Scratch

Ever seen a 3-d project in which the author called it a "ray caster"? Have you been amazed by that project showing a 3-d interactive environment, yet didn't know how to script it? Here is a guide to making a sprite based raycaster:

What you will need
• 1 sprite based map
• 1 movement sprite
• 1 wall sensing sprite
• 1 (recommended 4) sensors
• 1 (recommended 2) drawers

Step 1: Creating your map
Your map could be anything you want it to be, but I recommend for your first time having a map look sort of like this:

_________________
|                       |
|     _________    |
|    |            |    |
|    |________|    |
|                       |
|_______________|

add this script to it:

when gf clicked
go to x: [0] y: [0]
set [ghost v] effect to [100]

Step 2: Movement
Get your movement sprite and make it a 1 pixel large costume. Then put it inside the outer walls of you map sprite but outside the inner walls. Like this:
_________________
|               •       |
|     _________    |
|    |            |    |
|    |________|    |
|                       |
|_______________|

Where the dot represents the sprite.

Then add this script to it

when gf clicked
go to x: [-20] y: [0] //assuming that that is where you put your sprite
set [drawing v] to [0] 
set [touching wall v] to [0]
set [ghost v] effect to [100]
forever
if <not<(drawing)=[1]>>
if <key [right arrow v] pressed?>
turn cw [2] degrees
broadcast [sense v]
end
if <key [left arrow v] pressed?>
turn cw [-2] degrees
broadcast [sense v]
end
if <not<(touching wall)=[1]>>
if <key [up arrow v] pressed?>
move <speed> steps //where speed is the desired amount of steps you want it to move
broadcast [sense v]
end
end
if <not<(touching wall)=[-1]>>
if <key [down arrow v] pressed?>
move <<speed>*[-1]> steps //where speed is the desired amount of steps you want it to move
broadcast [sense v]
end
end
end

Step 3: Wall sensing
You now have your map and something that moves around in that map, but the only think that would stop it moving is variable values. So, we're going to make those values go to use.
Add this script to your wall sensing sprite.

when gf clicked
set [ghost v] effect to [100]
forever
if <not<(drawing)=[1]>>
go to [movement v] //where movement is the movement sprite
point in direction <[direction v] of [movement v]>
move <speed> steps
if <touching [walls v]?> //the map sprite
set [touching wall v] to [1]
else
set [touching wall v] to [0]
move <<speed>*[-2]> steps
if <touching [walls v]?>
set [touching walls v] to [-1]
else
set [touching wals v] to [0]
end
end
end

Now you can move around your map without going through walls.

Step 4: Distance sensing
This is the sensing script if you only have one sensor. You should divide up the numbers and for each sprite make a new list.

when gf clicked
set [ghost v] effect to [0]
delete (all v) of [distances v]
go to [movement v]

When I receive [sense v] //the broadcast from before
set [drawing v] to [1]
delete (all v) of [distances v]
set [distance v] to [0]
set [angle offset v] to [48]
repeat [96]
set [distance v] to [60]
go to [movement v]
point in direction <<[direction v] of [movement v]> + (angle offset)>
repeat until <<touching [walls v]?> or <(distance) = [0]>>
move (1) steps
change [distance v] by [-1]
end
add (distance) to [distances v]
change [angle offset v] by [-1]
end
wait until <(length of all lists) = [96]> //if you have other sensors
broadcast [draw v]

Step 5: Drawing
Divide up all the lists between all of the drawing sprites you have. Here is a script if you have only 1 drawer and 1 distance sensor

when I receive [draw v] 
go to x: [-237.5] y: [180]
set pen size to [5] //because 96*5=480 which is the width of the screen
set pen color to (color you want)
clear
pen up
set [help counting v] to <length of [distances v]> 
repeat <length of [distances v]>
set pen shade to <<item (help counting) of [distances v]>*<[1]+<[2]/[3]>>> 
set y to <<item (help counting) of [distances v]>*[4]>
pen down
set y to <<<item (help counting) of [distances v]>*[4]>*[-1]>
pen up
change [help counting v] by [-1]
set pen shade to [0]
change x by [5]
end
set [drawing v] to [0]

Next Update: Guide to Array Based Raycasters

Last edited by TorbyFork234 (2012-04-29 15:00:42)