[gameprogrammer] Re: Calculating Line-Of-Sight
- From: Jake Briggs <jacob_briggs@xxxxxxxxxxxxxxx>
- To: gameprogrammer@xxxxxxxxxxxxx
- Date: Wed, 09 Nov 2005 09:00:53 +1300
Olof Bjarnason wrote:
On 11/7/05, Jake Briggs <jacob_briggs@xxxxxxxxxxxxxxx> wrote:
Olof Bjarnason wrote:
On 11/6/05, Jake Briggs <jacob_briggs@xxxxxxxxxxxxxxx> wrote:
Olof Bjarnason wrote:
I wouldn't recommend testing against *all* planes in your map -- just
the planes of the wall-cubes that are "candidates". How to find the
candidates? One simple idea is "drawing" a straight line from point A
to point B, testing all walls thus "painted".
How do you find out which walls are "painted", and which one are not
without testing all the walls for an intersection? You would end up
doing all the walls once, then re-testing the candidate walls.
Well, in the line-drawing inner-llop, instead of pixels[pitch*y + x] =
color; or whatever draw-pixel-code you have, you do
if(isWall(x,y))
RayCubeCollisionText(theRay, getCubeAt(x,y));
Where does the x,y value come from? Is that where the player is? Or is
that an incrementing point along the line of sight? If its a point along
the line of sight, then that algorithm is pretty much the same as the
original one....
I think we are talking about different things here, and getting our
signals crossed :)
The problem with the original approach was that it could *miss* walls,
even if we decrease the "interval length" (which would of course make
the algorithm slower also) added at each step.
The line-drawing approach I am talking about, fills every wall on the
line, very much like a line-drawing algorithm from point A to point B
in a painting program would (thus the name!).
Yes, but how do you know which walls are on the line?
When you have such an algorithm from drawing lines on Stephen's grid,
it is easily modified to instead of drawing a "pixel" at location
(x,y), doing the test I mentioned earlier. That's where my x and y
comes from.
So the x,y position is the point at which the line intersects the wall?
/Olof
--
Jacob Briggs
Systems Engineer
Core Technology Limited
Level 1, NZX Centre
11 Cable Street
Wellington
Phone +64 4 499-1108
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