Need Some Explanation on View.Update

[The 10]

Hi, i need help understanding this program, its the smooth animation example from the turing examples.

code:

% The "SmoothAnimateHouse" program. % This program demonstrates the View.Update and setscreen ("offscreenonly") % Draw a house drawbox (30, 30, 100, 100, black) drawbox (50, 30, 80, 60, brightred) drawbox (35, 70, 55, 90, green) drawline (45, 70, 45, 90, green) drawline (35, 80, 55, 80, green) drawbox (75, 70, 95, 90, green) drawline (85, 70, 85, 90, green) drawline (75, 80, 95, 80, green) drawline (30, 100, 65, 135, brightblue) drawline (65, 135, 100, 100, brightblue) drawline (90, 110, 90, 150, black) drawline (75, 125, 75, 150, black) drawline (75, 150, 90, 150, black) locate (maxrow, 2) put "Home sweet home" .. % Create the picture const PIC_WIDTH := 130 const PIC_HEIGHT := 160 var pic := Pic.New (0, 0, PIC_WIDTH, PIC_HEIGHT) % Animate 10 of them around the screen var x, y, dx, dy : array 1 .. 10 of int cls for i : 1 .. 10     x (i) := Rand.Int (10, maxx - 10 - PIC_WIDTH)     y (i) := Rand.Int (10, maxy - 10 - PIC_HEIGHT)     dx (i) := Rand.Int (-3, 3)     dy (i) := Rand.Int (-3, 3) end for loop     cls     locate (maxrow, 10)     put "Old Animation Technique.  Press any key to see the new technique" ..     for i : 1 .. 10         if x (i) + dx (i) < 0 or x (i) + dx (i) + PIC_WIDTH > maxx then             dx (i) := -dx (i)         end if         if y (i) + dy (i) < 0 or y (i) + dy (i) + PIC_HEIGHT > maxy then             dy (i) := -dy (i)         end if         x (i) := x (i) + dx (i)         y (i) := y (i) + dy (i)         Pic.Draw (pic, x (i), y (i), picMerge)     end for     exit when hasch end loop % Read the character from the buffer. var ch : string (1) getch (ch) % Now, any drawing to the screen won't appear until a View.Update is % given.  Note that you can turn this off with setscreen ("offscreenonly") loop     cls     locate (maxrow, 10)     put "New Animation Technique.  Press any key to quit" ..     for i : 1 .. 10         if x (i) + dx (i) < 0 or x (i) + dx (i) + PIC_WIDTH > maxx then             dx (i) := -dx (i)         end if         if y (i) + dy (i) < 0 or y (i) + dy (i) + PIC_HEIGHT > maxy then             dy (i) := -dy (i)         end if         x (i) := x (i) + dx (i)         y (i) := y (i) + dy (i)                 % Note this only draws on the offscreen window.  Nothing appears         % in the visible window.         Pic.Draw (pic, x (i), y (i), picMerge)     end for     % All the houses have been drawn.  Now update the screen.     View.Update     exit when hasch end loop setscreen ("nooffscreenonly")

I dont understand what the array is doing in this program, whats the use of it?
I also dont understand how they made the animation?

Im trying to use this same tecnique in my final project so i would appreciate if someone could just explain this program for me.

[Tony]

the array just holds random locations

otherwise the example is quite well commented

you don't need to consern yourself with details of how animation is made, the important points are that the screen is set to

code:

View.Set("offscreenonly")

and that after you're done drawing your entire frame you update the buffer

code:

View.Update

so your program would look like

code:

View.Set("offscreenonly") loop    Draw    Draw    Draw    View.Update    cls end loop

[The 10]

Tony wrote:

the array just holds random locations

Thx for the reply Tony, but i still dont understand why you need the array there? I know it sounds like silly question, but i really wanna know.

Also i understand this is the way animation should be done.

Quote:

code:

View.Set("offscreenonly") loop    Draw    Draw    Draw    View.Update    cls end loop

but i want to make the animation similar to the house one, so that's why i'd like to understand what happens in this part.

code:

loop     cls     locate (maxrow, 10)     put "New Animation Technique.  Press any key to quit" ..     for i : 1 .. 10         if x (i) + dx (i) < 0 or x (i) + dx (i) + PIC_WIDTH > maxx then             dx (i) := -dx (i)         end if         if y (i) + dy (i) < 0 or y (i) + dy (i) + PIC_HEIGHT > maxy then             dy (i) := -dy (i)         end if         x (i) := x (i) + dx (i)         y (i) := y (i) + dy (i)                 % Note this only draws on the offscreen window.  Nothing appears         % in the visible window.         Pic.Draw (pic, x (i), y (i), picMerge)     end for     % All the houses have been drawn.  Now update the screen.     View.Update     exit when hasch end loop

so if someone could explain this to me?

[Rasta Fella]

Note the only difference between both techniques is that the later one has View.Update stuck into the loop. That's what makes the transition of all the "houses" smooth. As for learning Arrays...

Or for further explanation on "flexible arrays" and more check the Turing Walkthrough.

[The 10]

Ok i understand now that the array is there to hold different values in 1 variable name.

Now i want to understand what's going on in this part of the program - the animation

code:

for i : 1 .. 10         if x (i) + dx (i) < 0 or x (i) + dx (i) + PIC_WIDTH > maxx then             dx (i) := -dx (i)         end if         if y (i) + dy (i) < 0 or y (i) + dy (i) + PIC_HEIGHT > maxy then             dy (i) := -dy (i)         end if         x (i) := x (i) + dx (i)         y (i) := y (i) + dy (i)                 % Note this only draws on the offscreen window.  Nothing appears         % in the visible window.         Pic.Draw (pic, x (i), y (i), picMerge)     end for

I want to understand what's going on, as i dont understand how the houses move the way they do, and how they bounce of the edge.