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  • Isometric Movement in Javascript In the DOM

    - by deep
    I am creating a game using Javascript. I am not using the HTML5 Canvas Element. The game requires both side view controlles, and Isometric controls, hence the movementMode variable. I have got the specific angles, but I am stuck on an aspect of this. https://chillibyte.makes.org/thimble/movement function draw() { if (keyPressed) { if (whichKey == keys.left) { move(-1,0) } if (whichKey == keys.right) { move(1,0) } if (whichKey == keys.up) { move(0,-1) } if (whichKey == keys.down) { move(0,1) } } } This gives normal up, down , left, and right. i want to refactor this so that i can plugin two variables into the move() function, which will give the movement wanted. Now for the trig. /| / | / | y / | /a___| x Take This Right angled Triangle. given that x is 1, y must be equal to tan(a) That Seems right. However, when I do Math.tan(45), i get a number similar to 1.601. Why? To Sum up this question. I have a function, and i need a function which will converts an angle to a value, which will tell me the number of pixels that i need to go up by, if i only go across 1. Is it Math.tan that i want? or is it something else?

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  • Android threads trouble wrapping my head around design

    - by semajhan
    I am having trouble wrapping my head around game design. On the android platform, I have an activity and set its content view with a custom surface view. The custom surface view acts as my panel and I create instances of all classes and do all the drawing and calculation in there. Question: Should I instead create the instances of other classes in my activity? Now I create a custom thread class that handles the game loop. Question: How do I use this one class in all my activities? Or do I have to create a separate thread each time? In my previous game, I had multiple levels that had to create an instance of the thread class and in the thread class I had to set constructor methods for each separate level and in the loop use a switch statement to check which level it needs to render and update. Sorry if that sounds confusing. I just want to know if the method I am using is inefficient (which it probably is) and how to go about designing it the correct way. I have read many tutorials out there and I am still having lots of trouble with this particular topic. Maybe a link to a some tutorials that explain this? Thanks.

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  • Detecting Units on a Grid

    - by hammythepig
    I am making a little turn based strategy game in pygame, that uses a grid system as the main map to hold all the characters and the map layout. (Similar to Fire Emblem, or Advance Wars) I am trying to determine a way to quickly and efficiently (i.e. without too much of a slow down) check if there are any characters within a given range of the currently selected character. So to illustrate: O = currently selected character X = squares within range Range of 1: X X O X X Range of 2: X X X X X X O X X X X X X Range of 3: X X X X X X X X X X X X O X X X X X X X X X X X X Now I have to tell the user who is in range, and I have to let the user choose who to attack if there are multiple enemies in range. If I have a 5x5 grid, filled with " " for empty and numbers for the characters: [ ][ ][ ][ ][4] [ ][1][ ][ ][ ] [ ][ ][ ][ ][ ] [ ][ ][2][3][ ] [ ][ ][ ][ ][ ] Depending on which character the user selects, I would like to show the user which other characters are in range. So if they all had a range of 3: 1 can hit 2 2 can hit 1 or 3 3 can hit 2 4 cannot hit anyone. So, How do I quickly and/or efficiently run though my grid and tell the user where the enemies are? PS- As a bonus, if someone could give an answer that could also work for a minimum distance type range, I would give them a pat on the back and a high five, should they ever travel to Canada and we ever meet in life. For example: Range of 3 to 5: (- is out of range) X X X X X X X X X X X X - X X X X X X - - - X X X X X X - - O - - X X X X X X - - - X X X X X X - X X X X X X X X X X X X

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  • Torque2D, Class vs Datablock

    - by Max Kielland
    I'm scripting my first game with Torque2D and have not fully understood the difference between "Class" and Datablock. To me it seems like Datablock is similar to a struct in C/C++ or a Record in Pascal. If I create Datablocks with new, are they instantiated in the same way as a "Class"? I have a large TileMap and need to attach some information to each Tile. I was thinking to use a Datablock, as a struct, to attach this information to the tile's CustomData property. The two questions are: What is a Datablock and should I use a Datablock or a "Class" for this tile information?

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  • What's the proper way to calculate probability for a card game?

    - by Milan Babuškov
    I'm creating AI for a card game, and I run into problem calculating the probability of passing/failing the hand when AI needs to start the hand. Cards are A, K, Q, J, 10, 9, 8, 7 (with A being the strongest) and AI needs to play to not take the hand. Assuming there are 4 cards of the suit left in the game and one is in AI's hand, I need to calculate probability that one of the other players would take the hand. Here's an example: AI player has: J Other 2 players have: A, K, 7 If a single opponent has AK7 then AI would lose. However, if one of the players has A or K without 7, AI would survive. Now, looking at possible distribution, I have: P1 P2 AI --- --- --- AK7 loses AK 7 survives A7 K survives K7 A survives A 7K survives K 7A survives 7 KA survives AK7 loses Looking at this, it seems that there is 75% chance of survival. However, I skipped the permutations that mirror the ones from above. It should be the same, but somehow when I write them all down, it seems that chance is only 50%: P1 P2 AI --- --- --- AK7 loses A7K loses K7A loses KA7 loses 7AK loses 7KA loses AK 7 survives A7 K survives K7 A survives KA 7 survives 7A K survives 7K A survives A K7 survives A 7K survives K 7A survives K A7 survives 7 AK survives 7 KA survives AK7 loses A7K loses K7A loses KA7 loses 7AK loses 7KA loses 12 loses, 12 survivals = 50% chance. Obviously, it should be the same (shouldn't it?) and I'm missing something in one of the ways to calculate. Which one is correct?

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  • Cocos2d and Body with few collision shapes using chipmunk

    - by Eimantas
    I'm using Cocos2d (0.99.5) with chipmunk physics engine. Currently I'm trying to place a body into space which is combined from few circle shapes. Let's say I have a corresponding sprite image with displays atom (nucleus + 3 electrons around it. Something like this without orbit lines). In it's simplest form - only one circle shape at the center should be enough which would detect collisions from other objects with nucleus. Now I'd like to add other circle shapes for each electron. How can I do that? Now when I add those shapes to the body and add the body into chipmunk space - the shapes (together with the body/sprite) start flickering and spinning with no recognizable pattern (or reason for that matter).

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  • What is wrong with my specular phong shading

    - by Thijser
    I'm sorry if this should be placed on stackoverflow instead however seeing as this is graphics related I was hoping you guys could help me: I'm attempting to write a phong shader and currently working on the specular. I came acros the following formula: base*pow(dot(V,R),shininess) and attempted to implement it (V is the posion of the viewer and R the reflective vector). This gave the following result and code: Vec3Df phongSpecular(const Vec3Df & vertexPos, Vec3Df & normal, const Vec3Df & lightPos, const Vec3Df & cameraPos, unsigned int index) { Vec3Df relativeLightPos=(lightPos-vertexPos); relativeLightPos.normalize(); Vec3Df relativeCameraPos= (cameraPos-vertexPos); relativeCameraPos.normalize(); int DotOfNormalAndLight = Vec3Df::dotProduct(normal,relativeLightPos); Vec3Df reflective =(relativeLightPos-(2*DotOfNormalAndLight*normal))*-1; reflective.normalize(); float phongyness= Vec3Df::dotProduct(reflective,relativeCameraPos); if (phongyness<0){ phongyness=0; } float shininess= Shininess[index]; float speculair = powf(phongyness,shininess); return Ks[index]*speculair; } I'm looking for something more like this:

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  • How was collision detection handled in The Legend of Zelda: A Link to the Past?

    - by Restart
    I would like to know how the collision detection was done in The Legend of Zelda: A Link To The Past. The game is 16x16 tile based, so how did they do the tiles where only a quarter or half of the tile is occupied? Did they use a smaller grid for collision detection like 8x8 tiles, so four of them make one 16x16 tile of the texture grid? But then, they also have true half tiles which are diagonally cut and the corners of the tiles seem to be round or something. If Link walks into tiles corner he can keep on walking and automatically moves around it's corner. How is that done? I hope someone can help me out here.

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  • map data structure in pacman

    - by Sam Fisher
    i am trying to make a pacman game in c# using GDI+, i have done some basic work and i have previously replicated games like copter-it and minesweeper. but i am confused about how do i implement the map in pacman, i mean which datastructure to use, so i can use it for moving AI controlled objects and check collisions with walls. i thought of a 2d array of ints but that didnt make sense to me. looking for some help. thanks.

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  • Making a Background Scrolling in Stacking Game

    - by David Dimalanta
    Hmmm...Is it a good idea to use a LibGDX parallax background for making a stacking game (i.e. PAPA STACKer Lite)? For example, I'm starting to use the blocks to drag-n-drop it. Next, when the next piece reaches the top of the screen, it automatically scrolls to the next one where the available space left. Aside from that, is it also involved with the camera code (Orthographic Camera) that the screen size appeared like 720x1280 but actually it's 1440x2560 for example? And another thing, does the background scrolling have the option to scroll from start to finish and infinite?

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  • How to prevent multiple playing sounds from destroying your hearing?

    - by Rookie
    The problem is that when I play 100 sounds almost at same time, all I hear is noise. It's not very attractive to listen it for 30 minutes straight. I tried to fix this by allowing only 1 sound of each sound type to be played at once. But it still sounds really ugly; eventually my brain keeps hearing only the very end of the shot sounds (or the start of it?), and that gets on my nerves really quickly. Eventually I would just decide to turn off the sounds completely. So is there any point of using sounds in a game like this at all? How does our dear reality handle this problem? If there is a war out there, how does it sound when hundred of men shoot almost at the same times? Edit: Here is how the game sounds currently; there isn't even 100 sounds playing at once, maybe 20? http://www.speedyshare.com/VTBDw/headache.mp3 At the beginning it sounds OK, but then it becomes unbearable! In that audio clip there is allowed only 1 sound to be played at once, so it will stop the previous playing sound when new sound is played. Edit2: And here is same headache but 32 simultaneous sounds allowed to be played at same time: http://www.speedyshare.com/TuWAR/headache-worse.mp3 Quite a torture, eh?

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  • Colorize with a given color a texture

    - by Pacha
    I have a texture and I want to "colorize" it with a given color, lets say cyan (#00ffff) or purple (#800080). What I want to do, is get all the pixel values from the texture, and remove the color and keep the "brightness" and "saturation" and apply to the desired color. There is a tool in GIMP to do this called Colorize (Colors -> Colorize.. while editing), I made an example below. This is will all be done in a shader (GLSL), although this is probably a general algorithm.

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  • How do I determine the draw order in an isometric view flash game?

    - by Gajet
    This is for a flash game, with isometric view. I need to know how to sort object so that there is no need for z-buffer checking when drawing. This might seem easy but there is another restriction, a scene can have 10,000+ objects so the algorithm needs to be run in less than O(n^2). All objects are rectangular boxes, and there are 3-4 objects moving in the scene. What's the best way to do this? UPDATE in each tile there is only object (I mean objects can stack on top of each other). and we access to both map of Objects and Objects have their own position.

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  • How can I test different TV display types for my XBLIG game?

    - by Steve Dunn
    The XBLIG submission check-list says to ensure that all important stuff critical to game-play be visible in the 'TitleSafeArea'. I've received a bug report during play-test of my game (Crazy Balloon Lite) that says parts of my scrolling 2D map are only half visible (i.e. chopped at the left of the screen). I've tested my game myself on a 47" TV and also a 19" VGA monitor, both of which look fine. The bug report says the issue occurs on a standard 20" TV. My question is: without buying different sizes of TVs, is there a way to test what my game will look like on different sized displays?

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  • what is the best way to use loops to detect events while the main loop is running?

    - by yao jiang
    I am making an "game" that has pathfinding using pygame. I am using Astar algo. I have a main loop which draws the whole map. In the loop I check for events. If user press "enter" or "space", random start and end are selected, then animation starts and it will try to get from start to end. My draw function is stupid as hell right now, it works as expected but I feel that I am doing it wrong. It'll draw everything to the end of the animation. I am also detecting events in there as well. What is a better way of implementing the draw function such that it will draw one "step" at a time while checking for events? animating = False; while loop: check events: if not animating: # space or enter press will choose random start/end coords if enter_pressed or space_pressed: start, end = choose_coords route = find_route(start, end) draw(start, end, grid, route) else: # left click == generate an event to block the path # right click == user can choose a new destination if left_mouse_click: gen_event() reroute() elif right_mouse_click: new_end = new_end() new_start = current_pos() route = find_route(new_start, new_end) draw(new_start, new_end, grid, route) # draw out the grid def draw(start, end, grid, route_coord): # draw the end coords color = red; pick_image(screen, color, width*end[1],height*end[0]); pygame.display.flip(); # then draw the rest of the route for i in range(len(route_coord)): # pausing because we want animation time.sleep(speed); # get the x/y coords x,y = route_coord[i]; event_on = False; if grid[x][y] == 2: color = green; elif grid[x][y] == 3: color = blue; for event in pygame.event.get(): if event.type == pygame.MOUSEBUTTONDOWN: if event.button == 3: print "destination change detected, rerouting"; # get mouse position, px coords pos = pygame.mouse.get_pos(); # get grid coord c = pos[0] // width; r = pos[1] // height; grid[r][c] = 4; end = [r, c]; elif event.button == 1: print "user generated event"; pos = pygame.mouse.get_pos(); # get grid coord c = pos[0] // width; r = pos[1] // height; # mark it as a block for now grid[r][c] = 1; event_on = True; if check_events([x,y]) or event_on: # there is an event # mark it as a block for now grid[y][x] = 1; pick_image(screen, event_x, width*y, height*x); pygame.display.flip(); # then find a new route new_start = route_coord[i-1]; marked_grid, route_coord = find_route(new_start, end, grid); draw(new_start, end, grid, route_coord); return; # just end draw here so it wont throw the "index out of range" error elif grid[x][y] == 4: color = red; pick_image(screen, color, width*y, height*x); pygame.display.flip(); # clear route coord list, otherwise itll just add more unwanted coords route_coord_list[:] = [];

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  • Having trouble with projection matrix, need help

    - by Mr.UNOwen
    I'm having trouble with what appears to be the projection matrix. Given a wide enough of a screen, when a cube is on the left and right most edge, the left or right wall will appear stretched to the point that the front face is 1/10 the width of the side. So I do update the screen ratio along with the projection matrix and view port on screen resize, am I safe to assume all the trouble is from the matrix class? Also the cube follows the mouse, but it's only vertically aligned and ahead of the mouse when going left or right from the center of the screen. Perspective function call: * setPerspective * * @param fov: angle in radians * @param aspect: screen ratio w/h * @param near: near distance * @param far: far distance **/ void APCamera::setPerspective(GMFloat_t fov, GMFloat_t aspect, GMFloat_t near, GMFloat_t far) { GMFloat_t difZ = near - far; GMFloat_t *data; mProjection->clear(); //set to identity matrix data = mProjection->getData(); GMFloat_t v = 1.0f / tan(fov / 2.0f); data[_AP_MAA] = v / aspect; data[_AP_MBB] = v; data[_AP_MCC] = (far + near) / difZ; data[_AP_MCD] = -1.0f; data[_AP_MDD] = 0.0f; data[_AP_MDC] = 2.0f * far * near/ difZ; mRatio = aspect; mInvProjOutdated = true; mIsPerspective = true; } and... #define _AP_MAA 0 #define _AP_MAB 1 #define _AP_MAC 2 #define _AP_MAD 3 #define _AP_MBA 4 #define _AP_MBB 5 #define _AP_MBC 6 #define _AP_MBD 7 #define _AP_MCA 8 #define _AP_MCB 9 #define _AP_MCC 10 #define _AP_MCD 11 #define _AP_MDA 12 #define _AP_MDB 13 #define _AP_MDC 14 #define _AP_MDD 15

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  • What is the correct and most efficient approach of streaming vertex data?

    - by Martijn Courteaux
    Usually, I do this in my current OpenGL ES project (for iOS): Initialization: Create two VBO's and one IndexBuffer (since I will use the same indices), same size. Create two VAO's and configure them, both bound to the same Index Buffer. Each frame: Choose a VBO/VAO couple. (Different from the previous frame, so I'm alternating.) Bind that VBO Upload new data using glBufferSubData(GL_ARRAY_BUFFER, ...). Bind the VAO Render my stuff using glDrawElements(GL_***, ...); Unbind the VAO However, someone told me to avoid uploading data (step 3) and render immediately the new data (step 5). I should avoid this, because the glDrawElements call will stall until the buffer is effectively uploaded to VRAM. So he suggested to draw all my geometry I uploaded the previous frame and upload in the current frame what will be drawn in the next frame. Thus, everything is rendered with the delay of one frame. Is this true or am I using the good approach to work with streaming vertex data? (I do know that the pipeline will stall the other way around. Ie: when you draw and immediately try to change the buffer data. But I'm not doing that, since I implemented double buffering.)

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  • How to transform gameObjects in array?

    - by user1764781
    I have an array of available gameObjects in the scene. An array of GO should be transformed according to received floats through UDP connection. I know it is simple, but can't figure it out how to accomplish the transformation an array of GO according to received unique floats for each GO, any help will be appreciated. Here is a transformation floats, it might be helpful I guess: x =ReadSingleBigEndian(data, signalOffset); signalOffset+=4; y= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; z= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; alpha= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; theta= ReadSingleBigEndian(data,signalOffset); signalOffset+=4; phi= ReadSingleBigEndian(data,signalOffset); signalOffset+=4;

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  • How To Scale Canvas In Android

    - by Daniel Braithwaite
    I am writing a android game using Canvas as the way to draw everything, the problem is that when i run it on different android phones the canvas dosn't change size i tried using canvas.scale() but that didn't make a i difference. The code i use for drawing is ... public void draw( Canvas c, int score ) { Obstical2[] obstmp = Queue.toArray(this.o); Coin[] cointmp = QueueC.toArray(this.c); for( int i = 0; i < obstmp.length; i++ ) { obstmp[i].draw(c); } for( int i = 0; i < cointmp.length; i++ ) { cointmp[i].draw(c); } c.drawText(String.format("%d", score ), 20, 50, textPaint); if( isWon && isStarted ) c.drawText("YOU WON", 20, 400, resPaint); else if( isLost && isStarted ) c.drawText("YOU LOST", 20, 400, resPaint); } The function above calls the draw functions for the entity's on the screen, theses function are as follows Draw Function For Obstical : public void draw( Canvas c ) { Log.i("D", "COIN"); coin.draw(c); } Draw Function For Coin : public void draw( Canvas c ) { obstical.draw(c); } How could i make the canvas re-size to it would look the same on any screen ? Cheers Daniel

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  • Need help with a complex 3d scene (using Ogre and bullet)

    - by Matthias
    In my setup there is a box with a hole on one side, and a freely movable "stick" (or bar, tube). This stick can be inserted/moved through the hole into the box. This hole is exactly as wide as the diameter of the stick. In reality, when you would now hold the end of the stick in your hand and move the hand left/right or up/down, the other end of the stick, which is inside the box, would move into the opposite direction of your hand movement (because the stick is affixed at the pivot point where it is entering the box through the hole). (I hope you understand what I mean so far.) Now I need to simulate such a setup in a 3d program. I have already successfully developed an Ogre3d framework for this application, including bullet. But what I don't know is how I can implement in my program what I have described above. This application must include two more features: The scene camera is attached to the end of the stick that is inserted into the box. So when the user would move the mouse (to control "his" end of the stick outside the box), then the camera attached to the stick would move in the opposite direction, as described above. The stick has some length, and the user can push it further into the box, or pull it closer to him again. That means of course that the max. radius on which the end of the stick inside the box can move depends on how far the stick is pushed into the box. Thus, the more the stick is pushed into the box, the larger the max. radius of this end of the stick with the camera will be. I understand this is maybe quite a complex thing, so I don't expect any real source code here. I already have the Ogre and bullet part as said up and running, as well as a camera attached to the stick. This works fine. What I don't know though is how I can simulate the setup described above. Especially the requirement that the stick is affixed at the position of the hole on the box, where it is inserted into the box. Any ideas how I could approach to implement the described setup?

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  • Trying to detect collision between two polygons using Separating Axis Theorem

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • Detect collision from a particular side

    - by Fabián
    I'm making a platform sidescrolling game. All I want to do is to detect if my character is on the floor: function OnCollisionStay (col : Collision){ if(col.gameObject.tag == "Floor"){ onFloor = true; } else {onFloor = false;} } function OnCollisionExit (col : Collision){ onFloor = false; } But I know this isn't the accurate way. If I hit a cube with a "floor" tag, in the air (no matter if with the character's feet or head) I would be able to jump. Is there a way to use the same box collision to detect if I'm touching something from a specific side?

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  • Simulating smooth movement along a line after calculating a collision containing a restitution of zero in 2D

    - by Casey
    [for tl;dr see after listing] //...Code to determine shapes types involved in collision here... //...Rectangle-Line collision detected. if(_rbTest->GetCollisionShape()->Intersects(*_ground->GetCollisionShape())) { //Convert incoming shape to a line. a2de::Line l(*dynamic_cast<a2de::Line*>(_ground->GetCollisionShape())); //Get line's normal. a2de::Vector2D normal_vector(l.GetSlope().GetY(), -l.GetSlope().GetX()); a2de::Vector2D::Normalize(normal_vector); //Accumulate forces involved. a2de::Vector2D intermediate_forces; a2de::Vector2D normal_force = normal_vector * _rbTest->GetMass() * _world->GetGravityHandler()->GetGravityValue(); intermediate_forces += normal_force; //Calculate final velocity: See [1] double Ma = _rbTest->GetMass(); a2de::Vector2D Ua = _rbTest->GetVelocity(); double Mb = _ground->GetMass(); a2de::Vector2D Ub = _ground->GetVelocity(); double mCr = Mb * _ground->GetRestitution(); a2de::Vector2D collision_velocity( ((Ma * Ua) + (Mb * Ub) + ((mCr * Ub) - (mCr * Ua))) / (Ma + Mb)); //Calculate reflection vector: See [2] a2de::Vector2D reflect_velocity( -collision_velocity + 2 * (a2de::Vector2D::DotProduct(collision_velocity, normal_vector)) * normal_vector ); //Affect velocity to account for restitution of colliding bodies. reflect_velocity *= (_ground->GetRestitution() * _rbTest->GetRestitution()); _rbTest->SetVelocity(reflect_velocity); //THE ULTIMATE ISSUE STEMS FROM THE FOLLOWING LINE: //Move object away from collision one pixel to prevent constant collision. _rbTest->SetPosition(_rbTest->GetPosition() + normal_vector); _rbTest->ApplyImpulse(intermediate_forces); } Sources: (1) Wikipedia: Coefficient of Restitution: Speeds after impact (2) Wikipedia: Specular Reflection: Direction of reflection First, I have a system in place to account for friction (that is, a coefficient of friction) but is not used right now (in addition, it is zero, which should not affect the math anyway). I'll deal with that after I get this working. Anyway, when the restitution of either object involved in the collision is zero the object stops as required, but if movement along the same direction (again, irrespective of the friction value that isn't used) as the line is attempted the object moves as if slogging through knee deep snow. If I remove the line of code in question and the object is not push away one pixel the object barely moves at all. All because the object collides, is stopped, is pushed up, collides, is stopped...etc. OR collides, is stopped, collides, is stopped, etc... TL;DR How do I only account for a collision ONCE for restitution purposes (BONUS: but CONTINUALLY for frictional purposes, to be implemented later)

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  • How do I draw a point sprite using OpenGL ES on Android?

    - by nbolton
    Edit: I'm using the GL enum, which is incorrect since it's not part of OpenGL ES (see my answer). I should have used GL10, GL11 or GL20 instead. Here's a few snippets of what I have so far... void create() { renderer = new ImmediateModeRenderer(); tiles = Gdx.graphics.newTexture( Gdx.files.getFileHandle("res/tiles2.png", FileType.Internal), TextureFilter.MipMap, TextureFilter.Linear, TextureWrap.ClampToEdge, TextureWrap.ClampToEdge); } void render() { Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); Gdx.gl.glClearColor(0.6f, 0.7f, 0.9f, 1); } void renderSprite() { int handle = tiles.getTextureObjectHandle(); Gdx.gl.glBindTexture(GL.GL_TEXTURE_2D, handle); Gdx.gl.glEnable(GL.GL_POINT_SPRITE); Gdx.gl11.glTexEnvi(GL.GL_POINT_SPRITE, GL.GL_COORD_REPLACE, GL.GL_TRUE); renderer.begin(GL.GL_POINTS); renderer.vertex(pos.x, pos.y, pos.z); renderer.end(); } create() is called once when the program starts, and renderSprites() is called for each sprite (so, pos is unique to each sprite) where the sprites are arranged in a sort-of 3D cube. Unfortunately though, this just renders a few white dots... I suppose that the texture isn't being bound which is why I'm getting white dots. Also, when I draw my sprites on anything other than 0 z-axis, they do not appear -- I read that I need to crease my zfar and znear, but I have no idea how to do this using libgdx (perhaps it's because I'm using ortho projection? What do I use instead?). I know that the texture is usable, since I was able to render it using a SpriteBatch, but I guess I'm not using it properly with OpenGL.

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  • 2D Collision masks for handling slopes

    - by JiminyCricket
    I've been looking at the example at: http://create.msdn.com/en-US/education/catalog/tutorial/collision_2d_perpixel and am trying to figure out how to adjust the sprite once a collision has been detected. As David suggested at XNA 4.0 2D sidescroller variable terrain heightmap for walking/collision, I made a few sensor points (feet, sides, bottom center, etc.) and can easily detect when these points actually collide with non-transparent portions of a second texture (simple slope). I'm having trouble with the algorithm of how I would actually adjust the sprite position based on a collision. Say I detect a collision with the slope at the sprite's right foot. How can I scan the slope texture data to find the Y position to place the sprite's foot so it is no longer inside the slope? The way it is stored as a 1D array in the example is a bit confusing, should I try to store the data as a 2D array instead? For test purposes, I'm thinking of just using the slope texture alpha itself as a primitive and easy collision mask (no grass bits or anything besides a simple non-linear slope). Then, as in the example, I find the coordinates of any collisions between the slope texture and the sprite's sensors and mark these special sensor collisions as having occurred. Finally, in the case of moving up a slope, I would scan for the first transparent pixel above (in the texture's Ys at that X) the right foot collision point and set that as the new height of the sprite. I'm a little unclear also on when I should make these adjustments. Collisions are checked on every game.update() so would I quickly change the position of the sprite before the next update is called? I also noticed several people mention that it's best to separate collision checks horizontally and vertically, why is that exactly? Open to any suggestions if this is an inefficient or inaccurate way of handling this. I wish MSDN had provided an example of something like this, I didn't know it would be so much more complex than NES Mario style pure box platforming!

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