Java Community | Help. Code. Learn.•2y ago

Rendering a image with Graphics2D based on 4 points

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Kyo-chan•2y ago

And, erm, you have trouble finding a method from Graphics2D that might possibly do exactly that? Ah wait no, 4 points. Okay. I'm not sure either

JavaBot•2y ago

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Defective•2y ago

graphics2d.drawImage(image, x1, y1, x2-x1, y2-y1, null); ? this method takes width and height as the 3rd and 4th argument, so you need to calculate them yourself

Kyo-chan•2y ago

From 4 points there is no reason to believe the points make out a rectangle, yet that method assumes so

Defective•2y ago

oh right My bad

tjoener•2y ago

https://docs.oracle.com/javase/8/docs/api/java/awt/geom/AffineTransform.html This is what you need Have not used the API in forever though Plus starting from points makes it a lot harder

Kyo-chan•2y ago

I suspect that OP would have needed to give more information about their problem. One AffineTransform can't solve the issue for any arbitrary set of points

tjoener•2y ago

yeah no, but, and I'm going on a limb here, he's trying to draw textures to fake cubes as in some sort of minecraft clone 🙂 But afaik, affinetransform and the corresponding graphics2d.drawimage is the only standard thing to get anywhere close to where they want to go. And if it is game related, there should be an affinetransform available already of some sort

dan1st•2y ago

Do these 4 points form a rectangle or are they completely arbitrary?

dan1st•2y ago

If it is (like the black image), you can draw the image starting on the bottom left corner like the red image. For the dx and dy lengths, they are equal to the lengths of the dides of the original rectangle (the blue lengths are equal and the pink lengths are equal). Then, you'd have to rotate it.

Unknown UserOP•2y ago

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dan1st•2y ago

I don't think the image is the problem The problem is more that we don't know whate xactly you want to do

Unknown UserOP•2y ago

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dan1st•2y ago

the proportion being different/stretching wouldn't be much of a problem I think but if the points don't represent a rectangle, it's more difficult

dan1st•2y ago

e.g. can the points be arranged like this?

dan1st•2y ago

or in other words: Is the 4th point created such that the whole thing assembles a rectangle if it'S a parallelogram, you can probably also apply some transformations

The Typhothanian (@always)•2y ago

@hundo I just figured this out for my game over the weekend, so I got you covered. Pic is my work. On the top is a quad, and the inner quad is representing a pixel. This pixel, if the quad was a 20x20 square, would be from 10, 5 to 15, 13. Since the square is 20x20, we need to divide each dimension by 20. So, we have these vars: startX = 0.5 endX = 0.75 startY = 0.25 endY = 0.65 Then, we use a lerp function (a + t * (b - a)) to find the coords on each line. We should have eight. Then, we connect the lines from #0 to #5, #1 to #4, etc. and where the lines intersect is our projected pixel. Now, this isn't an especially efficient method for games, but if you start skipping pixels as the quad gets smaller, it is good enough. However, if you want/are okay with smoothing, then check out LWJGL. There is a method literally for this, but you need some buffer stuff and triangles. Hope this helps.

Unknown UserOP•2y ago

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The Typhothanian (@always)•2y ago

oops @Hunter btw, that took me about a month to figure out (I was messing around with distancing before) so yw

Kyo-chan•2y ago

So the explanation and example don't use 4 points, and when we ask what it is you need you answer you need to adapt to 4 points, but now that you get this you like it.

dan1st•2y ago

if it is that case, you could try https://stackoverflow.com/a/16796687/10871900

Stack Overflow

Draw an Image in arbitrary corners

So i have a normal image. I defined Click- and Drag-Listeners on each corner of the rectangular image. I want to freely transform each of the corners and paint it on the screen. The AffineTransform

Unknown UserOP•2y ago

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dan1st•2y ago

Why?

The Typhothanian (@always)•2y ago

Yes

dan1st•2y ago

tbh I wouldn't be so sure about that

JavaBot•2y ago

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Unknown UserOP•2y ago

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dan1st•2y ago

reduce it to a minimal reproducable example

JavaBot•2y ago

https://stackoverflow.com/help/mcve

dan1st•2y ago

(so that it isn't problematic in any way)

Unknown UserOP•2y ago

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dan1st•2y ago

No I won't run code from random people on the internet and I also don't recommend others to do that what exactly is happening?

Unknown UserOP•2y ago

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dan1st•2y ago

Are you possibly blocking the UI thread?

JavaBot•2y ago

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Unknown UserOP•2y ago

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dan1st•2y ago

Is your code actually executed delayed or does your code execute in time and it's just the rendering?

Unknown UserOP•2y ago

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dan1st•2y ago

How much behind?

Unknown UserOP•2y ago

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dan1st•2y ago

px?

Unknown UserOP•2y ago

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dan1st•2y ago

not milliseconds? I thought behind meant behind in time

Unknown UserOP•2y ago

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dan1st•2y ago

with behind, do you mean it's below than where it should be?

Unknown UserOP•2y ago

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JavaBot•2y ago

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dan1st•2y ago

Can you check whether the tick method is actually executed 100 times per second? i.e. you can add something like

//before the loop
long lastTime = System.currentTimeMillis();
//in loop
long newTime = System.currentTimeMillis();
System.out.println(newTime-lastTime);
lastTime = newTime;

//before the loop
long lastTime = System.currentTimeMillis();
//in loop
long newTime = System.currentTimeMillis();
System.out.println(newTime-lastTime);
lastTime = newTime;

Unknown UserOP•2y ago

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dan1st•2y ago

Is it just the image? What values does that typically print? How much delay is there with rendering?

Unknown UserOP•2y ago

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dan1st•2y ago

looks like you are doing a lot of work compared to the number of ticks How does it change when sleeping for 50ms instead of 10? Does the problem of the drawing being delayed stay the same, does it get worse or does it get better? Also you might want to try using a swing timer instead of Thread.sleep and how much is the drawing delayed?

Unknown UserOP•2y ago

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dan1st•2y ago

you mean the screen is black?

Unknown UserOP•2y ago

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dan1st•2y ago

oh nvm it didn't show properly

Unknown UserOP•2y ago

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dan1st•2y ago

ok you have a square and a line

Unknown UserOP•2y ago

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dan1st•2y ago

what's the issue about that?

Unknown UserOP•2y ago

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dan1st•2y ago

For testing, if you change the Thread.sleep from 10 to 1000 which means you should have a bit less than 1 frame per second Is it always 1 frame behind?

tjoener•2y ago

Also adjust the dt then 🙂

Unknown UserOP•2y ago

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dan1st•2y ago

well ig my goal is to make everything run slower

Unknown UserOP•2y ago

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tjoener•2y ago

do you do move calculation in a separate thread or something? or rendering in a separate thread?

dan1st•2y ago

https://github.com/zivthefire/SAT/blob/master/src/main/java/org/example/Display.java

GitHub

SAT/src/main/java/org/example/Display.java at master · zivthefire/SAT

Contribute to zivthefire/SAT development by creating an account on GitHub.

dan1st•2y ago

What exactly do you mean with moving and then rendering?

Unknown UserOP•2y ago

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dan1st•2y ago

yes

Unknown UserOP•2y ago

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dan1st•2y ago

well calculating the overlap happens one tick after moving, right?

Unknown UserOP•2y ago

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dan1st•2y ago

Like - Tick 1 - move into the object - you render - Tick 2 - You check for collision and move out - you render that's my guess

Unknown UserOP•2y ago

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dan1st•2y ago

is it intended that you don't use the result of isColliding?

Unknown UserOP•2y ago

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dan1st•2y ago

https://github.com/zivthefire/SAT/blob/0acdac4ca664f191dad9a1413244a7f31ceb7198/src/main/java/org/example/OBB.java#L428-L433 You aren't using additionX/additionY here. Is that intended?

GitHub

SAT/src/main/java/org/example/OBB.java at 0acdac4ca664f191dad9a1413...

Contribute to zivthefire/SAT development by creating an account on GitHub.

JavaBot•2y ago

        int additionX = (shortest.x == 0) ? 0 : (shortest.x > 0) ? 1 : -1;
        int additionY = (shortest.y == 0) ? 0 : (shortest.y > 0) ? 1 : -1;
        this.x += shortest.x;
        this.y += shortest.y;
        this.localvelocity = box2.velocity;
        this.localvelocity =box2.velocity;

        int additionX = (shortest.x == 0) ? 0 : (shortest.x > 0) ? 1 : -1;
        int additionY = (shortest.y == 0) ? 0 : (shortest.y > 0) ? 1 : -1;
        this.x += shortest.x;
        this.y += shortest.y;
        this.localvelocity = box2.velocity;
        this.localvelocity =box2.velocity;

Unknown UserOP•2y ago

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dan1st•2y ago

ah ok This this issue happen regardless of where you collide from?

Unknown UserOP•2y ago

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dan1st•2y ago

Unknown UserOP•2y ago

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dan1st•2y ago

Also if you put a System.out.println("collision") or similar before the return true;, is that executed once per collision or multiple tikmes? btw you can remove the previous testing code if you haven't already

Unknown UserOP•2y ago

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dan1st•2y ago

the things with the time changes and the System.out.println with the time difference

Unknown UserOP•2y ago

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dan1st•2y ago

Did you check that?

Unknown UserOP•2y ago

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dan1st•2y ago

Callinjg repaint() twice doesn't change anything, right? Note that from the docs of repaint:

If this component is a lightweight component, this method causes a call to this component's paint method as soon as possible. Otherwise, this method causes a call to this component's update method as soon as possible.

maybe it cannot repaint and "as soon as possible" happens one frame later for some reason? actually no that doesn't seem to be the case you could try debugging the isColliding method and check whether the x/y are actually correct Does the isColliding method actually return true in the same frame as the collision happens? What actually causes the collision? Is the collision caused by moving in tick()? If so, where does that movement happen? oh yeah I think I know why

dan1st•2y ago

you are mvoing here: https://github.com/zivthefire/SAT/blob/0acdac4ca664f191dad9a1413244a7f31ceb7198/src/main/java/org/example/OBB.java#L833-L843

GitHub

SAT/src/main/java/org/example/OBB.java at 0acdac4ca664f191dad9a1413...

Contribute to zivthefire/SAT development by creating an account on GitHub.

JavaBot•2y ago

if(!Static) {

    velocity.add(accleration);


    totalvelocity = Vector2D.add(velocity,localvelocity);

    x += totalvelocity.x;
    y -= totalvelocity.y;

}

if(!Static) {

    velocity.add(accleration);


    totalvelocity = Vector2D.add(velocity,localvelocity);

    x += totalvelocity.x;
    y -= totalvelocity.y;

}

dan1st•2y ago

but you are updating the relative axis here: https://github.com/zivthefire/SAT/blob/0acdac4ca664f191dad9a1413244a7f31ceb7198/src/main/java/org/example/OBB.java#L807-L818

GitHub

SAT/src/main/java/org/example/OBB.java at 0acdac4ca664f191dad9a1413...

Contribute to zivthefire/SAT development by creating an account on GitHub.

JavaBot•2y ago

          if (i == 0) {


              yAxisRelative = v;

          } else if (i == 1) {
              v.reverse();

              xAxisRelative = v;


          }

          if (i == 0) {


              yAxisRelative = v;

          } else if (i == 1) {
              v.reverse();

              xAxisRelative = v;


          }

dan1st•2y ago

before moving in other words, you first update the axis used for collision checking and move afterwards so it uses old information for collision checking take that movement code and try moving it up to the beginning of the tick method .

Unknown UserOP•2y ago

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dan1st•2y ago

ok so the part with the delay works Do you still have the problem of something being 10px off?

Unknown UserOP•2y ago

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JavaBot•2y ago

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Rendering a image with Graphics2D based on 4 points

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