Z buffering is a better rendering technique compared to z sorting, since it can render intersecting 3D objects.
Say, I have an Array containing two Object instances as following:
{v1:new Vector3D(0, 0, 0), v2:new Vector3D(100, 0, 0), v3:new Vector3D(100, 0, 100)}
{v1:new Vector3D(0, 100, 50), v2:new Vector3D(100, 100, 50), v3:new Vector3D(100, 0, 100)}
Those are two Object instances, each containing three Vector3D instances that represent the three vertices of a triangle.
I'll use Matrix3D.transformVector() and Vector3D.project() to draw the triangles with the graphics property of the stage.
When under such circumstances without any sprites created, how can I use Z buffering to draw out each pixel?
I'm with you. I miss z-buffering in pure AS3. At this point there is no z buffering provided for Flash/ActionScript-3. Your current options are:
Reordering sprites
Culling
File a request about z-buffering to Abobe
I'm going to provide two links which are fairly enough to pick up the logic behind z-sorting:
http://www.infiniteturtles.co.uk/blog/fast-sorting-in-as3
http://www.simppa.fi/blog/the-fastest-way-to-z-sort-and-handle-objects-in-as3/
These are well described articles so won't be too hard to understand the idea. Even the source codes is provided.
Related
Question
How can I optimally get the list of vertices for the 3d shape (a convex hull) formed by a set of intersecting planes in 3d space that contains all feasible solutions. Assuming that a 3d shape is formed by the intersection of the planes?
Is there a name for the algorithm I'm seeking for? My background in this problem space is not very good and a nudge in the right direction would satisfy as an answer.
Background
I have a list of planes in the form of A, B, C, d that follow the form Ax + By + Cz - d = 0 and I want to determine the list of vertices formed by the intersection of the planes (-d for the sake of implementation details, I don't want the minus sign to be absorbed as part of the constant). Once I have a good solution I want to create a program for it.
Plane Data
1, 0, 0, 3.3927
1, 0, 0, -3.5354
0, 1, 0, -1.8034
0, 1, 0, 5.1248
0, 0, 1, 0.8506
0, 0, 1, 2.3506
Visualization of planes
Attempt
My intuition tells me that I should determine plane, plane intersection -> line, line intersection -> point, for every plane intersection, but I feel as if this is just the naive/brute force way of doing what I need. Is there perhaps a faster way or a specific algorithm of doing this especially as the number of planes approaches 10, 100, ..., n planes?
reference: https://math.stackexchange.com/questions/475953/how-to-calculate-the-intersection-of-two-planes
My googling so far has led me to think about using Cramer's rule, to help the issue with a more general solution, but it seems rather iterative because I can't just put in all 6 planes in at the same time. At a glance it seems I would have to do some sorting to get the list of planes that intersect with each other. The other thing is that Cramer's rule breaks down a bit and I would have to do a lot of edge case catching to ensure that I can get things working, EX: if I have two planes in 3d space.
reference: https://github.com/guiriosoficial/CramersRule
I have one SpriteBatch in my game, between whose batch.begin() and batch.end() I draw...
a large static background image
several game sprites
I want to clip the area in which the sprites are seen, which I've read is done using ScissorStack.
The problem is that ScissorStack appears to clip the entire SpriteBatch that's sent to the GPU. The result is that it clips my game sprites and the background image.
Question:
Must I have two separate batch.begin() and batch.end() cycles, one without clipping for the background, and another with clipping for the sprites? Or is there a way of clipping just the sprites without using ScissorStack?
If the former, then isn't it rather expensive flushing the SpriteBatch twice as many times simply in order to clip a few sprites, or is it really nothing to worry about in terms of performance?
Related question:
The calculateScissors() method in the latest source code has more parameters than I've seen documented anywhere...
calculateScissors(camera, viewportX, viewportY, viewportWidth, viewportHeight, batchTransform, area, scissor)
What is the purpose of the viewportX, viewportY, viewportWidth, viewportHeight when they appear to be duplicating the camera's viewport and area information, and are not mentioned in any docs?
Basically, I'm really confused... even after (or especially after!) testing the behaviour of different values for each of these parameters.
Any advice sought.
Instead of using a ScissorStack I resorted to using using glScissor to get the results I needed.
#Override
public void render(float delta) {
GameStage.INSTANCE.act(Gdx.graphics.getDeltaTime());
GameStage.INSTANCE.setViewport(GameGeometry.width, GameGeometry.height,
true);
GameStage.INSTANCE.getCamera().translate(
-GameStage.INSTANCE.getGutterWidth(),
-GameStage.INSTANCE.getGutterHeight(), 0);
Gdx.gl.glScissor(
(int) GameStage.INSTANCE.getGutterWidth() * 2,
(int) GameStage.INSTANCE.getGutterHeight(),
(int) Gdx.graphics.getWidth()
- (int) (GameStage.INSTANCE.getGutterWidth() * 4),
(int) Gdx.graphics.getHeight());
Gdx.gl.glDisable(GL10.GL_SCISSOR_TEST);
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
Gdx.gl.glEnable(GL10.GL_SCISSOR_TEST);
GameStage.INSTANCE.draw();
}
Hope this helps.
I am making an achtung die kurve-like game in AS3.0. So far I've done the movements of the 4 different players, and it works alright.
I am now to make collision detection, in order to test if a 'worm'-so to speak, is colliding with eachother or its own tail.
As I understand it, if I use hitTestObject(); it will use the registration area of the whole object, which would be a huge problem, seeing since this registration makes a 4-sided registration that contains all of the object. So if this is used, it will 'collide' just by entering this rectangle instead of hitting the actual worm. Is this correctly understood?
I've been looking through different methods of collision detection, and can't seem to find an optimal one for my project.
My thought were to check if the 'worms' are drawing their new sprites on a white background. if they aren't, then it must have hit something.
You can see how I used my code here: code in .as format linked to an .fla file
Sorry for my ill-formulated question, hope it makes somewhat sense.
Any help is greatly appreciated!!
Best regards - Jesper
Try this function if you want a Pixel Perfect Collision Detection with efficient CPU usage:
trace("Collided: " + (areaOfCollision(mc1, mc2) != null));
trace("Where: " + areaOfCollision(mc1, mc2));
function areaOfCollision(object1:DisplayObject, object2:DisplayObject, tolerance:int = 255):Rectangle {
if (object1.hitTestObject(object2)) {
var limits1:Rectangle = object1.getBounds(object1.parent);
var limits2:Rectangle = object2.getBounds(object2.parent);
var limits:Rectangle = limits1.intersection(limits2);
limits.x = Math.floor(limits.x);
limits.y = Math.floor(limits.y);
limits.width = Math.ceil(limits.width);
limits.height = Math.ceil(limits.height);
if (limits.width < 1 || limits.height < 1) return null;
var image:BitmapData = new BitmapData(limits.width, limits.height, false);
var matrix:Matrix = object1.transform.concatenatedMatrix;
matrix.translate(-limits.left, -limits.top);
image.draw(object1, matrix, new ColorTransform(1, 1, 1, 1, 255, -255, -255, tolerance));
matrix = object2.transform.concatenatedMatrix;
matrix.translate(-limits.left, -limits.top);
image.draw(object2, matrix, new ColorTransform(1, 1, 1, 1, 255, 255, 255, tolerance), BlendMode.DIFFERENCE);
var intersection:Rectangle = image.getColorBoundsRect(0xFFFFFFFF, 0xFF00FFFF);
if (intersection.width == 0) return null;
intersection.offset(limits.left, limits.top);
return intersection;
}
return null;
}
After a successful preliminary hitTestObject(), this function backgroundly takes a snapshot from the shapes of both objects painted with different colors each, then overlays them intersecting the colors on a new one, returning the Rectangle of the resulting shape. So cool.
To learn more about Pixel Perfect Collision Detection you can google Collision Detection followed by one of these names: "The ActionScript Man", "Troy Gilbert", "Boulevart (wim)", "Grant Skinner (gSkinner)" or "Senocular". Those guys are awesome AS3 references by the way.
The problem you discribe is a very common problem for collission detection because the object has a set width and height and therefor defines a rectangle as the object.
There is a solution however to make a colission detection system on pixel level I have found this on the official site and this made me able to make collission detection for bitmaps on pixel level.
http://help.adobe.com/en_US/ActionScript/3.0_ProgrammingAS3/WS5b3ccc516d4fbf351e63e3d118a9b90204-7d55.html
hope it helps you out in the same way.
Looking at the screenshots of that game, I think the best model would be to describe each worm as a chain of circles. Then divide the world/level in a grid with cells somewhat larger than the circle radii.
The collision check would then be:
clear grid
place each circle into the 1 or more grid cells it falls in
iterate over all cells, for each cell:
for each pair of circles (partially) in this cell, check if they intersect. If they do; collision.
Note that this may result in more than 1 collision occurrence between circle A and B, so you'd also need to check that to avoid duplicates.
Step 1 and 2 can be optimized by not clearing the grid, and instead of step 2, updating each circle's cell after it moves. If you size your cells like 5x the size of a circle, a circle can stay in the same cell for a few frames, avoiding excessive add/remove operations.
I'm doing something similar in a project of mine right now, except with space ships! My grid cells are currently 256x256 (too big for your project I think) and my units have radii of about 20.
I can't figure how to make drawImage work... It just does nothing (except that it throws an exception with an undefined description) :
layerCtx.globalAlpha = 0,2; // same thing with this line commented
layerCtx.drawImage(cvs, 0 , 0);
I have 2 canvas, one is a layer and the other is for drawing using the mouse. I want to save what the user has drawn on the first canvas to the layer and apply opacity...
I won't give you all the code but you have to know that the following code works :
layerCtx.putImageData(ctx.getImageData(0, 0, 800, 500), 0, 0);
but I can't use opacity with the previous, so as it is advised in other stackoverflow.com related questions, I'd like to use drawImage with a canvas element.
ctx is the context for my canvas cvs,
layerCtx is the context fort my canvas layer
You're gonna hate this: You wrote 0,2 instead of 0.2. That's why it isn't working.
I know a comma is used as a decimal in a lot of European countries, but 0.2 is what its gotta be for this.
Working example to check your code by:
http://jsfiddle.net/zC4Wh/
With this toolbox I was performing calibration of my camera.
However the toolbox outputs results in matrix form, and being a noob I don't really understand mathy stuff.
The matrix is in the following form.
Where R is a rotation matrix, T is a translation vector.
And these are the results I got from the toolbox. It outputs values in pixels.
-0.980755 -0.136184 -0.139905 217.653207
0.148552 -0.055504 -0.987346 995.948880
0.126695 -0.989128 0.074666 371.963957
0.000000 0.000000 0.000000 1.000000
Using this data can I know how much my camera is rotated and distance of it from the calibration object?
The distance part is easy. The translation from the origin is given by the first three numbers in the rightmost column. This represents the translation in the x, y, and z directions respectively. In your example, the camera's position p = (px, py, pz) = (217.653207, 995.948880, 371.963957). You can take the Euclidean distance between the camera's location and the location of the calibration object (cx, cy, cz). That is it would just be sqrt( (px-cx)2 + (py-cy)2 + (pz-cz)2 )
The more difficult part regards the rotation which is captured in the upper left 3x3 elements of the matrix. Without knowing exactly how they arrived at this, you're somewhat out of luck. That is, it's not easy to convert that back to Euler Angles, if that's what you want. However, you can transform those elements into a Quaternion Rotation which will give you the unique unit vector and angle to rotate the camera to that orientation. The specifics of the computation are provided here. Once you have the Quaternion rotation, you can easily apply it to the vectors n = (0, 0, 1), up = (0, 1, 0) and right = (1, 0, 0) to get the normal (direction the camera is pointed), up and right vectors. The right vector is only useful if you are interested in slewing the camera left or right from its current position.
I'm guessing the code uses the 'standard' formation - then you will find more details in the opencv library docs or their book.