Let's say I have this glutIdleFunc going in the background of an OpenGL scene containing a little creature with multiple, radially arranged legs that "pulsate":
void PulsateLegs(void)
{
lowerLegsRot = (lowerLegsRot + 1)%360;
glutPostRedisplay();
}
...where the lowerLegsRot value is used like this in the display function:
glRotatef((GLfloat)lowerLegsRot, 1.0, 0.0, 0.0);
It's hard to visualize without seeing what the little fellow actually looks like, but it's clear that this function is making the legs spin all the way around repeatedly. I want to limit this spin to a certain range (say, -15 to 50 degrees), and, furthermore, to make the legs go back and forth within the range, like a pendulum.
Since I'm going for a 65 degree swath, I tried just changing "%360" to "%65" as a first step. But this made the legs go way too fast, and I cannot use a lower increment value if I want to use modulus, which only works on ints.
Is there another way to achieve the desired first-step behavior? More importantly, how can I make the legs go back and forth? It's kind of hard to conceptualize with a function that is getting called multiple times (vs. just using a loop structure that takes care of everything, which I tried before I realized this!)
and I cannot use a lower increment value if I want to use modulus, which only works on ints.
The % operator is broken anyway. You should not use integers, but floats, and use the fmod (double) or fmodf (float) function.
Related
If I have two instances called block1 and block2. And they move off the stage. It scrolls down the y position and it respawns back on top. But I don't want the x/y position colliding with the other blocks? I want it to respawn back to position, but I want it randomized but at the same time I don't want it touching each other?
Heres my code:
if (block1.y > stage.stageHeight)
{
block1.y = -550;
block1.x = (Math.floor(Math.random() * (maxNum - minNum + 5)) + minNum);
}
I'm pretty sure I'm calculating the respawn coordinates the wrong way, but I'm not sure how to put it in a random x and y position without colliding with other blocks.
A very simple method can be just to spawn your box, do a collision check, then if collision, remove and respawn and recheck until you find an empty spot where it fits
This is obviously quite inefficient, but is pretty simple to implement quickly if you have some sort of collision detection already working. Keep in mind if there is no spot that it can fit in, then it'll loop forever so you may want to set a max try count or something of that sort.
How fast/well it'll actually work will depend on if the spawn area is pretty sparse or pretty dense, which will increase/decrease the percentage that it'll find a good empty spot the first few times.
There is some room for improvement, going down this path though, such as if your collision detection system gives a minimum translation vector, you could just move the new shape over and use that position to spawn.
Other simple methods could involve keeping track of known occupied positions and adjusting your random range to avoid those values.
I want to make randomized numbers but if they are too close, I want to make it a reroll or make it a number further away from the the other number or try to make it a little more spread out.
I guess I am not sure what exactly I want :/
Thanks in advance
EDIT: So the reason i am making randomized numbers is for spawning positions for units on sides of the screen so i want units to not be too close to each other essentially to make it look better.
I want to make randomized numbers but if they are too close, I want to
make it a reroll or make it a number further away from the the other
number or try to make it a little more spread out.
A random number generator sometimes produces numbers that are near each other.
If you don't want them so close together, maybe what you need is fixed numbers each with a small random perturbation.
Let's say you choose numbers 10, 20, 30, 40, and 50. Then, you run a random number generator that gives you a number between -3 and +3. You add this random number to each one in turn. This produces numbers that aren't uniform, but they're not too close to one another.
If a re-roll would be sufficient, you could just save the previous value, and then on the next iteration, if the difference between the two numbers is too small, call Math.rand() again. Maybe your sample space is too small?
Get random position
If it's not good (too close to some other or what ever) go to step 1.
There you go! You got valid position. :)
...
Or...pre-calculate all valid positions, place them in some array and use rnd function to get array indexes - what array elements will use. That should be the faster solution (if you have huge number of units)...
I have a car object, and I want it to gradually rotate to the direction where the user clicked.
Every frame I did math to calculate the new direction it needs, and it's stored at car.direction. The actual direction is of course in car.rotation.
Now I want to update the rotation every frame until it's equal to the direction. However I tried everything and can't figure out how to do that.
By the way, I'm using FireFly, that is a gameengine built on top of Starling Framework, But I don't think it's relevant.
I would go with Marty's suggestion, use the smallestAngle function to determine which direction you should be rotating. Basically you can move some percentage of the smallestAngle during every frame update until the percentage of that smallestAngle is below some threshold (and have it "snap" the rest of the way).
Something like
//each time this is called it will get 1/4 closer, but never get to 0, hence the need for a threshold avoid paradoxes
//http://en.wikipedia.org/wiki/Zeno's_paradoxes#Dichotomy_paradox
var angleToMove:Number = smallestAngle()/4; //the divide by 4 here means get 1/4 of the angle gap closer each time this function is called, I assume this is on a timer or frame handler, making the 4 greater will make it follow more slowly, making it lower will make it follow more quickly, never reduce to or below 0 unless you want wonkiness
if(angleToMove<someRadianThreshold)
angleToMove = smallestAngle();
//use angleToMove to adjust the current heading/rotation
Basically, I want to get the most common ARGB value that appears in a BitmapData. That is, I want to know which exact pixel colour is the most abundant in the image. I tried going through every pixel of the image and counting whenever a colour that already exists comes up, but that's way too slow, even with relatively small images. Does anybody know a faster method for this, maybe using the BitmapData.histogram() function or something?
Ideally the process should be near instantaneous for images around at least 1000x1000 pixels.
Run through bitmapData.getVector() with a Dictionary to hold numbers, then sort that Dictionary's key-value pairs by value and get the key of maximum.
var v:Vector.<uint>=yourBitmapData.getVector(yourBitmapData.rect);
var d:Dictionary=new Dictionary();
for (var i:int=v.length-1; i>=0;i--) {
if (d[v[i]]) d[v[i]]++; else d[v[i]]=1;
}
var maxkey:String=v[0].toString();
var maxval:int=0;
for (var k:String in d) {
if (d[k]>maxval) {
maxval=d[k];
maxkey=k;
}
}
return parseInt(maxkey); // or just maxkey
I haven't worked with shaders at all, but I think you might be able to get faster results. Looping through pixels is faster at the shader level.
I'd try by creating essentially the same loop in the shader, and paint the entire resulting bitmap with the most used colour and sample that (unless you can get a variable directly out of the shader)
this should be significantly faster
I'm trying to position an image on top of another image based upon the make-up of the smaller image. The smaller image is a cut-out of a larger image and I need it to be positioned exactly on the larger image to make it look like a single image, but allow for separate filters and alphas to be applied. As the images are not simple rectangles or circles, but complex satellite images, I cannot simply redraw them in code. I have quite a few images and therefore do not feel like manually finding the position of each image every and hard setting them manually in actionscript. Is there any way for me to sample a small 5-10 sq. pixel area against the larger image and set the x and y values of the smaller image if a perfect match is found? All the images are in an array and iterating through them has already been set, I just need a way to sample and match pixels. My first guess was to loop the images pixel by pixel right and down, covering the whole bitmap and moving to the next child in the array once a match was found, leaving the matched child where it was when the perfect match was found.
I hope I understood your question correctly.
There may be an option that uses copypixels to achieve what you want. You can use the bitmapdata.rect value to determine the size of the sample you want, and loop through the bigger bitmap using thet rectangle and a moving point. Let's see if I can code this out...
function findBitmapInBitmap(tinyimg:BitmapData, largeimg:BitmapData):Point {
var rect:Rectangle = tinyimg.rect;
var xbound:uint = largeimg.rect.width;
var ybound:uint = largeimg.rect.height;
var imgtest:BitmapData = new BitmapData(tinyimg.rect.width, tinyimg.rect.height);
for (var ypos:uint = 0, y <= ybound, y++) {
for (var xpos:uint = 0, x <= xbound, x++) {
imgtest.copyPixels(largeimg, rect, new Point(xpos, ypos);
if (imgtest.compare(tinyimg) == 0) return new Point(xpos, ypos);
}
}
return new Point(-1,-1); // Dummy value, indicating no match.
}
Something along those lines should work - I'm sure there's room for code elegance and possible optimization. However, it seems like something like this method would be very slow, since you'd have to check each pixel for a match.
There is a better way. Split your big image into layers, and use the blitting technique to composite them at runtime. In your case, you could create a ground texture without satellites, and then create the satellites separately, and use the copyPixels method to place them whereever you want. Google "blitting in as3" to find some good tutorials. I'm currently working on a game project that uses this technique and it's a very good method.
Good luck!
Edit: Forgot to code in a default return statement. Using this method, you'd have to return an invalid point (like (-1,-1)) and check for it outside the function. Alternatively, you could just copy your small bitmap to the big one within the function, which would be much more logical, but I don't know your requirements.
You need to find pixel sequence in the big image. BitmapData.getPixel gives you pixel value. So get first pixel from small image, find it in big image, then continue comparing until you find full match. If you have trouble to code that, feel free to ask.
For the actual comparison, there's BitmapData.compare which returns the number 0 if the BitmapData objects are equivalent.