2d – Page 2 – Tarik Billa

Converting 3D position to 2d screen position [r69!]

September 6, 2023 by Tarik

I’ve written for my project the following function; it receives an THREE.Object3D instance and a camera as a parameters and returns the position on the screen. function toScreenPosition(obj, camera) { var vector = new THREE.Vector3(); var widthHalf = 0.5*renderer.context.canvas.width; var heightHalf = 0.5*renderer.context.canvas.height; obj.updateMatrixWorld(); vector.setFromMatrixPosition(obj.matrixWorld); vector.project(camera); vector.x = ( vector.x * widthHalf ) + widthHalf; … Read more

Android: looking for a drawArc() method with inner & outer radius

September 4, 2023 by Tarik

You can do this: Paint paint = new Paint(); final RectF rect = new RectF(); //Example values rect.set(mWidth/2- mRadius, mHeight/2 – mRadius, mWidth/2 + mRadius, mHeight/2 + mRadius); paint.setColor(Color.GREEN); paint.setStrokeWidth(20); paint.setAntiAlias(true); paint.setStrokeCap(Paint.Cap.ROUND); paint.setStyle(Paint.Style.STROKE); canvas.drawArc(rect, -90, 360, false, paint); The key is in paint.setStyle(Paint.Style.STROKE);, it crops the arc’s center with the stroke that you define in … Read more

How to extract part of this image in Java? [closed]

August 23, 2023 by Tarik

If the sprites area read into a BufferedImage, the getSubimage method can be used to get a subimage of the sprite sheet. The getSubimage method will take the x, y, and the width and height of the desired subimage, so the desired sprite can be obtained. Since most of the sprites seem to be the … Read more

2D engines for JavaScript [closed]

August 18, 2023 by Tarik

There isn’t one right now and I would go on to say that there may never be one in the same way that there is jQuery, for the simple fact that most (commercial) games are going to want to be mercilessly performant, which means using as little extra cruft as possible, and many of these … Read more

How to test if a line segment intersects an axis-aligned rectange in 2D?

August 4, 2023 by Tarik

The original poster wanted to DETECT an intersection between a line segment and a polygon. There was no need to LOCATE the intersection, if there is one. If that’s how you meant it, you can do less work than Liang-Barsky or Cohen-Sutherland: Let the segment endpoints be p1=(x1 y1) and p2=(x2 y2). Let the rectangle’s … Read more

Resources for 2d game physics [closed]

July 27, 2023 by Tarik

Here are some resources I assembled a few years ago. Of note is the Verlet Integration. I am also including links to some open source and commercial physics engines I found at that time. There is a stackoverflow article on this subject here: 2d game physics? Physics Methods Verlet Integration (Wikipedia Article) Advanced Character Physics … Read more

Projecting 3D points to 2D plane [closed]

June 15, 2023 by Tarik

If you have your target point P with coordinates r_P = (x,y,z) and a plane with normal n=(nx,ny,nz) you need to define an origin on the plane, as well as two orthogonal directions for x and y. For example if your origin is at r_O = (ox, oy, oz) and your two coordinate axis in … Read more

Perpendicular on a line from a given point

June 10, 2023 by Tarik

I solved the equations for you: k = ((y2-y1) * (x3-x1) – (x2-x1) * (y3-y1)) / ((y2-y1)^2 + (x2-x1)^2) x4 = x3 – k * (y2-y1) y4 = y3 + k * (x2-x1) Where ^2 means squared

Random points inside a parallelogram

May 15, 2023 by Tarik

The question by the OP is a bit ambiguous so the question I will answer is: How to generate a point from a uniform distribution within an arbitrary quadrilateral, which is actually a generalization of How to generate a point from a uniform distribution within an arbitrary (convex) polygon. The answer is based on the … Read more

Changing the Coordinate System in LibGDX (Java)

March 31, 2023 by Tarik

If you use a Camera (which you should) changing the coordinate system is pretty simple: camera= new OrthographicCamera(Gdx.graphics.getWidth(), Gdx.graphics.getHeight()); camera.setToOrtho(true, Gdx.graphics.getWidth(), Gdx.graphics.getHeight()); If you use TextureRegions and/or a TextureAtlas, all you need to do in addition to that is call region.flip(false, true). The reasons we use y-up by default (which you can easily change as … Read more