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• Whole continent simulation [on hold]

  - by user2309021

  Let's suppose I am planning to create a simulation of an entire continent at some point in the past (let's say, around 0 A.D). Is it feasible to spawn a hundred million actors that interact with each other and their environments? Having them reproduce, extract resources, etc? The fact is that I actually want to create a simulation that allows me to zoom in from a view of the entire continent up to a single village, and interact with it. (Think as if you could keep zooming in the campaign map of any Total War game and the transition to the battle map was seamless, not a change of the "game mode"). By the way, I have never made a game in my entire life (I have programmed normal desktop applications, though), so I am really having trouble wrapping my head around how to implement such a thing. Even while thinking about how to implement a simple population simulator, without a graphical interface, I think that the O(n) complexity of traversing an array and telling all people to get one year older each time the program ticks is kind of stupid. Any kind help would be greatly appreciated :) EDIT: After being put on hold, I shall specify a question. How would you implement a simulation of all basic human dynamics (reproduction, resource consumption) in an entire continent (with millions of people)?

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• Double Buffering in Panda3D (C++)

  - by jsvcycling

  How would I go about using Double Buffering (to create a loading screen) in Panda3D using C++? I've searched Google and found some forums that talk about the concept of swapping buffers, but I haven't seen any that show any type of source code (specifically Panda3D/C++). I'd like to try and stay away from using pure OpenGL code and work it through Panda3D, but if I have no other choice, then I'll have to go with OpenGL coding.

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• How can I get my first-person character in Unity to move to a ledge with an animation?

  - by BallzOfSteel

  I'm trying to get this to happen: The character walks up to a large crate, the player presses a button, and an animation starts playing where the character climbs up on to the crate. (all in first person view). So far I tried this with normal "First Person Controller" Prefab in Unity. My code so far: function OnTriggerStay(other : Collider){ if(other.tag == "GrabZone"){ if(Input.GetKeyDown("e")){ animation.Play("JumpToLedge"); } } } However when i use this on The FPC it will always play from the position the animation is created on. I also tried to create an empty game object, placing the FPC in there. Gives same effect. I also tried just animating the graphics of the FPC alone. This seems to work but since the Character Controller itself is not animated that stays onthe ground. So the whole FPC wont work anymore. Is there anyway i could let this animation play on the local position the player is on at that time? Or can you think of any other logical solution for a grab and climb?

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• android shut-down errors / thread problems

  - by iQue

  Im starting to deal with some stuff in my game that I thought were "minor problems" and one of these are that I get an error every time I shut down my game that looks like this: 09-05 21:40:58.320: E/AndroidRuntime(30401): FATAL EXCEPTION: Thread-4898 09-05 21:40:58.320: E/AndroidRuntime(30401): java.lang.NullPointerException 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainGamePanel.render(MainGamePanel.java:94) 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainThread.run(MainThread.java:101) on these lines is my GameViews rendering-method and the line in my Thread that calls my GameViews rendering-method. Im guessing Something in my surfaceDestroyed(SurfaceHolder holder) is wrong, or maybe Im not ending the tread in the right place. My surfaceDestroyed-method: public void surfaceDestroyed(SurfaceHolder holder) { Log.d(TAG, "Surface is being destroyed"); boolean retry = true; ((MainThread)thread).setRunning(false); while (retry) { try { ((MainThread)thread).join(); retry = false; } catch (InterruptedException e) { } } Log.d(TAG, "Thread was shut down cleanly"); } Also, In my activity for this View my onPaus, onDestoy and onStop are empty, do I maybe need to add something there? The crash occurs when I press my home-button on the phone, or any other button that makes the game stop. But as I understand it the onPaus is called when you press the Home-button.. This is really new territory for me so Im sorry if im missing something obvious or something really big. adding my surfaceCreated method asweel since that is where I start this thread: public void surfaceCreated(SurfaceHolder holder) { controls = new GameControls(this); setOnTouchListener(controls); timer1.schedule(new Task(this), 0, delay1); thread.setRunning(true); thread.start(); } and aslong as this is running, my game is rendering and updating.

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• Html5 games, what is the standard dimension to use?

  - by aoi

  I am trying to make html5 games to be played on the browser(not offline apps), and I am trying to support the maximum number of platforms, hence I need to know what dimension should I use for the game canvas so that it works in the most number of places. Also is there anyway to "scale" a large game to fit in the tiny size of iphone(around 320x356px I think). By "scale" I don't mean to actually resize just the canvas, as because that can mess up the coordinate based calculations, and for a large number of objects, re-positioning based on canvas size can be a real hassle.

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• How can I imitate interaction and movement in Diablo II?

  - by user422318

  I'm prototyping a simple browser-based game. It's played from a top down perspective on a 2d canvas. You left-click on a point on the map, and your character will begin walking to it. If you click on a different point on the map, then your character will begin walking to the new point. It's similar to Diablo II: http://www.youtube.com/watch?v=EvDKt-To6K0&feature=related How can I best imitate this movement system for a player? Ideas... Track current coords and target coords If target coords are exactly up, left, right, or down, then increment appropriate direction until you get there Implied else: target coords are in a quadrant. To make this movement look natural, character will have to move diagonally. For example, pretend the target is to the northeast. For each game frame, alternate incrementing current coordinates in the north and then east directions.

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• Recommended formats to store bitmaps in memory?

  - by Geotarget

  I'm working with general purpose image rendering, and high-performance image processing, and so I need to know how to store bitmaps in-memory. (24bpp/32bpp, compressed/raw, etc) I'm not working with 3D graphics or DirectX / OpenGL rendering and so I don't need to use graphics card compatible bitmap formats. My questions: What is the "usual" or "normal" way to store bitmaps in memory? (in C++ engines/projects?) How to store bitmaps for high-performance algorithms, such that read/write times are the fastest? (fixed array? with/without padding? 24-bpp or 32-bpp?) How to store bitmaps for applications handling a lot of bitmap data, to minimize memory usage? (JPEG? or a faster [de]compression algorithm?) Some possible methods: Use a fixed packed 24-bpp or 32-bpp int[] array and simply access pixels using pointer access, all pixels are allocated in one continuous memory chunk (could be 1-10 MB) Use a form of "sparse" data storage so each line of the bitmap is allocated separately, reusing more memory and requiring smaller contiguous memory segments Store bitmaps in its compressed form (PNG, JPG, GIF, etc) and unpack only when its needed, reducing the amount of memory used. Delete the unpacked data if its not used for 10 secs.

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• Can Google Translate's audio files be used in a game?

  - by ashes999

  For my game, I need text-to-speech. Since it's Android, I decided to settle for MP3s, since the range of words spoken is few. For my prototype, I'm using Google Translate to generate the audio since it has awesome pronounciation across multiple languages. But can I use it in production? What if I sell my game for $1 on the app store? All I can find on SE is that the API may be LGPL, and that the licensing page mentions the API is only available for academic research -- nothing more. My usage is a bit different; I'm actually capturing the audio bits and using those instead. I'm curious to know the license for this; I can't find anything with my Google-fu.

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• Android - Force Close - Null Pointer on Canvas?

  - by user22241

  Please bear with me. I have a very odd problem. Basically, my app so far, has 3 activities (a main splash screen, an 'options/menu' screen and the main app). If I follow the very specific steps oulined below, I get a 'null pointer exception' in the 2nd activity) and the app force closes...... Here are the steps: Start the app (a game based on Surfaceview), tap through to the third activity so the game is running, then hit the home key so the game is paused and put to the background, the activity/app is ended through DDMS in the SDK then restarted on the device (all OK so far), now if I hit the back key on the device twice in quick succession, it happens. All other sequence of events is fine, even to the point of pressing the back key, waiting for the previous activity to show, then hitting back again - all OK. Only when the back key is pressed twice in quick succession following all the above steps does the problem occur. I'm assuming that the canvas isn't ready as it's showing as 'null' when this happens, but I'm not sure why this is happening as surely it's happening when I'm trying to go back to activity 1, but the logcat shows the error in activity 2. if I stop the activity running my 'doDraw' method (which referenced the canvas), then all is OK - so I can safely assume it is the canvas causing the problem. Also, if I skip my first activity (which is a very basic full-screen button which just displays a splashscreen and waits for the user to tap the screen), and make my 2nd activity the launch activity, again, it is OK. this is the part of the code that I think is probably relevant: @Override public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { vheight = this.getHeight(); vwidth = this.getWidth(); } @Override public void surfaceCreated(SurfaceHolder holder) { vheight = this.getHeight(); vwidth = this.getWidth(); this.viewWidth = vwidth; this.viewHeight = vheight; if (runthread==false){ if (preThread.getState()==Thread.State.TERMINATED){ preThread = new OptionsThread(thisholder, thiscontext, thishandler); } preThread.setRunning(true); preThread.start();} } @Override public void surfaceDestroyed(SurfaceHolder holder) { preThread.setRunning(false); //Stop the loop boolean retry = true; //Stop the thread while (retry) { try { preThread.join(); retry = false; } catch (InterruptedException e) { } } Thank you all for any help you can offer

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• Yet another frustum culling question

  - by Christian Frantz

  This one is kinda specific. If I'm to implement frustum culling in my game, that means each one of my cubes would need a bounding sphere. My first question is can I make the sphere so close to the edge of the cube that its still easily clickable for destroying and building? Frustum culling is easily done in XNA as I've recently learned, I just need to figure out where to place the code for the culling. I'm guessing in my method that draws all my cubes but I could be wrong. My camera class currently implements a bounding frustum which is in the update method like so frustum.Matrix = (view * proj); Simple enough, as I can call that when I have a camera object in my class. This works for now, as I only have a camera in my main game class. The problem comes when I decide to move my camera to my player class, but I can worry about that later. ContainmentType CurrentContainmentType = ContainmentType.Disjoint; CurrentContainmentType = CamerasFrustrum.Contains(cubes.CollisionSphere); Can it really be as easy as adding those two lines to my foreach loop in my draw method? Or am I missing something bigger here? UPDATE: I have added the lines to my draw methods and it works great!! So great infact that just moving a little bit removes the whole map. Many factors could of caused this, so I'll try to break it down. cubeBoundingSphere = new BoundingSphere(cubePosition, 0.5f); This is in my cube constructor. cubePosition is stored in an array, The vertices that define my cube are factors of 1 ie: (1,0,1) so the radius should be .5. I least I think it should. The spheres are created every time a cube is created of course. ContainmentType CurrentContainmentType = ContainmentType.Disjoint; foreach (Cube block in cube.cubes) { CurrentContainmentType = cam.frustum.Contains(cube.cubeBoundingSphere); ///more code here if (CurrentContainmentType != ContainmentType.Disjoint) { cube.Draw(effect); } Within my draw method. Now I know this works because the map disappears, its just working wrong. Any idea on what I'm doing wrong?

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• Problems loading Hilva tutorials

  - by Beska

  I'm a newcomer to XNA, and I'm evaluating some libraries. The Hilva Graphics Engine looks interesting, and I'm trying to run their tutorials. However, all of them give me errors. For example, if I download the ParallaxMappingSample demo, and try to build it, I get Error 1 Error loading pipeline assembly "C:\Users\Me\Desktop\ParallaxMappingSample\Hilva.Content.dll". ParallaxMappingSample I get similar errors for all of the samples. Unfortunately, this error isn't very enlightening. I can see the Hilva.Content.dll in the appropriate directory. I tried removing and readding the reference from the content project, but I get the same error. I'm not sure it's relevant, but I'm on Windows 7, I'm using Microsoft Visual Studio 2010, and XNA 4.0. Is there an easy (or difficult) solution? EDIT: If you happen to try this, even if you don't have a solution, let me know about it in a comment. Whether it works for you, or if you get the same problem...either result would be something that might let me know if it's just a problem with the tutorial, or if it's on my end.

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• Point in Polygon, Ray Method: ending infinite line

  - by user2878528

  Having a bit of trouble with point in polygon collision detection using the ray method i.e. http://en.wikipedia.org/wiki/Point_in_polygon My problem is I need to give an end to the infinite line created. As with this infinite line I always get an even number of intersections and hence an invalid result. i.e. ignore or intersection to the right of the point being checked what I have what I want My current code based of Mecki awesome response for (int side = 0; side < vertices.Length; side++) { // Test if current side intersects with ray. // create infinite line // See: http://en.wikipedia.org/wiki/Linear_equation a = end_point.Y - start_point.Y; b = start_point.X - end_point.X; c = end_point.X * start_point.Y - start_point.X * end_point.Y; //insert points of vector d2 = a * vertices[side].Position.X + b * vertices[side].Position.Y + c; if (side - 1 < 0) d1 = a * vertices[vertices.Length - 1].Position.X + b * vertices[vertices.Length - 1].Position.Y + c; else d1 = a * vertices[side-1].Position.X + b * vertices[side-1].Position.Y + c; // If points have opposite sides, intersections++; if (d1 > 0 && d2 < 0 ) intersections++; if (d1 < 0 && d2 > 0 ) intersections++; } //if intersections odd inside = true if ((intersections % 2) == 1) inside = true; else inside = false;

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• Any advice for dynamic music control?

  - by Assembler

  I would like to be able to dynamically progress the score, and affect the volume levels of separate channels within the music. How could I do this? From my experience with mod music (olden days Amiga music, Mod Tracker, Scream Tracker, Fast Tracker II, Impulse Tracker etc etc), I believe this is the best way to tackle the problem, to allow the music to move from one loop to another, without anything mixed down. I want to do this in AS3, and am considering pulling apart Flod to make this happen

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• How to prevent "underwater sight" in games

  - by CPP_Person

  In many games where the player can go underwater, it seems like when you look where the top half of the screen is in the air, and the bottom half the screen is in the water, it's almost like the water doesn't exist and the player is... flying slowly with water sounds? Is there a logical way to solve this? An algorithm? Doesn't seem like any solution has come up yet since many games still have this. I don't want to make the same mistake.

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• How do I make a simple level system?

  - by ROROX

  I've been learning programming for a while and things are slow but steady. I only have a couple experiments that look something like a game (JavaScript,HTML5,CANVAS). One of the things I would like to establish this early in my process though is a basic level system to my games. I'm thinking like Atari, NES type simple. mainMenu , level1 , level2 , ... Later I'll work on including such screens as; titleScreen , pause , highScore. But for now just looking for the basics. Any good articles/tutorial links would help. Or just a snippet of code I can look over. Thank you kindly :)

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• Wall avoidance steering

  - by Vodemki

  I making a small steering simulator using the reynolds boid algorythm. Now I want to add a wall avoidance feature. My walls are in 3D and defined using two points like that: ---------. P2 | | P1 .--------- My agents have a velocity, a position, etc... Could you tell me how to make avoidance with my agents ? Vector2D ReynoldsSteeringModel::repulsionFromWalls() { Vector2D force; vector<Wall *> wallsList = walls(); Point2D pos = self()->position(); Vector2D velocity = self()->velocity(); for (unsigned i=0; i<wallsList.size(); i++) { //TODO } return force; } Then I use all the forces returned by my boid functions and I apply it to my agent. I just need to know how to do that with my walls ? Thanks for your help.

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• Scene transitions

  - by Mars

  It's my first time working with actual scenes/states, aka DrawableGameComponents, which work separate from one another. I'm now wondering what's the best way to make transitions between them, and how to affect them from other scenes. Lets say I wanted to "push" one screen to the right, with another one coming in at the same time. Naturally I'd have to keep drawing both, until the transition is complete. And I'd have to adjust the coordinates I'm drawing at while doing it. Is there a way around specifically handling this special case in every single scene? Or of I wanted to fade one into the other. Basically the question stays the same, how would you do that without having to handle it in every single scene? While writing this I'm realizing it will be the same thing for all kinds of transitions. Maybe a central Draw method in the manager could be a solution, where parameters and effects are applied when necessary. But this wouldn't work if objects that are drawn have their own method, and aren't drawn within the scene, or if an effect has to be applied to the whole scene. That means, maybe scenes have to be drawn to their own rendertarget? That way one call to the base class after the normal drawing could be enough, to apply the effects, while drawing it to the main render target. But I once heard there are problems when switching from target to target, back and forth. So is that even a viable option? As you can see, I have some basic ideas how it might work... but nothing specific. I'd like to learn what's the common way to achieve such things, a general way to apply all kinds of transitions.

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• What library should I use for 2D Geometry? [closed]

  - by Luka

  I've been working on a 2D game in java, but found that java just didn't cut it for me and had forced me to a lot of bad design choices, so I've decided to port all my work to c++. The main reason I've decided change to c++ is that i had reached a point where i had 3 geometry libraries (the native, one from the game engine and one to handle "complex" polygons), none of witch worked very well together and i couldn't keep track of them. I'm new to c++, but i know all the basics. My question is, what would be a good geometry library to use, ideally it should be able to handle integer and decimal data types, have point, line, and polygon classes witch are able to check for intersection and contains. Thanks in advance, Luka

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• Collision Systems Implementation

  - by hrr4

  Just curious what might be a good way to implement a decent collision system. As a class inherited by a base Entity class? Currently I'm stuck and could just use a couple better ideas than my own. Any help is appreciated! Edit: Sorry, it's 2D Collisioning but honestly, I'm not looking for specific collision methods. I'm looking more about the lines of implementation. Just curious of some of the common methods of how to implement collision systems such as: Should the entire collision system be it's own class? What, if anything, should be inheritable? These are some of my questions. Sorry for the confusion.

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• How do I create weapon attachments?

  - by Tron86

  My question is; I am developing a game for XNA and I am trying to create a weapon attachment for my player model. My player model loads the .md3 format and reads tags for attachment points. I am able to get the tag of my model's hand. And I am also able to get the tag of my weapon's handle. Each tag I am able to get the rotation and position of and this is how I am calculating it: Model.worldMatrix = Matrix.CreateScale(Model.scale) * Matrix.CreateRotationX(-MathHelper.PiOver2) * Matrix.CreateRotationY(MathHelper.PiOver2); Pretty simple, the player model has a scale and its orientation(it loads on its side so I just use a 90 degree X axis rotation, and a Y axis rotation to face away from the camera). I then calculate the torso tag on the lower body, which gives me a local coordinate at the waist. Then I take that matrix and calculate the tag_weapon in the upper body. This gives me the hand position in local space. I also get the rotation matrix from that tag that I store for later use. All this seems to work fine. Now I move onto my weapon: Matrix weaponWorld = Matrix.CreateScale(CurrentWeapon.scale) * Matrix.CreateRotationX(-MathHelper.PiOver2) * TagRotationMatrix * Matrix.CreateTranslation(HandTag.Position) * Matrix.CreateRotationY(PlayerRotation) * Matrix.CreateTranslation(CollisionBody.Position) * You may notice the weapon matrix gets rotated by 90 degress on the X axis as well. This is because they load in on their sides. Once again this seems pretty simple and follows the SRT order I keep reading about. My TagRotation matrix is the hand's rotation. HandTag.Position is its position in local space. CreateRotationY(PlayerRotation) is the player's rotation in world space, and the CollisionBody.Position is the player's world location. Everything seems to be in order, and almost works in game. However when the gun spawns and follows the player's hand it seems to be flipped on an axis every couple frames. Almost like the X or Y axis is being inversed then put right back. Its hard to explain and I am totally stumped. Even removing all my X axis fixes does nothing to solve the problem. Hopefully I explained everything enough as I am a bit new to this! Thanks!

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• How can I render a semi transparent model with OpenGL correctly?

  - by phobitor

  I'm using OpenGL ES 2 and I want to render a simple model with some level of transparency. I'm just starting out with shaders, and I wrote a simple diffuse shader for the model without any issues but I don't know how to add transparency to it. I tried to set my fragment shader's output (gl_FragColor) to a non opaque alpha value but the results weren't too great. It sort of works, but it looks like certain model triangles are only rendered based on the camera position... It's really hard to describe what's wrong so please watch this short video I recorded: http://www.youtube.com/watch?v=s0JqA0rZabE I thought this was a depth testing issue so I tried playing around with enabling/disabling depth testing and back face culling. Enabling back face culling changes the output slightly but the problem in the video is still there. Enabling/disabling depth testing doesn't seem to do anything. Could anyone explain what I'm seeing and how I can add some simple transparency to my model with the shader? I'm not looking for advanced order independent transparency implementations. edit: Vertex Shader: // color varying for fragment shader varying mediump vec3 LightIntensity; varying highp vec3 VertexInModelSpace; void main() { // vec4 LightPosition = vec4(0.0, 0.0, 0.0, 1.0); vec3 LightColor = vec3(1.0, 1.0, 1.0); vec3 DiffuseColor = vec3(1.0, 0.25, 0.0); // find the vector from the given vertex to the light source vec4 vertexInWorldSpace = gl_ModelViewMatrix * vec4(gl_Vertex); vec3 normalInWorldSpace = normalize(gl_NormalMatrix * gl_Normal); vec3 lightDirn = normalize(vec3(LightPosition-vertexInWorldSpace)); // save vertexInWorldSpace VertexInModelSpace = vec3(gl_Vertex); // calculate light intensity LightIntensity = LightColor * DiffuseColor * max(dot(lightDirn,normalInWorldSpace),0.0); // calculate projected vertex position gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; } Fragment Shader: // varying to define color varying vec3 LightIntensity; varying vec3 VertexInModelSpace; void main() { gl_FragColor = vec4(LightIntensity,0.5); }

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• How are vertex shader outs sent as inputs to the fragment shader?

  - by Jeffrey

  I'm learning some OpenGL 3.2 way of doing things and I think it's quite great, I'm actually understanding more of shaders and non-fixed pipeline in 1 week rather than those 2 years I tried to learn OpenGL fixed pipeline functions. But here's my question: From what I think I've understood the vertex shader is run for each vertexes in the VBO. But the fragments shader is run per each pixel (is that right?) which is a huge number compared to let's say 3 vertexes of a triangle. Now it seems that in the vertex shader the out variables (like colors and stuff) are passed 1 to 1 to the fragment shader. But let's say that I pass to the fragment shader the position of the vertex in the vertex shader. How is all executed? What vertex (A, B or C of the hipothetical triangle) is passed per each fragment and why?

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• Material System

  - by Towelie

  I'm designing Material/Shader System (target API DX10+ and may be OpenGL3+, now only DX10). I know, there was a lot of topics about this, but i can't find what i need. I don't want to do some kind of compilation/parsing scripts in real-time. So there some artist-created material, written at some analog of CG. After it compiled to hlsl code and after to final shader. Also there are some hard-coded ConstantBuffers, like cbuffer EveryFrameChanging { float4x4 matView; float time; float delta; } And shader use shared constant buffers to get parameters. For each mesh in the scene, getting needs and what it can give (normals, binormals etc.) and finding corresponding permutation of shader or calculating missing parts. Also, during build calculating render states and the permutations or hash for this shader which later will be used for sorting or even giving the ID from 0 to ShaderCount w/o gaps to it for sorting. FinalShader have only 1 technique and one pass. After it for each Mesh setting some shader and it's good to render. some pseudo code SetConstantBuffer(ConstantBuffer::PerFrame); foreach (shader in FinalShaders) SetConstantBuffer(ConstantBuffer::PerShader, shader); SetRenderState(shader); foreach (mesh in shader.GetAllMeshes) SetConstantBuffer(ConstantBuffer::PerMesh, mesh); SetBuffers(mesh); Draw(); class FinalShader { public: UUID m_ID; RenderState m_RenderState; CBufferBindings m_BufferBindings; } But i have no idea how to create this CG language and do i really need it?

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• Do I need the 'w' component in my Vector class?

  - by bobobobo

  Assume you're writing matrix code that handles rotation, translation etc for 3d space. Now the transformation matrices have to be 4x4 to fit the translation component in. However, you don't actually need to store a w component in the vector do you? Even in perspective division, you can simply compute and store w outside of the vector, and perspective divide before returning from the method. For example: // post multiply vec2=matrix*vector Vector operator*( const Matrix & a, const Vector& v ) { Vector r ; // do matrix mult r.x = a._11*v.x + a._12*v.y ... real w = a._41*v.x + a._42*v.y ... // perspective divide r /= w ; return r ; } Is there a point in storing w in the Vector class?

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• In 3D camera math, calculate what Z depth is pixel unity for a given FOV

  - by badweasel

  I am working in iOS and OpenGL ES 2.0. Through trial and error I've figured out a frustum to where at a specific z depth pixels drawn are 1 to 1 with my source textures. So 1 pixel in my texture is 1 pixel on the screen. For 2d games this is good. Of course it means that I also factor in things like the size of the quad and the size of the texture. For example if my sprite is a quad 32x32 pixels. The quad size is 3.2 units wide and tall. And the texcoords are 32 / the size of the texture wide and tall. Then the frustum is: matrixFrustum(-(float)backingWidth/frustumScale,(float)backingWidth/frustumScale, -(float)backingHeight/frustumScale, (float)backingHeight/frustumScale, 40, 1000, mProjection); Where frustumScale is 800 for a retina screen. Then at a distance of 800 from camera the sprite is pixel for pixel the same as photoshop. For 3d games sometimes I still want to be able to do this. But depending on the scene I sometimes need the FOV to be different things. I'm looking for a way to figure out what Z depth will achieve this same pixel unity for a given FOV. For this my mProjection is set using: matrixPerspective(cameraFOV, near, far, (float)backingWidth / (float)backingHeight, mProjection); With testing I found that at an FOV of 45.0 a Z of 38.5 is very close to pixel unity. And at an FOV of 30.0 a Z of 59.5 is about right. But how can I calculate a value that is spot on? Here's my matrixPerspecitve code: void matrixPerspective(float angle, float near, float far, float aspect, mat4 m) { //float size = near * tanf(angle / 360.0 * M_PI); float size = near * tanf(degreesToRadians(angle) / 2.0); float left = -size, right = size, bottom = -size / aspect, top = size / aspect; // Unused values in perspective formula. m[1] = m[2] = m[3] = m[4] = 0; m[6] = m[7] = m[12] = m[13] = m[15] = 0; // Perspective formula. m[0] = 2 * near / (right - left); m[5] = 2 * near / (top - bottom); m[8] = (right + left) / (right - left); m[9] = (top + bottom) / (top - bottom); m[10] = -(far + near) / (far - near); m[11] = -1; m[14] = -(2 * far * near) / (far - near); } And my mView is set using: lookAtMatrix(cameraPos, camLookAt, camUpVector, mView); * UPDATE * I'm going to leave this here in case anyone has a different solution, can explain how they do it, or why this works. This is what I figured out. In my system I use a 10th scale unit to pixels on non-retina displays and a 20th scale on retina displays. The iPhone is 640 pixels wide on retina and 320 pixels wide on non-retina (obsolete). So if I want something to be the full screen width I divide by 20 to get the OpenGL unit width. Then divide that by 2 to get the left and right unit position. Something 32 units wide centered on the screen goes from -16 to +16. Believe it or not I have an excel spreadsheet do all this math for me and output all the vertex data for my sprite sheet. It's an arbitrary thing I made up to do .1 units = 1 non-retina pixel or 2 retina pixels. I could have made it .01 units = 2 pixels and someday I might switch to that. But for now it's the other. So the width of the screen in units is 32.0, and that means the left most pixel is at -16.0 and the right most is at 16.0. After messing a bit I figured out that if I take the [0] value of an identity modelViewProjection matrix and multiply it by 16 I get the depth required to get 1:1 pixels. I don't know why. I don't know if the 16 is related to the screen size or just a lucky guess. But I did a test where I placed a sprite at that calculated depth and varied the FOV through all the valid values and the object stays steady on screen with 1:1 pixels. So now I'm just calculating the unityDepth that way. If someone gives me a better answer I'll checkmark it.

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