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• Grid pathfinding with a lot of entities

  - by Vee

  I'd like to explain this problem with a screenshot from a released game, DROD: Gunthro's Epic Blunder, by Caravel Games. The game is turn-based and tile-based. I'm trying to create something very similar (a clone of the game), and I've got most of the fundamentals done, but I'm having trouble implementing pathfinding. Look at the screenshot. The guys in yellow are friendly, and want to kill the roaches. Every turn, every guy in yellow pathfinds to the closest roach, and every roach pathfinds to the closest guy in yellow. By closest I mean the target with the shortest path, not a simple distance calculation. All of this without any kind of slowdown when loading the level or when passing turns. And all of the entities change position every turn. Also (not shown in screenshot), there can be doors that open and close and change the level's layout. Impressive. I've tried implementing pathfinding in my clone. First attempt was making every roach find a path to a yellow guy every turn, using a breadth-first search algorithm. Obviously incredibly slow with more than a single roach, and would get exponentially slower with more than a single yellow guy. Second attempt was mas making every yellow guy generate a pathmap (still breadth-first search) every time he moved. Worked perfectly with multiple roaches and a single yellow guy, but adding more yellow guys made the game slow and unplayable. Last attempt was implementing JPS (jump point search). Every entity would individually calculate a path to its target. Fast, but with a limited number of entities. Having less than half the entities in the screenshot would make the game slow. And also, I had to get the "closest" enemy by calculating distance, not shortest path. I've asked on the DROD forums how they did it, and a user replied that it was breadth-first search. The game is open source, and I took a look at the source code, but it's C++ (I'm using C#) and I found it confusing. I don't know how to do it. Every approach I tried isn't good enough. And I believe that DROD generates global pathmaps, somehow, but I can't understand how every entity find the best individual path to other entities that move every turn. What's the trick? This is a reply I just got on the DROD forums: Without having looked at the code I'd wager it's two (or so) pathmaps for the whole room: One to the nearest enemy, and one to the nearest friendly for every tile. There's no need to make a separate pathmap for every entity when the overall goal is "move towards nearest enemy/friendly"... just mark every tile with the number of moves it takes to the nearest target and have the entity chose the move that takes it to the tile with the lowest number. To be honest, I don't understand it that well.

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• Data-driven animation states

  - by user8363

  I'm trying to handle animations in a 2D game engine hobby project, without hard-coding them. Hard coding animation states seems like a common but very strange phenomenon, to me. A little background: I'm working with an entity system where components are bags of data and subsystems act upon them. I chose to use a polling system to update animation states. With animation states I mean: "walking_left", "running_left", "walking_right", "shooting", ... My idea to handle animations was to design it as a data driven model. Data could be stored in an xml file, a rdbms, ... And could be loaded at the start of a game / level/ ... This way you can easily edit animations and transitions without having to go change the code everywhere in your game. As an example I made an xml draft of the data definitions I had in mind. One very important piece of data would simply be the description of an animation. An animation would have a unique id (a descriptive name). It would hold a reference id to an image (the sprite sheet it uses, because different animations may use different sprite sheets). The frames per second to run the animation on. The "replay" here defines if an animation should be run once or infinitely. Then I defined a list of rectangles as frames. <animation id='WIZARD_WALK_LEFT'> <image id='WIZARD_WALKING' /> <fps>50</fps> <replay>true</replay> <frames> <rectangle> <x>0</x> <y>0</y> <width>45</width> <height>45</height> </rectangle> <rectangle> <x>45</x> <y>0</y> <width>45</width> <height>45</height> </rectangle> </frames> </animation> Animation data would be loaded and held in an animation resource pool and referenced by game entities that are using it. It would be treated as a resource like an image, a sound, a texture, ... The second piece of data to define would be a state machine to handle animation states and transitions. This defines each state a game entity can be in, which states it can transition to and what triggers that state change. This state machine would differ from entity to entity. Because a bird might have states "walking" and "flying" while a human would only have the state "walking". However it could be shared by different entities because multiple humans will probably have the same states (especially when you define some common NPCs like monsters, etc). Additionally an orc might have the same states as a human. Just to demonstrate that this state definition might be shared but only by a select group of game entities. <state id='IDLE'> <event trigger='LEFT_DOWN' goto='MOVING_LEFT' /> <event trigger='RIGHT_DOWN' goto='MOVING_RIGHT' /> </state> <state id='MOVING_LEFT'> <event trigger='LEFT_UP' goto='IDLE' /> <event trigger='RIGHT_DOWN' goto='MOVING_RIGHT' /> </state> <state id='MOVING_RIGHT'> <event trigger='RIGHT_UP' goto='IDLE' /> <event trigger='LEFT_DOWN' goto='MOVING_LEFT' /> </state> These states can be handled by a polling system. Each game tick it grabs the current state of a game entity and checks all triggers. If a condition is met it changes the entity's state to the "goto" state. The last part I was struggling with was how to bind animation data and animation states to an entity. The most logical approach seemed to me to add a pointer to the state machine data an entity uses and to define for each state in that machine what animation it uses. Here is an xml example how I would define the animation behavior and graphical representation of some common entities in a game, by addressing animation state and animation data id. Note that both "wizard" and "orc" have the same animation states but a different animation. Also, a different animation could mean a different sprite sheet, or even a different sequence of animations (an animation could be longer or shorter). <entity name="wizard"> <state id="IDLE" animation="WIZARD_IDLE" /> <state id="MOVING_LEFT" animation="WIZARD_WALK_LEFT" /> </entity> <entity name="orc"> <state id="IDLE" animation="ORC_IDLE" /> <state id="MOVING_LEFT" animation="ORC_WALK_LEFT" /> </entity> When the entity is being created it would add a list of states with state machine data and an animation data reference. In the future I would use the entity system to build whole entities by defining components in a similar xml format. -- This is what I have come up with after some research. However I had some trouble getting my head around it, so I was hoping op some feedback. Is there something here what doesn't make sense, or is there a better way to handle these things? I grasped the idea of iterating through frames but I'm having trouble to take it a step further and this is my attempt to do that.

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• How to show a minimap in a 3d world

  - by Bubblewrap

  Got a really typical use-case here. I have large map made up of hexagons and at any given time only a small section of the map is visible. To provide an overview of the complete map, i want to show a small 2d representation of the map in a corner of the screen. What is the recommended approach for this in libgdx? Keep in mind the minimap must be updated when the currently visible section changes and when the map is updated. I've found SpriteBatch, but the warning label on it made me think twice: A SpriteBatch is a pretty heavy object so you should only ever have one in your program. I'm not sure i'm supposed to use the one SpriteBatch that i can have on the minimap, and i'm also not sure how to interpret "heavy" in this context. Another thing to possibly keep in mind is that the minimap will probably be part of a larger UI...is there any way to integrate these two?

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• Managing game state / 'what to update' within an XNA game 'screen'

  - by codinghands

  Note - having read through other GDev questions suggested when writing this question I'm confident this isn't a dupe. Of course, it's 3am and I'm likely wrong, so please mod as such if so. I'm trying to figure out how best to manage state within my game screens - please bare with me though! At the moment I'm using a heavily modified version of the fantastic game state management example on the XNA site available here. This is working perfectly for my 'Screens' - 'IntroScreen' with some shiny logos, 'TitleScreen' and a 'MenuScreen' stacked on top for the title and menu, 'PlayScreen' for the actual gameplay, etc. Each screen has the a bunch of sprites, and an 'Update' and 'Draw', managed by a 'ScreenManager'. In addition to the above, and as suggested as an answer to my other question here, most screens have a 'GameProcessQueue' class full of 'GameProcess'es which lets me do just about anything (animations, youbetcha!), in any order, in sequence or parallel. Why mention all this? When I talk about managing game state I'm thinking more for complex scenarios within a 'Screen'. 'TitleScreen', 'MenuScreen' and the like are all relatively simple. 'Play Screen' less so. How do people manage the different 'states' within the screen (or whatever you call it) that 'does' gameplay? (for me, the 'PlayScreen') I've thought about the following: Enum of different states in the Screen, 'activeState' enum-type variable, switching on the enum in the Screen Update() loop to determine what Screen Update 'sub'-function is called. I can see this getting hairy pretty fast though as screens get more complex and with the 'PlayScreen' becoming a behemoth mega-class. 'State' class with Update loop - a Screen can have any number of 'States', 1+ of which are 'active'. Screen update loop calls update on all active states. States themselves know which screen they belong to, and may even belong to a 'StateManager' which handles transitioning from one state to the next. Once a state is over it's removed from the ScreenState list. The Screen doesn't need a bunch of GameProcessQueues, each State has its own. Abstract Screen further to be more flexible - I can see the similarities between what I've got (game 'Screens' handled by a ScreenManager) and what I want (states within a screen, and a mechanism to manage them). However at the moment I see 'Screens' as high level and very distinct ('PlayScreen' with baddies != 'MenuScreen' with 4 words and event handlers), where as my proposed 'States' are more intrinsically tied to a specific screen with complex requirements. I think. This is for a turn-based board game, so it's easier to define things as a discrete series of steps (IntroAnimation - P1Turn - P2Turn - P1Turn ... - GameOver - .... Obviously with an open-world RPG things are very different, but any advice in this scenario is appreciated. If I'm just going OOP-crazy please say so. Similarly I'm concious there's a huge amount on this site re: state management. But as my first 'serious' game after a couple of false starts I'd like to get this right, and would rather be harassed and modded down than never ask :)

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• Lighting-Reflectance Models & Licensing Issues

  - by codey

  Generally, or specifically, is there any licensing issue with using any of the well known lighting/reflectance models (i.e. the BRDFs or other distribution or approximation functions): Phong, Blinn–Phong, Cook–Torrance, Blinn-Torrance-Sparrow, Lambert, Minnaert, Oren–Nayar, Ward, Strauss, Ashikhmin-Shirley and common modifications where applicable, such as: Beckmann distribution, Blinn distribution, Schlick's approximation, etc. in your shader code utilised in a commercial product? Or is it a non-issue?

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• Camera closes in on the fixed point

  - by V1ncam

  I've been trying to create a camera that is controlled by the mouse and rotates around a fixed point (read: (0,0,0)), both vertical and horizontal. This is what I've come up with: camera.Eye = Vector3.Transform(camera.Eye, Matrix.CreateRotationY(camRotYFloat)); Vector3 customAxis = new Vector3(-camera.Eye.Z, 0, camera.Eye.X); camera.Eye = Vector3.Transform(camera.Eye, Matrix.CreateFromAxisAngle(customAxis, camRotXFloat * 0.0001f)); This works quit well, except from the fact that when I 'use' the second transformation (go up and down with the mouse) the camera not only goes up and down, it also closes in on the point. It zooms in. How do I prevent this? Thanks in advance.

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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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• Execute code at specific intervals, only once?

  - by Mathias Lykkegaard Lorenzen

  I am having an issue with XNA, where I want to execute some code in my Update method, but only at a given interval, and only once. I would like to avoid booleans to check if I've already called it once, if possible. My code is here: if ((gameTime.TotalGameTime.TotalMilliseconds % 500) == 0) { Caret.Visible = !Caret.Visible; } As you may have guessed, it's for a TextBox control, to animate the caret between invisible and visible states. I just have reason to believe that it is called twice or maybe even 3 times in a single update-call, which is bad, and makes it look unstable and jumpy.

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• kubuntu - what's the best smplayer configuration for best quality in hd movies (mkv)

  - by Frank

  I have ubuntu x64 13.04 with kde 4.11 and smplayer v0.8.6 and the last mplayer version from ppa. I have ATI video card HD6870 MSI with fglrx driver v13.4. My kde settings are: Composition mode: Opengl 3.1 graphic system qt: Raster scaling mode: precise Vsync: auto So what's the best configuration for quality over performace in smplayer according to my system specs? For example what do I have to set for the following options? enable postprocessing by default and postprocessing quality output driver Deinterlacing method software equalizer direct rendering double buffering draw video using slices threads for decoding (MPEG-1/2 and H.264 only loop filter use CoreAVC Thanks

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• Doing powerups in a component-based system

  - by deft_code

  I'm just starting really getting my head around component based design. I don't know what the "right" way to do this is. Here's the scenario. The player can equip a shield. The the shield is drawn as bubble around the player, it has a separate collision shape, and reduces the damage the player receives from area effects. How is such a shield architected in a component based game? Where I get confused is that the shield obviously has three components associated with it. Damage reduction / filtering A sprite A collider. To make it worse different shield variations could have even more behaviors, all of which could be components: boost player maximum health health regen projectile deflection etc Am I overthinking this? Should the shield just be a super component? I really think this is wrong answer. So if you think this is the way to go please explain. Should the shield be its own entity that tracks the location of the player? That might make it hard to implement the damage filtering. It also kinda blurs the lines between attached components and entities. Should the shield be a component that houses other components? I've never seen or heard of anything like this, but maybe it's common and I'm just not deep enough yet. Should the shield just be a set of components that get added to the player? Possibly with an extra component to manage the others, e.g. so they can all be removed as a group. (accidentally leave behind the damage reduction component, now that would be fun). Something else that's obvious to someone with more component experience?

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• Learning to optimize with Assembly

  - by niktehpui

  I am a second year student of Computer Games Technology. I recently finished my first prototype of my "kind" of own pathfinder (that doesn't use A* instead a geometrical approach/pattern recognition, the pathfinder just needs the knowledge about the terrain that is in his view to make decisions, because I wanted an AI that could actually explore, if the terrain is already known, then it will walk the shortest way easily, because the pathfinder has a memory of nodes). Anyway my question is more general: How do I start optimizing algorithms/loops/for_each/etc. using Assembly, although general tips are welcome. I am specifically looking for good books, because it is really hard to find good books on this topic. There are some small articles out there like this one, but still isn't enough knowledge to optimize an algorithm/game... I hope there is a modern good book out there, that I just couldn't find...

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• GetContactList stops reporting collisions on welded bodies

  - by Henrique Jung

  I have some strange problem with my game which uses Box2D as physics engine and I'm out of ideas on what I can do to solve it. My game is a class assignment where I need to build a simple game where the main character moves in a 2D environment while square blocks comes from below him. Each time a collision occurs, that block is attached to the character using a weld joint, when three blocks of the same colors are together, they annihilate themselves(an effect similar to Bejeweled). I'm using a recursive function to iterate through all the attached blocks of a given block to see if there are enough blocks for them to be deleted. I'm using GetContactList function to iterate through the list of contacts to see which blocks are adjacent to each other. The results are quite disappointing, the blocks only get annihilated in few cases. After a lot of debugging, I found the issue, but I still don't know how to solve. My issue is: after some time, GetContactList STOPS returning contacts (return NULL) to blocks that were already attached for some time. I spent some time reading the Box2D manual as well as some tutorials and still didn't find any clue of what is happening. Below there's some simplified version of the code that I wrote. for(int a = 0; a < blocksList.size(); a++) { blocksList[a].BuildConnections(); } And on BuildConnections b2ContactEdge* edge = body->GetContactList(); while(edge != NULL) { if (long_check_to_see_if_there's_a_block_nearby) { // add itself to the list to be anihilated globalList.push_back(this); //if there's, call BuildConnections again on the adjacent block adjacentBody->GetUserData()->BuildConnections; } edge = edge->next; } I know that there's another issue related to circular inclusions, but I fairly sure that this problem isn't causing the problem with the collisions. You can download my entire code from this page if you'd like http://code.google.com/p/fellz/source/list

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• Audio Panning using RtAudio

  - by user1801724

  I use Rtaudio library. I would like to implement an audio program where I can control the panning (e.g. shifting the sound from the left channel to the right channel). In my specific case, I use a duplex mode (you can find an example here: duplex mode). It means that I link the microphone input to the speaker output. I seek on the web, but I did not find anything useful. Should I apply a filter on the output buffer? What kind of filter? Can anyone help me? Thanks

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• Tool for creating complex paths?

  - by TerryB

  I want to create some fairly complex predefined paths for my AI sprites to follow. I'll need to use curves, splines etc to get the effect I want. Is there a drawing tool out there that will allow me to draw such curves, "mesh" them by placing lots of points along them at some defined density and then output the coordinates of all of those points for me? I could write this tool myself but hopefully one of the drawing packages can do this? Cheers!

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• Maximum number of controllers Unity3D can handle

  - by N0xus

  I've been trying to find out the maximum amount of xbox controller Unity3D can handle on one editor. I know through networking, Unity is capable of having as many people as your hardware can handle. But I want to avoid networking as much as possible. Thus, on a single computer, and in a single screen (think Bomberman and Super Smash Brothers) how many xbox controllers can Unity3D support? I have done work in XNA and remember that only being capable of support 4, but for the life of me, I can't find any information that tells me how many Unity can support.

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• What's wrong with this turn to face algorithm?

  - by Chan

  I implement a torpedo object that chases a rotating planet. Specifically, it will turn toward the planet each update. Initially my implement was: void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (to_target * speed); } which works perfectly for torpedo that is a solid sphere. Now my torpedo is actually a model, which has a forward vector, so using this method looks odd because it doesn't actually turn toward but jump toward. So I revised it a bit to get, double get_rotation_angle(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); double cosine_theta = u.dot(v); // domain of arccosine is [-1, 1] if (cosine_theta > 1) { cosine_theta = 1; } if (cosine_theta < -1) { cosine_theta = -1; } return math3d::to_degree(acos(cosine_theta)); } vector3<float> get_rotation_axis(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); // fix linear case if (u == v || u == -v) { v[0] += 0.05; v[1] += 0.0; v[2] += 0.05; v.normalize(); } vector3<float> axis = u.cross(v); return axis.normal(); } void turn_to_face() { vector3<float> to_target = (target - position); vector3<float> axis = get_rotation_axis(get_forward(), to_target); double angle = get_rotation_angle(get_forward(), to_target); double distance = math3d::distance(position, target); gl_matrix_mode(GL_MODELVIEW); gl_push_matrix(); { gl_load_identity(); gl_translate_f(position.get_x(), position.get_y(), position.get_z()); gl_rotate_f(angle, axis.get_x(), axis.get_y(), axis.get_z()); gl_get_float_v(GL_MODELVIEW_MATRIX, OM); } gl_pop_matrix(); move(); } void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (get_forward() * speed); } The logic is simple, I find the rotation axis by cross product, the angle to rotate by dot product, then turn toward the target position each update. Unfortunately, it looks extremely odds since the rotation happens too fast that it always turns back and forth. The forward vector for torpedo is from the ModelView matrix, the third column A: MODELVIEW MATRIX -------------------------------------------------- R U A T -------------------------------------------------- 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 -------------------------------------------------- Any suggestion or idea would be greatly appreciated.

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• Java 2D Rectangle Collision? [on hold]

  - by Andreas Elia

  I am just wanting to know of another (longer OR shorter) way of getting 100% effective collisions on a 2D plat-former. The current collision system that is in place works from coords on the level and does not always work reliably. Thank you in advance for any help/support. The current system draws a rectangle and is checking to see if any two points collide. From testing, the system can sometimes "glitch" and allow the player to collide into walls etc. Player Class http://pastebin.com/2zE8vz8R Main Class http://pastebin.com/A6Utb3ti

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• Constructive criticsm on my linear sampling Gaussian blur

  - by Aequitas

  I've been attempting to implement a gaussian blur utilising linear sampling, I've come across a few articles presented on the web and a question posed here which dealt with the topic. I've now attempted to implement my own Gaussian function and pixel shader drawing reference from these articles. This is how I'm currently calculating my weights and offsets: int support = int(sigma * 3.0) weights.push_back(exp(-(0*0)/(2*sigma*sigma))/(sqrt(2*pi)*sigma)); total += weights.back(); offsets.push_back(0); for (int i = 1; i <= support; i++) { float w1 = exp(-(i*i)/(2*sigma*sigma))/(sqrt(2*pi)*sigma); float w2 = exp(-((i+1)*(i+1))/(2*sigma*sigma))/(sqrt(2*pi)*sigma); weights.push_back(w1 + w2); total += 2.0f * weights[i]; offsets.push_back(w1 / weights[i]); } for (int i = 0; i < support; i++) { weights[i] /= total; } Here is an example of my vertical pixel shader: vec3 acc = texture2D(tex_object, v_tex_coord.st).rgb*weights[0]; vec2 pixel_size = vec2(1.0 / tex_size.x, 1.0 / tex_size.y); for (int i = 1; i < NUM_SAMPLES; i++) { acc += texture2D(tex_object, (v_tex_coord.st+(vec2(0.0, offsets[i])*pixel_size))).rgb*weights[i]; acc += texture2D(tex_object, (v_tex_coord.st-(vec2(0.0, offsets[i])*pixel_size))).rgb*weights[i]; } gl_FragColor = vec4(acc, 1.0); Am I taking the correct route with this? Any criticism or potential tips to improving my method would be much appreciated.

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• Open GL Android frame-by-frame animation tutorial/example code

  - by Trick

  My first question was asked wrong, so I need to ask again :) I found out, that I will have to do an OpenGL animation for my Android game. The closest (known) example is Talking Tom (but I don't know how they did the animations). I have large PNGs which I would like to put into a animation. For example - 30 PNGs 427×240px at 8 FPS. I know some things already about Open GL, but I am used to learn from example code. And it is quicker that way (so I don't need to invent hot water all over again :)). Does anybody has any points to direct me?

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• Illumination and Shading for computer graphics class

  - by Sam I Am

  I am preparing for my test tomorrow and this is one of the practice questions. I solved it partially but I am confused with the rest. Here is the problem: Consider a gray world with no ambient and specular lighting ( only diffuse lighting). The screen coordinates of a triangle P1,P2,P3, are P1=(100,100), P2= (300,150), P3 = (200, 200). The gray values at P!,P2,P3 are 1/2, 3/4, and 1/4 respectively. The light is at infinity and its direction and gray color are (1,1,1) and 1.0 respectively. The coefficients of diffused reflection is 1/2. The normals of P1,P2,P3 are N1= (0,0,1), N2 = (1,0,0), and N3 = (0,1,0) respectively. Consider the coordinates of three points P1,P2,P3 to be 0. Do not normalize the normals. I have computed that the illumination at the 3 vertices P1,P2,P3 is (1/4,3/8,1/8). Also I computed that interpolation coefficients of a point P inside the triangle whose coordinates are (220, 160) are given by (1/5,2/5,2/5). Now I have 4 more questions regarding this problem. 1) The illumination at P using Gouraud Shading is: i) 1/2 The answer is 1/2, but I have no idea how to compute it.. 2) The interpolated normal at P is given by i) (2/5, 2/5,1/5) ii) (1/2, 1/4, 1/4) iii) (3/5, 1/5, 1/5) 3) The interpolated color at P is given by: i) 1/2 Again, I know the correct answer but no idea how to solve it 4) The illumination at P using Phong Shading is i) 1/4 ii) 9/40 iii) 1/2

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• Animating DOM elements vs refreshing a single Canvas

  - by mgibsonbr

  A few years ago, when the HTML Canvas element was still kinda fresh, I wrote a small game in a rather "unusual" way: each game element had its own canvas, and frequently animated elements even had multiple canvases, one for each animation sprite. This way, the translation would be done by manipulating the DOM position of the canvases, while the sprite animation would consist of altering the visibility of the already drawn canvases. (z-indexes, of course, were the tricky part) It worked like a charm: even in IE6 with excanvas it showed a decent performance, and everything was rather consistent between browsers, including some smartphones. Now I'm thinking in writing a larger game engine in the same fashion, so I'm wondering whether it would be a good idea to do so in the current context (with all the advances in browsers and so on). I know I'm trading memory for time, so this needs to be customizable (even at runtime) for each machine the game will be running. But I believe using separate canvases would also help to avoid the game "freezing" on CPU spikes, since the translation would still happen even if the redraws lag for a while. Besides, the browsers' rendering engines are already optimized in may ways, so I'm guessing this scheme would also reduce the load on the CPU (in contrast to doing everything in JavaScript - specially the less optimized ones). It looks good in my head, but I'd like to hear the opinion of more experienced people before proceeding further. Is there any known drawback of doing this? I'm particulartly unexperienced in dealing with the GPU, so I wonder whether this "trick" would nullify any benefit of using a single, big canvas. Or maybe on modern devices it's overkill (though I'm skeptic about the claims that canvas+js - especially WebGL - will ever be a good alternative to native code). Any thoughts?

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• Tessellation Texture Coordinates

  - by Stuart Martin

  Firstly some info - I'm using DirectX 11 , C++ and I'm a fairly good programmer but new to tessellation and not a master graphics programmer. I'm currently implementing a tessellation system for a terrain model, but i have reached a snag. My current system produces a terrain model from a height map complete with multiple texture coordinates, normals, binormals and tangents for rendering. Now when i was using a simple vertex and pixel shader combination everything worked perfectly but since moving to include a hull and domain shader I'm slightly confused and getting strange results. My terrain is a high detail model but the textured results are very large patches of solid colour. My current setup passes the model data into the vertex shader then through the hull into the domain and then finally into the pixel shader for use in rendering. My only thought is that in my hull shader i pass the information into the domain shader per patch and this is producing the large areas of solid colour because each patch has identical information. Lighting and normal data are also slightly off but not as visibly as texturing. Below is a copy of my hull shader that does not work correctly because i think the way that i am passing the data through is incorrect. If anyone can help me out but suggesting an alternative way to get the required data into the pixel shader? or by showing me the correct way to handle the data in the hull shader id be very thankful! cbuffer TessellationBuffer { float tessellationAmount; float3 padding; }; struct HullInputType { float3 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; float3 tangent : TANGENT; float3 binormal : BINORMAL; float2 tex2 : TEXCOORD1; }; struct ConstantOutputType { float edges[3] : SV_TessFactor; float inside : SV_InsideTessFactor; }; struct HullOutputType { float3 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; float3 tangent : TANGENT; float3 binormal : BINORMAL; float2 tex2 : TEXCOORD1; float4 depthPosition : TEXCOORD2; }; ConstantOutputType ColorPatchConstantFunction(InputPatch<HullInputType, 3> inputPatch, uint patchId : SV_PrimitiveID) { ConstantOutputType output; output.edges[0] = tessellationAmount; output.edges[1] = tessellationAmount; output.edges[2] = tessellationAmount; output.inside = tessellationAmount; return output; } [domain("tri")] [partitioning("integer")] [outputtopology("triangle_cw")] [outputcontrolpoints(3)] [patchconstantfunc("ColorPatchConstantFunction")] HullOutputType ColorHullShader(InputPatch<HullInputType, 3> patch, uint pointId : SV_OutputControlPointID, uint patchId : SV_PrimitiveID) { HullOutputType output; output.position = patch[pointId].position; output.tex = patch[pointId].tex; output.tex2 = patch[pointId].tex2; output.normal = patch[pointId].normal; output.tangent = patch[pointId].tangent; output.binormal = patch[pointId].binormal; return output; } Edited to include the domain shader:- [domain("tri")] PixelInputType ColorDomainShader(ConstantOutputType input, float3 uvwCoord : SV_DomainLocation, const OutputPatch<HullOutputType, 3> patch) { float3 vertexPosition; PixelInputType output; // Determine the position of the new vertex. vertexPosition = uvwCoord.x * patch[0].position + uvwCoord.y * patch[1].position + uvwCoord.z * patch[2].position; output.position = mul(float4(vertexPosition, 1.0f), worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix); output.depthPosition = output.position; output.tex = patch[0].tex; output.tex2 = patch[0].tex2; output.normal = patch[0].normal; output.tangent = patch[0].tangent; output.binormal = patch[0].binormal; return output; }

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• Wikipedia A* pathfinding algorithm takes a lot of time

  - by Vee

  I've successfully implemented A* pathfinding in C# but it is very slow, and I don't understand why. I even tried not sorting the openNodes list but it's still the same. The map is 80x80, and there are 10-11 nodes. I took the pseudocode from here Wikipedia And this is my implementation: public static List<PGNode> Pathfind(PGMap mMap, PGNode mStart, PGNode mEnd) { mMap.ClearNodes(); mMap.GetTile(mStart.X, mStart.Y).Value = 0; mMap.GetTile(mEnd.X, mEnd.Y).Value = 0; List<PGNode> openNodes = new List<PGNode>(); List<PGNode> closedNodes = new List<PGNode>(); List<PGNode> solutionNodes = new List<PGNode>(); mStart.G = 0; mStart.H = GetManhattanHeuristic(mStart, mEnd); solutionNodes.Add(mStart); solutionNodes.Add(mEnd); openNodes.Add(mStart); // 1) Add the starting square (or node) to the open list. while (openNodes.Count > 0) // 2) Repeat the following: { openNodes.Sort((p1, p2) => p1.F.CompareTo(p2.F)); PGNode current = openNodes[0]; // a) We refer to this as the current square.) if (current == mEnd) { while (current != null) { solutionNodes.Add(current); current = current.Parent; } return solutionNodes; } openNodes.Remove(current); closedNodes.Add(current); // b) Switch it to the closed list. List<PGNode> neighborNodes = current.GetNeighborNodes(); double cost = 0; bool isCostBetter = false; for (int i = 0; i < neighborNodes.Count; i++) { PGNode neighbor = neighborNodes[i]; cost = current.G + 10; isCostBetter = false; if (neighbor.Passable == false || closedNodes.Contains(neighbor)) continue; // If it is not walkable or if it is on the closed list, ignore it. if (openNodes.Contains(neighbor) == false) { openNodes.Add(neighbor); // If it isn’t on the open list, add it to the open list. isCostBetter = true; } else if (cost < neighbor.G) { isCostBetter = true; } if (isCostBetter) { neighbor.Parent = current; // Make the current square the parent of this square. neighbor.G = cost; neighbor.H = GetManhattanHeuristic(current, neighbor); } } } return null; } Here's the heuristic I'm using: private static double GetManhattanHeuristic(PGNode mStart, PGNode mEnd) { return Math.Abs(mStart.X - mEnd.X) + Math.Abs(mStart.Y - mEnd.Y); } What am I doing wrong? It's an entire day I keep looking at the same code.

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• GPU hung when switching graphic card

  - by Lie Ryan

  I have a laptop (Dell Inspiron N4110) with a switchable graphic. $ lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) 01:00.0 VGA compatible controller: ATI Technologies Inc NI Whistler [AMD Radeon HD 6600M Series] (rev ff) Normally, my laptop starts with both graphic cards enabled, which caused the laptop to turn very hot and the fan to become very noisy. I have been using a small script to disable the Radeon card. For some time, I'm quite happy with this arrangement. However, I have been having some issues with the Intel card (IGD), the Intel card often randomly hang when running OpenGL apps; and so I want to give the Radeon card (DIS) another chance. I have never been able to switch to the Radeon card, but recently, I found out that if I do a "delayed switching" (DDIS): # echo "DDIS" > /sys/kernel/debug/vgaswitcheroo/switch root@lieryan-dell-ubuntu:/sys/kernel/debug/vgaswitcheroo# cat switch 0:IGD:+:Pwr:0000:00:02.0 1:DIS: :Pwr:0000:01:00.0 then I logoff (i.e. to restart X), the screen switch to pseudo-tty and then it stuck there freezing. At this situation, mouse and keyboard stops working so I can't switch to another ptty. I tried ssh-ing from another computer to salvage logs (dmesg at that point) and whatnot; I found out that when freezing, the active graphic card is the AMD card: -- this is from ssh -- # cat switch 0:IGD: :Off:0000:00:02.0 1:DIS:+:Pwr:0000:01:00.0 but the GPU is apparently hung, looking at dmesg gives: ... [ 1411.649974] vga_switcheroo: client 0 refused switch [ 1411.649985] vga_switcheroo: setting delayed switch to client 1 [ 1423.911759] vga_switcheroo: processing delayed switch to 1 [ 1424.006564] fbcon: Remapping primary device, fb1, to tty 1-63 [ 1424.006799] i915: switched off [ 1424.840351] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1425.718088] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1426.622377] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1427.355683] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1428.193549] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id ... the invalid framebuffer id error is repeated for many times over ... I were able to successfully recover by switching back to the Intel card and restarting X from ssh; indicating that only the Radeon card has problems switching. System info: $ uname -a Linux lieryan-dell-ubuntu 3.0.0-14-generic #23-Ubuntu SMP Mon Nov 21 20:28:43 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 11.10 Release: 11.10 Codename: oneiric The laptop also do not have the option to set graphic card at BIOS and the proprietary driver, fglrx, also have never worked; when I installed it through jockey ("Additional Drivers"), glxinfo showed that it still being rendered by Mesa, the /sys/kernel/debug/vgaswitcheroo directory has gone missing, and the driver crashes with a traceback if I use xorg.conf to tell X to use fglrx. Anyone had any idea if it is possible to use this AMD card either with the radeon or the fglrx driver? logs: dmesg

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• Drawing simple geometric figures with DrawUserPrimitives?

  - by Navy Seal

  I'm trying to draw a simple triangle based on an array of vertex. I've been searching for a tutorial and I found a simple example on riemers but I couldn't get it to work. I think it was made for XNA 3 and it seems there were some changes to XNA 4? Using this example: http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series1/The_first_triangle.php I get this error: Additional information: The current vertex declaration does not include all the elements required by the current vertex shader. TextureCoordinate0 is missing. I'm not english so I'm having some trouble to understand everything. For what I understand error is confusing because I'm trying to draw a triangle color based and not texture based and it shouldn't need a texture. Also I saw some articles about dynamic shadows and lights and I would like to know if this is the kind of code used to do it with some tweaks like culling because I'm wondering if its heavy code for performance in real time.

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