Kitty-corners

Post by **Phineus** » Sun Apr 20, 2003 5:58 am

This is something I've wondered about for a while now but haven't come up with an answer. No, I don't mean clawfford's web site. Have a look at the picture. Can you see what's wrong?

<center><img src="http://mtm2.com/~forum/pics/kittycornertraxx.gif" width="594"></center>

Can't see it? Take a look at the bottom left of that hill, now look at the bottom right. On the left, the base where the hill meets the road is a square wall type shape. On the right, the terrain flattens to form a 45 degree angle at the base - the tile is split into two triangles: one flat on the ground, the other going up the side of the hill. But on the left, it's almost like a ground box with the side toward us and the side toward the road on the very left, going up almost perpendicular to the road surface. The altitudes are a perfect mirror left and right. In other tracks, we see a third result where a ridge goes from the outer most corner back up along to the inner most corner - which looks bad and drives worse.

So, the question is, has anybody figured out a way to predict when the terrain will behave in one of these three ways? In my example picture, I mirror'd left and right in psp, so I have no idea what's causing the difference.

edit. Unless texture rotation has something to do with it.

Malibu350 · Post by **Malibu350** » Sun Apr 20, 2003 11:24 am

I've often wondered that myself but never bothered to look into it.

it seems to be related to the geometry of the entire grid... like it's broken down into odd and even sectors....

in the image below I laid some 4x4 tiles then spiked the center up to 255... the diamond shapes show the folded corners and the squares represent the steep rise at the corner.. http://www.mtmc4fun.com/images/mtmg/Kitty.jpg

that test you did above is 17 squares wide, wonder what happens if you went 18?...

I bet this could be mapped out, since I can already see a pattern begining.

[edit] Kitty2 Kitty3

Edited by Malibu350 (20-04-2003)

Post by **Phineus** » Sun Apr 20, 2003 11:54 am

18 squares and I lose the flattened edge. But that's if I add it to the right. If I add it to the left, that corner gains the flattened spot without losing it on the right. I suspect if I moved the whole (17 square) hill one square either way I'd get a flip flopping of which side has the flattened part and which the wall part. (I'll go try, hold on a sec). Yep, shifting the hill reverses which side is doing what.

The funny thing is that no matter what it looks like in traxx, it looks the same in the game. So, whatever is at work here, it wouldn't seem to be game dependent - I can't see GB knowingly working this quirk into traxx.

ps. rotating has no effect.

Edited by Phineus (20-04-2003)

Wint · Post by **Wint** » Fri Apr 25, 2003 7:10 pm

Interesting stuff.

> has anybody figured out a way to predict when the terrain....

Yeah, just now, toying with terrain in Traxx, it's an even/odd issue, as Mal stated.

> "the diamond shapes show the folded corners and the squares represent the steep rise at the corner"

Very good. Click any one point and it will break one way or the other, in all directions.
One point will create a folded corner/diagonal pyramid.
One point will create a perfect/square pyramid.
Continue diagonally across the grid and the effect will remain consistant.

<center><img src=http://rhinoseros.com/~trackville/pics/matrix3.gif>
eye friendly version?</center>

<center><img src=http://rhinoseros.com/~trackville/pics/matrix.gif>
the alternating grid of square/diagonal geometry</center>

While checking out TrackEd2 I seem to remember seeing that you can have the diagonal grid lines displayed, I dunno if it helped.

Edited by Winterkill (26-04-2003)

Wint · Post by **Wint** » Sat Apr 26, 2003 12:02 am

While the matrix above represents the crosshatched reality, the image below represents an overlay of the two types of peaks. With the red dot in the center representing the raised grid point you see the outlines of a square pyramid in blue and a diagonal pyramid in yellow (with flat-folded corners).

<center><img src=http://rhinoseros.com/~trackville/pics/matrix2.gif>
original</center>

<center><img src=http://rhinoseros.com/~trackville/pics/matrix4.gif>
eye friendly version?</center>

Edited by Winterkill (26-04-2003)

Post by **Phineus** » Sat Apr 26, 2003 1:16 am

I posted a response shortly after yours this morning. Then thought better of it and deleted it again. But now after you hurt my eyes with those pictures, I'm going to post anyway.

Okay, just so I'm understanding. First blood is trial and error? and you have to go from there?

And now for the big one. Do you mean up-down diagonal or do you mean left-right diagonal?

<pre>
/
^ /
| /
| /
/
/ -->
/
/
/
/</pre>

I think that question deserves a prize

Wint · Post by **Wint** » Sat Apr 26, 2003 11:39 am

> after you hurt my eyes with those pictures

lol - I guess they could be a bit hurtful. Perhaps the new versions are better (see above).

> First blood is trial and error? and you have to go from there?

For all practical purposes, yes, since Traxx doesn't show the two lattices.

Looking at my matrix diagram, focusing on the dots marking the individual grid points, one color will raise a "square" pyramid and the other color will raise "diamond" pyramid.

This is perhaps the most simplified statement I can make: There are two lattices, offset by one 'unit', all points on one lattice will create "squared" corners and all points on the other lattice will create "diagonal" corners.

I know many people are reading my words and going:

Edited by Winterkill (26-04-2003)

Post by **Phineus** » Sat Apr 26, 2003 12:28 pm

> square pyramids vs diamond pyramids

I wish I knew this stuff a long time ago. It's good to know.

> I know many people are reading my words and going ...

It's been one of those weeks. At least you can always claim you didn't start it.

Malibu350 · Post by **Malibu350** » Sat Apr 26, 2003 12:35 pm

It's perfectly clear Wint, I envisioned a map but didn't quite know how to display it, yours is very well done, my attempt is kinda hard to read but if you look closely the intersections with the black dots represent the diamond sloped area's and the white dots represent the square sharp cornered zones...

<IMG SRC="http://mtm2.com/~malibu350/images/mtmgbbs/traxxgrid.gif">

hope this helps J

Post by **Phineus** » Sat Apr 26, 2003 12:45 pm

Oh stop it, lol

Wint · Post by **Wint** » Sun Apr 27, 2003 5:26 pm

>> I wish I knew this stuff a long time ago. It's good to know.

Indeed, agreed.

>> my attempt is kinda hard to read but if you look closely...

lol

On a similar note, after posting I realized my blue and yellow grid could teach people how to see stereograms. If you look at it the right way the blue and yellow grids merge and appear 'white'. Perhaps I'll say more later - stereograms are cool.

SLO_HotShoe · Post by **SLO_HotShoe** » Wed Apr 30, 2003 12:36 pm

I've seen this before in some corners. To get away from from i moved corner one square one way or the other to smooth the corner out. But never knew why it did that.