {1.0f,0.0f,0.0f,1.0f};
    static GLfloat vSpereColor[] = {0.0f,0.0f,1.0f,1.0f};
    
    //2. 动画
    static CStopWatch rotTimer;
    float yRot = rotTimer.GetElapsedSeconds()*60.0f;
    
    modelViewMatrix.PushMatrix();
    
    M3DMatrix44f mCamera;
    cameraFrame.GetCameraMatrix(mCamera);
    modelViewMatrix.PushMatrix(mCamera);
    
    
    //4.地面绘制;
    shaderManager.UseStockShader(GLT_SHADER_FLAT,transformPipeline.GetModelViewProjectionMatrix(),vFloorColor);
    floorBatch.Draw();
    
    //5. 设置点光源位置
    M3DVector4f vLightPos = {0,10,5,1};
    
    //6. 使得整个大球往里平移3.0
    modelViewMatrix.Translate(0.0f, 0.0f, -3.0f);
    
    //7. 大球
    modelViewMatrix.PushMatrix();
    modelViewMatrix.Rotate(yRot, 0, 1, 0);
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF,transformPipeline.GetModelViewMatrix(),transformPipeline.GetProjectionMatrix(),vLightPos,vTorusColor);
    torusBatch.Draw();
    modelViewMatrix.PopMatrix();
    
    //8. 小球
    for (int i = 0; i < NUM_SPHERES; i++) {
        modelViewMatrix.PushMatrix();
        modelViewMatrix.MultMatrix(spheres[I]);
        shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF,transformPipeline.GetModelViewMatrix(),transformPipeline.GetProjectionMatrix(),vLightPos,vSpereColor);
        sphereBatch.Draw();
        modelViewMatrix.PopMatrix();
        
    }
    
    
    //9.让一个小球围着大球公转;
    modelViewMatrix.Rotate(yRot * -2.0f, 0, 1, 0);
    modelViewMatrix.Translate(0.8f, 0.0f, 0.0f);
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF,transformPipeline.GetModelViewMatrix(),transformPipeline.GetProjectionMatrix(),vLightPos,vSpereColor);
    sphereBatch.Draw();
   
    modelViewMatrix.PopMatrix();
    modelViewMatrix.PopMatrix();
    glutSwapBuffers();
    glutPostRedisplay();
}

5.2 main函数添加SpeacialKeys监听

glutSpecialFunc(SpeacialKeys);

int main(int argc, char* argv[])
{
    gltSetWorkingDirectory(argv[0]);
    
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(800,600);
    
    glutCreateWindow("OpenGL SphereWorld");
    
    glutReshapeFunc(ChangeSize);
    glutDisplayFunc(RenderScene);
    glutSpecialFunc(SpeacialKeys);
    
    GLenum err = glewInit();
    if (GLEW_OK != err) {
        fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
        return 1;
    }
    
    
    SetupRC();
    glutMainLoop();    
    return 0;
}

5.3实现SpeacialKeys键位函数

void SpeacialKeys(int key,int x,int y){
    
    float linear = 0.1f;
    float angular = float(m3dDegToRad(5.0f));
    
    if (key == GLUT_KEY_UP) {
        cameraFrame.MoveForward(linear);
    }
    if (key == GLUT_KEY_DOWN) {
        cameraFrame.MoveForward(-linear);
    }
    
    if (key == GLUT_KEY_LEFT) {
        cameraFrame.RotateWorld(angular, 0, 1, 0);
    }
    if (key == GLUT_KEY_RIGHT) {
        cameraFrame.RotateWorld(-angular, 0, 1, 0);
    }
}

运行代码,就可以对视图进行前进后退旋转操作了


对视图进行前进后退旋转操作.gif

错误分析

运行代码的时候,有可能会出现以下情况,或者运行崩溃

错误.png
\color{rgb(255, 127, 80)}{原因是堆栈的入栈出栈操作没有对应好,入栈与出栈必须一一对应}
入栈出栈操作对应分析.png
如上图,入栈出栈操作一一对应,红色入栈push对应红色出栈pop

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