I downloaded some Processing demo codes,
but they can't run cause <BGraphics not found> and <BImage not found>.

Any clue why ?

for example, I have this problem with blobs.pde
from
http://www.hardcorepawn.com/blobs/

Thanks, I will try that...

I made all the changes I could find,
like BGraphics -> PGraphics,
but blobs.pde still doesn't work.

Since this is a downloaded demo, (not my program), it's difficult to see what's wrong.

Here is the code, in case someone wants to try it:

//blobs
//2007-aug-17
//from http://www.hardcorepawn.com/blobs/

int NUM_BLOBS=100;
boolean keyp=false;

class Blob
{
 float x,y,vx,vy;
 color c;
 int r;
 PGraphics target;
//  Blob(int _x, int _y, PGraphics _target)
 Blob(int _x, int _y, int _r, PGraphics target)
 {
   x=_x;
   y=_y;
   r=_r;
   vx=random(-2,2);
   vy=random(-2,2);
//    target=_target;
   c=color(int(random(255)),int(random(255)),int(random(255)),32);
   
 }
 
 void show() {
  float closest=width*height;
   int k;
   boolean found=false;
   for(int i=int(y-r);i<int(y+r);i++)
   {
     k=i*width;
     if(i>=0&&i<height)
     {
       for(int j=int(x-r);j<int(x+r);j++)
       {
         if(j>=0&&j<width)
         {
           if((overlay.pixels[j+i*width]&0x000000FF)==0)
           {
             found=true;
             int xd=i-int(y);
             int yd=j-int(x);
             if(sqrt(xd*xd+yd*yd)<closest)
             {
               closest=sqrt(xd*xd+yd*yd);
             }
           }
         }
       }
     }
   }
   if(!found)
   {
     closest=width*height;
   }
   if(closest<r)
   {
     int diam=r-int(closest);
     int alpha=254-int((255.0/float(r))*closest);
     fill(red(c),green(c),blue(c),alpha);
     noStroke();
//      ellipse(x-(diam/2),y-(diam/2),x+(diam/2),y+(diam/2));
     ellipse(x-(diam/2),y-(diam/2),diam,diam);
   }
   else
   {
     noStroke();
     fill(red(c),green(c),blue(c),128);
     ellipse(x-1,y-1,2,2);
//      ellipse(x-1,y-1,2,2);
   }
 }//show()
 
 void move() {
   if(x+vx<=0 || x+vy>width)
   {
     vx=-vx;
   }
   if(y+vy<=0 || y+vy>height)
   {
     vy=-vy;
   }
   x+=vx;
   y+=vy;
 }//move()
 
}//class Blob

class Curvepoint
{
 float x,y,vx,vy;
 Curvepoint(float _x, float _y)
 {
   x=_x;
   y=_y;
   vx=random(-5,5);
   vy=random(-5,5);
 }
 
 void move()
 {
   if(x+vy>=width || x+vy<0)
   {
     vx=0-vx;
     vx+=random(-0.5,0.5);
   }
   if(y+vy>=height || y+vy<0)
   {
     vy=0-vy;
     vy+=random(-0.5,0.5);
   }
   x+=vx;
   y+=vy;
 }//move()
 
}//class Curvepoint

Blob[] blobs;
Curvepoint[] points;
PGraphics overlay;

void setup()
{
 size(400,400);
 overlay=createGraphics(width,height,P2D);
 overlay.stroke(0);
 overlay.background(0);
 
 noStroke();
 background(255,255,255);
 
 blobs=new Blob[NUM_BLOBS];
 points=new Curvepoint[8];
 int a=int(sqrt(blobs.length));
 for(int i=0;i<blobs.length;i++)
 {  
   blobs[i]=new Blob(((width/a)/2)+i%a*(width/a),((height/a)/2)+(i/a)*(height/a),width/a,overlay
);
 }
 for(int i=0;i<points.length;i++)
 {
   points[i]=new Curvepoint(random(width),random(height));
 }
}//setup()

void draw()
{
 background(255,255,255);
 overlay.background(255,255,255);
 stroke(0);
 overlay.beginShape();//@@**something WRONG here ??
 {
   for(int i=0;i<points.length;i++)
   {
     overlay.curveVertex(points[i].x,points[i].y);
     points[i].move();
   }
 }
 overlay.endShape();
 for(int i=0;i<blobs.length;i++)
 {
   blobs[i].show();
//    blobs[i].move();
 }
 if(keyp)
 {
   setup();
   keyp=false;
 }
}//draw()

void keyPressed()
{
 if(key=='a' && NUM_BLOBS<12800)
 {
   NUM_BLOBS*=2;
   keyp=true;
 }
 if(key=='z' && NUM_BLOBS>25)
 {
   NUM_BLOBS/=2;
   keyp=true;
 }
}

Ah, that old code.

I've already made a more up to date version: http://www.hardcorepawn.com/blobs2/ does the same sort of thing, but should work with minimal changes in the latest version of processing.

Ah yes, there is one change since then that's affecting it:

overlay.beginShape(LINE_STRIP); needs to be overlay.beginShape(); and then overlay.endShape(); soon after needs to become overlay.endShape(CLOSE);

Ah yes, PGraphics3 is now PGraphics3D I believe. As for house.png, well, you'll have to make your own.