Fake 3d with only Java 2d

Newbie & Debugging Questions
#1

I’m trying to make an applet using only Java 2d
There’s this one tiny pseudo-element I want to implement
I want to be able to “stretch” a rectangle image in such a way that I can acheive an effect similar to this:

http://blog.muzy.com/wp-content/uploads/2010/05/tile-floor1.png

Now, the math of where the corners of the rectangle go is trivial. I know how to do that. But how can I acheive an effect like this with Java 2D, where I can manipulate each corner?
Is there even a way to do it? I couldn’t find one, but maybe I’m not searching for the right keywords.

Thanks

#2

Couldn’t you just use lines to achieve the effect you are looking for, or is there a real reason it has to be rectangles?

#3

Well, I have pretty floor tile images that I’d like to use

#4

You could try this Graphics.drawPolygon(int[]. int[]. int)
Never mind I read “stretch a rectangle” instead of “stretch a rectangle image”. What about this instead drawImage(Image img, int dx1, int dy1, int dx2, int dy2, int sx1, int sy1, int sx2, int sy2, ImageObserver observer)

#5

That’s a useful function, but I’m not just trying to draw a polygon, I’m trying to draw a polygon with an image. Like the tiles on the floor in the SNES Mario Kart

The tiles on the ground are stretched images in the manner I’m trying to achieve

#6

Ya, I misread your OP :persecutioncomplex: I edited my post when I saw that.

#7

That method does allow me to stretch an image, but only as a rectangle with 90 degree angles, not a quadrilateral that can be used to obtain a 3d effect. It’s the difference between this

and this

#8

What you’re looking for is a perspective transformation, and java2d is not going to give you one of those – it only has affine transforms. So you’re looking at doing it by hand, which I suspect is what they did for that SNES game there.

See this thread: http://www.java-gaming.org/index.php/topic,8803. It mentions JAI having perspective transforms, but JAI is nothing close to real time.

#9

Ah well, I guess I’ll just stick with the solid color polygons. It’ll look good enough.

#10

I haven’t used java2d alot, but would something like this be possible?

Create an Image object ‘ground’ and draw all the ground tiles on this Image.

Create a new Image object ‘groundOnScreen’ and individually map each pixel on ‘groundOnScreen’ to a pixel (or some value based on nearby pixels) on ‘ground’.

I made a quick illustration is paint:

http://www.oyvindbyhring.net/illustration.png

Just mindstorming here, I don’t know if you could actually do this with java2d :x

#11

ah yes “mode 7”

would be really interested to see what you come up with

#12

Oh cool … I also created exactly this many years ago (like 2006).

I pretty much gave it Nintendo GBA registers and a scanline “interrupt” so that you could quite easily put Mode 7 code into it with the same arithmetic as the GBA hardware, it’s tile mode too so if you’d like the code give me a shout and I’ll github it. here it is: https://github.com/keldon85-avasopht/stroll

Edit: Hmm, give me a minute, I’m just creating the repositories, etc. It comes with a demonstration of Tetris, which rotates the background mode 7 style.

p.s. it’s all software rendered.

#13

By using the matrix described on this page
http://chrisjones.id.au/Ellipses/ellipse.html
you can project any image onto any rectangle in 3D space.
I used that technique once in a software renderer that I mentioned in this thread
http://www.java-gaming.org/topics/2d-rendering-but-with-a-3d-coordinate-system/26733/msg/237578/view.html#msg237578

#14

I’d be easy just to do it in software. Each scanline is constant du & dv.

#15

That’s exactly what my code above is. It’s a scanline renderer that imitates the GBA/SNES’s gfx hardware registers so that you can use mode7 code/calculations. The graphics API provides a HBL and VBL callback so that you can do all the types of tricks used for mode7 :slight_smile: Plus it comes with example code that demonstrates mode7 x-axis rotations.

Check it out. And if you want more info in the maths, check out this awesome Mode 7 tutorial.