I'm quite new to XNA so excuse me if I ask a 'silly' question but I couldn't find an answer.
I have a problem with the terrain rendered from a heightmap: the terrain I get is too small, I need something larger for my game but I'd like to keep the heigh tdata updated - so I can check for collisions later. (height data being a 2 dimensional array which holds the heights of each point - in my program it's called 'dateInaltime').
The problem is that if I modify the scale of the terrain, the collision checker will use the old values (from the original/small terrain) so I'll get wrong collision points.
My terrain class looks like this.
How can I make the terrain larger but also extend the height data array?
Change this part:
vertex[x + y * lungime].Position = new Vector3(x, dateInaltime[x, y], -y);
to:
vertex[x + y * lungime].Position = new Vector3(x, dateInaltime[x, y], -y) * new Vector3(10);
It should separate the vertices by a scale of 10 (or whatever number you choose).
Related
I want to detect pixel-perfect collisions between 2 sprites.
I use the following function which I have found online, but makes total sense to me.
static bool PerPixelCollision(Sprite a, Sprite b)
{
// Get Color data of each Texture
Color[] bitsA = new Color[a.Width * a.Height];
a.Texture.GetData(0, a.CurrentFrameRectangle, bitsA, 0, a.Width * a.Height);
Color[] bitsB = new Color[b.Width * b.Height];
b.Texture.GetData(0, b.CurrentFrameRectangle, bitsB, 0, b.Width * b.Height);
// Calculate the intersecting rectangle
int x1 = (int)Math.Floor(Math.Max(a.Bounds.X, b.Bounds.X));
int x2 = (int)Math.Floor(Math.Min(a.Bounds.X + a.Bounds.Width, b.Bounds.X + b.Bounds.Width));
int y1 = (int)Math.Floor(Math.Max(a.Bounds.Y, b.Bounds.Y));
int y2 = (int)Math.Floor(Math.Min(a.Bounds.Y + a.Bounds.Height, b.Bounds.Y + b.Bounds.Height));
// For each single pixel in the intersecting rectangle
for (int y = y1; y < y2; ++y)
{
for (int x = x1; x < x2; ++x)
{
// Get the color from each texture
Color colorA = bitsA[(x - (int)Math.Floor(a.Bounds.X)) + (y - (int)Math.Floor(a.Bounds.Y)) * a.Texture.Width];
Color colorB = bitsB[(x - (int)Math.Floor(b.Bounds.X)) + (y - (int)Math.Floor(b.Bounds.Y)) * b.Texture.Width];
if (colorA.A != 0 && colorB.A != 0) // If both colors are not transparent (the alpha channel is not 0), then there is a collision
{
return true;
}
}
}
//If no collision occurred by now, we're clear.
return false;
}
(all the Math.floor are useless, I copied this function from my current code where I'm trying to make it work with floats).
It reads the color of the sprites in the rectangle portion that is common to both sprites.
This actually works fine, when I display the sprites at x/y coordinates where x and y are int's (.Bounds.X and .Bounds.Y):
View an example
The problem with displaying sprites at int's coordinates is that it results in a very jaggy movement in diagonals:
View an example
So ultimately I would like to not cast the sprite position to int's when drawing them, which results in a smooth(er) movement:
View an example
The issue is that the PerPixelCollision works with ints, not floats, so that's why I added all those Math.Floor. As is, it works in most cases, but it's missing one line and one row of checking on the bottom and right (I think) of the common Rectangle because of the rounding induced by Math.Floor:
View an example
When I think about it, I think it makes sense. If x1 is 80 and x2 would actually be 81.5 but is 81 because of the cast, then the loop will only work for x = 80, and therefore miss the last column (in the example gif, the fixed sprite has a transparent column on the left of the visible pixels).
The issue is that no matter how hard I think about this, or no matter what I try (I have tried a lot of things) - I cannot make this work properly. I am almost convinced that x2 and y2 should have Math.Ceiling instead of Math.Floor, so as to "include" the last pixel that otherwise is left out, but then it always gets me an index out of the bitsA or bitsB arrays.
Would anyone be able to adjust this function so that it works when Bounds.X and Bounds.Y are floats?
PS - could the issue possibly come from BoxingViewportAdapter? I am using this (from MonoExtended) to "upscale" my game which is actually 144p.
Remember, there is no such thing as a fractional pixel. For movement purposes, it completely makes sense to use floats for the values and cast them to integer pixels when drawn. The problem is not in the fractional values, but in the way that they are drawn.
The main reason the collisions are not appearing to work correctly is the scaling. The colors for the new pixels in between the diagonals get their colors by averaging* the surrounding pixels. The effect makes the image appear larger than the original, especially on the diagonals.
*there are several methods that may be used for the scaling, bi-cubic and linear are the most common.
The only direct(pixel perfect) solution is to compare the actual output after scaling. This requires rendering the entire screen twice, and requires the scale factor more computations. (not recommended)
Since you are comparing the non-scaled images your collisions appear to be off.
The other issue is movement speed. If you are moving faster than one pixel per Update(), detecting per pixel collisions is not enough, if the movement is to be restricted by the obstacle. You must resolve the collision.
For enemies or environmental hazards your original code is sufficient and collision resolution is not required. It will give the player a minor advantage.
A simple resolution algorithm(see below for a mathematical solution) is to unwind the movement by half, check for collision. If it is still colliding, unwind the movement by a quarter, otherwise advance it by a quarter and check for collision. Repeat until the movement is less than 1 pixel. This runs log of Speed times.
As for the top wall not colliding perfectly: If the starting Y value is not a multiple of the vertical movement speed, you will not land perfectly on zero. I prefer to resolve this by setting the Y = 0, when Y is negative. It is the same for X, and also when X and Y > screen bounds - origin, for the bottom and right of the screen.
I prefer to use mathematical solutions for collision resolution. In your example images, you show a box colliding with a diamond, the diamond shape is represented mathematically as the Manhattan distance(Math.Abs(x1-x2) + Math.Abs(y1-y2)). From this fact, it is easy directly calculate the resolution to the collision.
On optimizations:
Be sure to check that the bounding Rectangles are overlapping before calling this method.
As you have stated, remove all Math.Floors, since, the cast is sufficient. Reduce all calculations inside of the loops not dependent on the loop variable outside of the loop.
The (int)a.Bounds.Y * a.Texture.Width and (int)b.Bounds.Y * b.Texture.Width are not dependent on the x or y variables and should be calculated and stored before the loops. The subtractions 'y-[above variable]` should be stored in the "y" loop.
I would recommend using a bitboard(1 bit per 8 by 8 square) for collisions. It reduces the broad(8x8) collision checks to O(1). For a resolution of 144x144, the entire search space becomes 18x18.
you can wrap your sprite with a rectangle and use its function called Intersect,which detedct collistions.
Intersect - XNA
I am trying to make a new tool for the tabletop simulator community based on my "pack up bag". The Packup Bag is a tool that remembers world position and rotation of objects you place inside it, so you can then place them back in the same positions and rotations they came from when "unpacking the bag".
I have been trying to modify this so it spits things out in a relative position and rotation to the bag, instead of using hardcoded world coordinates. The idea here is that players can sit at any location at the table, pick the faction bag they wish to play.. drop it on a known spot marked for them and press the place and it will populate contents of the bag relative to its location.
Now I have gotten some of this worked out... I am able to get the bag to place relative in some ways .. but I am finding it beyond my maths skills to work out the modifications of the transforms.
Basically I have this part working..
The mod understands relative position to the bag
The mod understands relative rotation to the bag
BUT.. the mod dose not understand relative position AND rotation at the same time.... I need someway to modify the position data relative to the rotational data... but can not work out how.
See this video....
https://screencast-o-matic.com/watch/cFiOeYFsyi
As you can see as I move the bag around the object is placed relative to it.... but if I rotate the bag, the object has the correct rotation but I need math to work out the correct position IF it is rotated. You can see it is just getting placed in the same position it was as if there was no rotation... as I haven't worked out how to code it to do this.
Now I have heard of something called "matrix math" but I couldn't understand it. I'm a self taught programmer of only a few months after I started modding TTS.
You can kinda understand what I mean I hope.. In the video example, when I rotate the bag, the object should be placed with the correct rotation but the world position needs to be changed.
See this Example to see relative rotation ....
https://screencast-o-matic.com/watch/cFiOeZFsyq
My code dose this by remembering the self.getPostion() of the bag and the obj.Position() of the object getting packed up.. it then dose a self - obj and stores that value for the X and Y position. It also remembers if it is negative or position and then when placing it uses the self.postion() and adds or subtracts the adjustment value. Same for rotation.
Still I do not know what ot go from here.. I have been kinda hurting my head on this and thought maybe some of you math guys might have a better idea on how to do this.
: TL;DR :
So I have
bag.getPosition() and obj.getRotation()
bag.getRotation(0 and obj.getRotation()
These return (x,y,z}
What math can I use to find the relative position and rotation of the objects to the bag so if I rotate the bag. The objects come out of it in a relative way...
Preferably in LUA.. thank you!
I'd hope you've found the answer by now, but for anyone else finding this page:
The problem is much simpler than what you're suggesting - it's basic right triangle trigonometry.
Refer to this diagram. You have a right triangle with points A, B, and C, where C is the right angle. (For brevity, I'll use abbreviations opp, adj, and hyp.) The bag is at point A, you want the object at point B. You have the angle and distance (angle A and the length of the hyp, respectively), but you need the x,y coordinates of point B relative to point A.
The x coord is the length of adj, and y coord is the length of opp. As shown, the formulas to calculate these are:
cos(angle A) = adj/hyp
sin(angle A) = opp/hyp
solving for the unknowns:
adj = hyp * cos(angle A)
opp = hyp * sin(angle A)
For your specific use, and taking into account the shift in coordinate system x,y,z => x,z,y:
obj_x_offset = distance * math.cos(bag.getRotation().y)
obj_z_offset = distance * math.sin(bag.getRotation().y)
obj_x_position = bag.getPosition().x + obj_x_offset
obj_z_position = bag.getPosition().z + obj_z_offset
Diagram source:
https://www.khanacademy.org/math/geometry/hs-geo-trig/hs-geo-modeling-with-right-triangles/a/right-triangle-trigonometry-review
Circles with outlier
Link to picture I am working with is above. I am working with OpenCV and C#. i have a video running at 30FPS and I am trying to find the circles using the Hough algorithm (varying levels of light in the video mean I have to adapt the parameters on the fly). The picture shows the problem I am having. Depending on how the camera moves, the algorithm may mark a circle where there is none.
What I would like to do is find and disregard these false circles as outliers using the point list the program generates of each circle's center point location (list is below). Basically, I would rather the circle not be displayed if it has a low likelihood of being correct. I was thinking of writing a function that uses the population standard deviation of each circle's location (circles are relatively uniform distance apart in video) and disregarding circles that are more than two or three standard deviations off in that frame.
My biggest limitation is that this calculation needs to be run for each frame so I need to make it as efficient as possible (several things going on in the background which are also consuming CPU cycles). I found a function on Stack Overflow to calculate Standard Deviation which looks like it may work, but it's only for a single value. I need to figure out how to apply it to coordinates or just think of another way to solve the problem. Here is the code and the point list:
public static double StandardDeviation(this IEnumerable<double> values)
{
double avg = values.Average();
return Math.Sqrt(values.Average(v=>Math.Pow(v-avg,2)));
}
List pointList = new List() {new PointF(122.5F, 157.5F),
new PointF(77.5F, 232.5F),
new PointF(167.5F, 237.5F),
new PointF(42.5F, 152.5F),
new PointF(172.5F, 82.5F),
new PointF(212.5F, 162.5F),
new PointF(257.5F, 242.5F),
new PointF(122.5F, 307.5F),
new PointF(87.5F, 82.5F),
new PointF(32.5F, 302.5F),
new PointF(207.5F, 317.5F),
new PointF(347.5F, 247.5F),
new PointF(442.5F, 97.5F),
new PointF(402.5F, 17.5F),
new PointF(137.5F, 7.5F),
new PointF(312.5F, 167.5F),
new PointF(297.5F, 322.5F),
new PointF(397.5F, 172.5F),
new PointF(437.5F, 247.5F),
new PointF(387.5F, 322.5F),
new PointF(352.5F, 87.5F),
new PointF(312.5F, 7.5F),
new PointF(272.5F, 82.5F),
new PointF(222.5F, 7.5F),
new PointF(77.5F, 372.5F),
new PointF(477.5F, 322.5F) };
You want the root mean square distance around the centers of the circles. This answer from the OpenCV QA forum has a simple solution:
Use both x and y coordinates , loop over your points and use this formula :
MEAN_X += pow(x - x0, 2);
MEAN_Y += pow(y - y0, 2);
TOTAL_RMS = sqrt( 1/n * (MEAN_X + MEAN_Y));
x , y : coordinates from image2
x0 , y0: coordinates from image1
n : number of points
Tell me please what values should I set for D3DRS_POINTSCALE_A, D3DRS_POINTSCALE_B, D3DRS_POINTSCALE_С to point sprites scaled just like other objects in the scene. The parameters A = 0 B = 0 and C = 1 (proposed by F. D. Luna) not suitable because the scale is not accurate enough and the distance between the particles (point sprites) can be greater than it should be. If I replace the point sprites to billboards, the scale of the particles is correct, but the rendering is much slower. Help me please because the speed of rendering particles for my task is very important but the precise of their scale is very important too.
Direct3D computes the screen-space point size according to the following formula:
MSDN - Point Sprites I can not understand what values should be set for A, B, C to scaling was correct
P.S. Sorry for my english I'm from Russia
Directx uses this function to determine scaled size of a point:
out_scale = viewport_height * in_scale * sqrt( 1/( A + B * eye_distance + C * (eye_distance^2) ) )
eye_distance is generated by:
eye_position = sqrt(X^2 + Y^2 + Z^2)
So to answer your question:
D3DRS_POINTSCALE_A is the constant
D3DRS_POINTSCALE_B is the Linear element (scales eye_distance) and
D3DRS_POINTSCALE_C is the quadratic element (scales eye_distance squared).
How to make a 2d world with fixed size, which would repeat itself when reached any side of the map?
When you reach a side of a map you see the opposite side of the map which merged togeather with this one. The idea is that if you didn't have a minimap you would not even notice the transition of map repeating itself.
I have a few ideas how to make it:
1) Keeping total of 3x3 world like these all the time which are exactly the same and updated the same way, just the players exists in only one of them.
2) Another way would be to seperate the map into smaller peaces and add them to required place when asked.
Either way it can be complicated to complete it. I remember that more thatn 10 years ago i played some game like that with soldiers following each other in a repeating wold shooting other AI soldiers.
Mostly waned to hear your thoughts about the idea and how it could be achieved. I'm coding in XNA(C#).
Another alternative is to generate noise using libnoise libraries. The beauty of this is that you can generate noise over a theoretical infinite amount of space.
Take a look at the following:
http://libnoise.sourceforge.net/tutorials/tutorial3.html#tile
There is also an XNA port of the above at: http://bigblackblock.com/tools/libnoisexna
If you end up using the XNA port, you can do something like this:
Perlin perlin = new Perlin();
perlin.Frequency = 0.5f; //height
perlin.Lacunarity = 2f; //frequency increase between octaves
perlin.OctaveCount = 5; //Number of passes
perlin.Persistence = 0.45f; //
perlin.Quality = QualityMode.High;
perlin.Seed = 8;
//Create our 2d map
Noise2D _map = new Noise2D(CHUNKSIZE_WIDTH, CHUNKSIZE_HEIGHT, perlin);
//Get a section
_map.GeneratePlanar(left, right, top, down);
GeneratePlanar is the function to call to get the sections in each direction that will connect seamlessly with the rest of your world.
If the game is tile based I think what you should do is:
Keep only one array for the game area.
Determine the visible area using modulo arithmetics over the size of the game area mod w and h where these are the width and height of the table.
E.g. if the table is 80x100 (0,0) top left coordinates with a width of 80 and height of 100 and the rect of the viewport is at (70,90) with a width of 40 and height of 20 you index with [70-79][0-29] for the x coordinate and [90-99][0-9] for the y. This can be achieved by calculating the index with the following formula:
idx = (n+i)%80 (or%100) where n is the top coordinate(x or y) for the rect and i is in the range for the width/height of the viewport.
This assumes that one step of movement moves the camera with non fractional coordinates.
So this is your second alternative in a little bit more detailed way. If you only want to repeat the terrain, you should separate the contents of the tile. In this case the contents will most likely be generated on the fly since you don't store them.
Hope this helped.