在山寨腾讯“爱消除”游戏项目中，我们使用了两种简单的屏幕拾取技术，这在第五天的教程及山寨腾讯“爱消除”游戏之菜单特效里已经有介绍。
很显然，对于一些有复杂不规则图案，或有层次感的场面，上面的技术并不能满足要求。今天我们将介绍另外一种屏幕拾取的方法。
如下图所示，这个是《教你玩魔方》游戏里的一个场景。
显然，由于以下的原因，用前面介绍的两种技术将很难完成准确的屏幕拾取。
1、中间的魔方体是可以随意缩放的；
2、魔方的每一个面都是可以转动的；
3、每个面在转动过程中，位置都是随时变化的；
4、转动结束后，面上每一个方块都会发生变化；
5、每个方块都有6个面，有些面是可见的，有些面是不可见的，触摸到不同的面，产生的动作效果应该是不一样的。
好，下面详细地看一下DisplaySingleCube函数，该函数分别将方块的6个面渲染出来。
1、DisplaySingleCube用于显示一个小方块，一个完整的魔方需要调用27次这个函数，最后一个参数cubeIndex指定了方块的索引（0~26）
2、DisplaySingleCube函数中的渲染操作分为DRAW和SELECT_PLATE两种模式，在屏幕拾取时，要将模式设置为SELECT_PLATE
3、DRAW模式下，使用纹理渲染；SELECT_PLATE模式下，使用色彩渲染，每个面分别渲染出不同的颜色，详细看下面代码的注释；根据选定的颜色，就可以知道触摸到的是哪一个面了。
//显示单个方块
private void DisplaySingleCube(ST_DreamCube dreamcube, float fX, float fY,float fZ,float fRX,float fRY,float fRZ, int cubeIndex)
{
E_WORKMODE eMode = GetGLMode();
E_COLOR cU, cD, cF, cB, cL, cR;
cU = dreamcube.cube_status[cubeIndex].Color.U;
cD = dreamcube.cube_status[cubeIndex].Color.D;
cF = dreamcube.cube_status[cubeIndex].Color.F;
cB = dreamcube.cube_status[cubeIndex].Color.B;
cL = dreamcube.cube_status[cubeIndex].Color.L;
cR = dreamcube.cube_status[cubeIndex].Color.R;
BindVertexAndTexture(cubeBuff, cubetexBuff);
mGl.glLoadIdentity(); //可不要
GLU.gluLookAt(mGl,
-5.0f, 5.0f, 5.0f,
0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f);
mGl.glScalef(mCfg.cubeConfig.fZoomFactor, mCfg.cubeConfig.fZoomFactor, mCfg.cubeConfig.fZoomFactor);
mGl.glTranslatef((float)0.3, (float)0.3-1, (float)-0.3);
mGl.glFrontFace(GL10.GL_CCW);
if (mCube.fYDegree != 0)
{
mGl.glRotatef(mCube.fYDegree, 0.0f, 1.0f, 0.0f);
}
if (fRX != 0 || fRY != 0 || fRZ != 0)
{
mGl.glRotatef(fRotate, fRX, fRY, fRZ);
}
mGl.glTranslatef(fX, fY, fZ);
// FRONT AND BACK
if (eMode == E_WORKMODE.DRAW)
{
mGl.glBindTexture(GL10.GL_TEXTURE_2D, texture[cF.ordinal()]);
}
else if (eMode == E_WORKMODE.SELECT_PLATE)
{
mGl.glColor4f(0, 0, 1, 1); //RGB(0,0,1) 蓝
}
mGl.glNormal3f(0.0f, 0.0f, 1.0f);
mGl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);
if (eMode == E_WORKMODE.DRAW)
{
mGl.glBindTexture(GL10.GL_TEXTURE_2D, texture[cB.ordinal()]);
}
else if (eMode == E_WORKMODE.SELECT_PLATE)
{
mGl.glColor4f(0, 1, 0, 1); //RGB(0,1,0) 绿
}
mGl.glNormal3f(0.0f, 0.0f, -1.0f);
mGl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 4, 4);
// LEFT AND RIGHT
if (eMode == E_WORKMODE.DRAW)
{
mGl.glBindTexture(GL10.GL_TEXTURE_2D, texture[cL.ordinal()]);
}
else if (eMode == E_WORKMODE.SELECT_PLATE)
{
mGl.glColor4f(0, 1, 1, 1); //RGB(0,0,1) 蓝+绿
}
mGl.glNormal3f(-1.0f, 0.0f, 0.0f);
mGl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 8, 4);
if (eMode == E_WORKMODE.DRAW)
{
mGl.glBindTexture(GL10.GL_TEXTURE_2D, texture[cR.ordinal()]);
}
else if (eMode == E_WORKMODE.SELECT_PLATE)
{
mGl.glColor4f(1, 0, 0, 1); //RGB(0,0,1) 红
}
mGl.glNormal3f(1.0f, 0.0f, 0.0f);
mGl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 12, 4);
// TOP AND BOTTOM
if (eMode == E_WORKMODE.DRAW)
{
mGl.glBindTexture(GL10.GL_TEXTURE_2D, texture[cU.ordinal()]);
}
else if (eMode == E_WORKMODE.SELECT_PLATE)
{
mGl.glColor4f(1, 0, 1, 1); //RGB(0,0,1) 红+蓝
}
mGl.glNormal3f(0.0f, 1.0f, 0.0f);
mGl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 16, 4);
if (eMode == E_WORKMODE.DRAW)
{
mGl.glBindTexture(GL10.GL_TEXTURE_2D, texture[cD.ordinal()]);
}
else if (eMode == E_WORKMODE.SELECT_PLATE)
{
mGl.glColor4f(1, 1, 0, 1); //RGB(0,0,1) 红+绿
}
mGl.glNormal3f(0.0f, -1.0f, 0.0f);
mGl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 20, 4);
}
接下来介绍选择物体的函数SelectObj，参数是手指触碰到屏幕的坐标值。
1、在进入SelectObj函数之前，需要将模式设置为PICK，这样DisplaySingleCube函数内部的DRAW及SELECT_PLATE将不起作用；
2、在绘制每一个小方块之前，调用glColor4f给这个方块设置颜色，每个方块都会设置成不同的颜色，详细看代码注释；
3、我们用（0,0,1）~（1,1,1）来表示不同的颜色，最多只能7种颜色，那么如何用7种颜色来识别27个方块呢？我们采用分组的方法来做到这一点的，详细见代码；
//对象选择操作
E_SELECTION SelectObj(int x, int y)
{
E_SELECTION eObj = E_SELECTION.SELE_INVALID;
int iObj = 0;
InitViewPortMain();
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
{
mCube.XChgDreamCube4Display(mCube.DREAM_CUBE_CACULATE);
mGl.glColor4f(0, 0, 1, 1); // RGB(0,0,1) 蓝色
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, -1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 24);
mGl.glColor4f(0, 1, 0, 1); // RGB(0,1,0) 绿色
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 25);
mGl.glColor4f(0, 1, 1, 1); // RGB(0,1,1) 绿色+蓝色
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 26);
mGl.glColor4f(1, 0, 0, 1); // RGB(1,0,0) 红色
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, -1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 15);
mGl.glColor4f(1, 0, 1, 1); // RGB(1,0,1) 红色+蓝色
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 16);
mGl.glColor4f(1, 1, 0, 1); // RGB(1,1,0) 红色+绿色
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 17);
iObj = GetObj(x, y); //分组1
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_BLK24;
break;
case 2:
eObj = E_SELECTION.SELE_BLK25;
break;
case 3:
eObj = E_SELECTION.SELE_BLK26;
break;
case 4:
eObj = E_SELECTION.SELE_BLK15;
break;
case 5:
eObj = E_SELECTION.SELE_BLK16;
break;
case 6:
eObj = E_SELECTION.SELE_BLK17;
break;
// default:
// eObj = -1;
// break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
mGl.glColor4f(0, 0, 1, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, -1.0f, -1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 6);
mGl.glColor4f(0, 1, 0, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 0f, -1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 7);
mGl.glColor4f(0, 1, 1, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, -1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 8);
mGl.glColor4f(1, 0, 0, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 23);
mGl.glColor4f(1, 0, 1, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 14);
mGl.glColor4f(1, 1, 0, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, -1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 5);
iObj = GetObj(x, y); //分组2
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_BLK6;
break;
case 2:
eObj = E_SELECTION.SELE_BLK7;
break;
case 3:
eObj = E_SELECTION.SELE_BLK8;
break;
case 4:
eObj = E_SELECTION.SELE_BLK23;
break;
case 5:
eObj = E_SELECTION.SELE_BLK14;
break;
case 6:
eObj = E_SELECTION.SELE_BLK5;
break;
// default:
// eObj = -1;
// break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
mGl.glColor4f(0, 0, 1, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, -1.0f, -1.0f, 0.0f, 0.0f, 0.0f, 2);
mGl.glColor4f(0, 1, 0, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, 0.0f, -1.0f, 0.0f, 0.0f, 0.0f, 11);
mGl.glColor4f(0, 1, 1, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, -1.0f, 1.0f, -1.0f, 0.0f, 0.0f, 0.0f, 18);
mGl.glColor4f(1, 0, 0, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 0.0f, 1.0f, -1.0f, 0.0f, 0.0f, 0.0f, 19);
mGl.glColor4f(1, 0, 1, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 1.0f, 1.0f, -1.0f, 0.0f, 0.0f, 0.0f, 20);
mGl.glColor4f(1, 1, 0, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, -1.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 21);
mGl.glColor4f(1, 1, 1, 1);
DisplaySingleCube(mCube.DREAM_CUBE_DISPLAY, 0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 22);
iObj = GetObj(x, y); //分组3
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_BLK2;
break;
case 2:
eObj = E_SELECTION.SELE_BLK11;
break;
case 3:
eObj = E_SELECTION.SELE_BLK18;
break;
case 4:
eObj = E_SELECTION.SELE_BLK19;
break;
case 5:
eObj = E_SELECTION.SELE_BLK20;
break;
case 6:
eObj = E_SELECTION.SELE_BLK21;
break;
case 7:
eObj = E_SELECTION.SELE_BLK22;
break;
// default:
// eObj = -1;
// break;
}
return eObj;
}
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
ShowUnseenPlate(mCube.DREAM_CUBE_CACULATE);
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_LEFT;
break;
case 2:
eObj = E_SELECTION.SELE_RIGHT;
break;
case 3:
eObj = E_SELECTION.SELE_DOWN;
break;
// default:
// eObj = E_Selection.SELE_INVALID;
// break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
ShowLButton();
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_MENU;
break;
case 2:
eObj = E_SELECTION.SELE_HELP;
break;
case 3:
eObj = E_SELECTION.SELE_ZOOMOUT;
break;
case 4:
eObj = E_SELECTION.SELE_DISRUPT;
break;
case 5:
eObj = E_SELECTION.SELE_AUTOPLAY;
break;
case 6:
eObj = E_SELECTION.SELE_RESTART;
break;
case 7:
eObj = E_SELECTION.SELE_STUDY;
break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
ShowRButton();
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_ZOOMIN;
break;
case 2:
eObj = E_SELECTION.SELE_SETUP;
break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
ShowProgressStars();
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_STAR;
break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
ShowCubeTip();
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.TIP_0;
break;
case 2:
eObj = E_SELECTION.TIP_1;
break;
case 3:
eObj = E_SELECTION.TIP_2;
break;
case 4:
eObj = E_SELECTION.TIP_3;
break;
case 5:
eObj = E_SELECTION.TIP_4;
break;
case 6:
eObj = E_SELECTION.TIP_5;
break;
case 7:
eObj = E_SELECTION.TIP_6;
break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
ShowTime(miCubeClockSec);
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_TIMER;
break;
}
return eObj;
}
mGl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
ShowStep(mCube.GetStepBar());
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_STEP;
break;
}
return eObj;
}
return eObj;
}
下面介绍获取对象函数GetObj:
1、根据传入的坐标值，获取指定坐标出的色彩信息；
2、将色彩信息转换为RGB格式，然后返回该信息。
//获取对象
private int GetObj(int x, int y)
{
mGl.glFinish();
mGl.glFinish();
Delay(miSelectDelay);
ByteBuffer pixel = ByteBuffer.allocate(4);
byte data[] = new byte[4];
mGl.glReadPixels(x , iScreenHeight - y, 1, 1, GL10.GL_RGBA, GL10.GL_UNSIGNED_BYTE, pixel);
data = pixel.array();
data[0] = (byte) Math.abs(data[0]);
data[1] = (byte) Math.abs(data[1]);
data[2] = (byte) Math.abs(data[2]);
data[0] = (byte) (data[0] << 2);
data[1] = (byte) (data[1] << 1);
int iObj = data[0] + data[1] + data[2];
return iObj;
}
调用GetObj得到RGB格式的颜色信息，根据该信息，我们可以确定手指触摸到的是哪个方块了：
iObj = GetObj(x, y);
if(iObj != 0)
{
switch(iObj)
{
case 1:
eObj = E_SELECTION.SELE_BLK24;
break;
case 2:
eObj = E_SELECTION.SELE_BLK25;
break;
case 3:
eObj = E_SELECTION.SELE_BLK26;
break;
case 4:
eObj = E_SELECTION.SELE_BLK15;
break;
case 5:
eObj = E_SELECTION.SELE_BLK16;
break;
case 6:
eObj = E_SELECTION.SELE_BLK17;
break;
// default:
// eObj = -1;
// break;
}
return eObj;
}
当触摸事件发生时，我们做了以下事情：
1、将模式设置为PICK
2、用不同颜色来渲染魔方体的各个方块，并拾取到手指触摸处的方块对象
3、将模式设置为DRAW模式
4、按正常的纹理渲染模式，将魔方体完整地渲染出来
case TOUCH:
mCubeGL.SetGLMode(E_WORKMODE.PICK);
GetTouchObj();
mCubeGL.SetGLMode(E_WORKMODE.DRAW);
mCubeGL.DisplayCube();
break;
采用这种方法，只有模式为DRAW的图案会最终显示出来，PICK或SELECT_PLATE模式下的图案是不会显示的，因此，你不需要担心PICK模式下会破坏整体的渲染效果。
好了，完整的代码请参考我的另一个开源项目《教你玩魔方》
项目地址在GITHUB,欢迎你FORK.
https://github.com/3125788/CrazyCube3D