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  • Strange mesh import problem with Assimp and OpenGL

    - by Morgan
    Using the assimp library for importing 3D data into an OpenGL application. I get some strange problems regarding indexing of the vertices: If I use the following code for importing vertex indices: for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } I get the following result: Instead, if I use the following code: for(int k = 0; k < 2 ; k++) { for (unsigned int t = 0; t < mesh->mNumFaces; ++t) { const struct aiFace * face = &mesh->mFaces[t]; if (face->mNumIndices == 3) { indices->push_back(face->mIndices[0]); indices->push_back(face->mIndices[1]); indices->push_back(face->mIndices[2]); } } } I get the correct result: Hence adding the indices twice, renders the correct result? The OpenGL buffer is populated, like so: glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices->size() * sizeof(unsigned int), indices->data(), GL_STATIC_DRAW); And rendered as follows: glDrawElements(GL_TRIANGLES, vertexCount*3, GL_UNSIGNED_INT, indices->data());

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  • Move a sphere along the swipe?

    - by gameOne
    I am trying to get a sphere curl based on the swipe. I know this has been asked many times, but still it's yearning to be answered. I have managed to add force on the direction of the swipe and it works near perfect. I also have all the swipe positions stored in a list. Now I would like to know how can the curl be achieved. I believe the the curve in the swipe can be calculated by the Vector dot product If theta is 0, then there is no need to add the swipe. If it is not, then add the curl. Maybe this condition is redundant if I managed to find how to curl the sphere along the swipe position The code that adds the force to sphere based on the swipe direction is as below: using UnityEngine; using System.Collections; using System.Collections.Generic; public class SwipeControl : MonoBehaviour { //First establish some variables private Vector3 fp; //First finger position private Vector3 lp; //Last finger position private Vector3 ip; //some intermediate finger position private float dragDistance; //Distance needed for a swipe to register public float power; private Vector3 footballPos; private bool canShoot = true; private float factor = 40f; private List<Vector3> touchPositions = new List<Vector3>(); void Start(){ dragDistance = Screen.height*20/100; Physics.gravity = new Vector3(0, -20, 0); footballPos = transform.position; } // Update is called once per frame void Update() { //Examine the touch inputs foreach (Touch touch in Input.touches) { /*if (touch.phase == TouchPhase.Began) { fp = touch.position; lp = touch.position; }*/ if (touch.phase == TouchPhase.Moved) { touchPositions.Add(touch.position); } if (touch.phase == TouchPhase.Ended) { fp = touchPositions[0]; lp = touchPositions[touchPositions.Count-1]; ip = touchPositions[touchPositions.Count/2]; //First check if it's actually a drag if (Mathf.Abs(lp.x - fp.x) > dragDistance || Mathf.Abs(lp.y - fp.y) > dragDistance) { //It's a drag //Now check what direction the drag was //First check which axis if (Mathf.Abs(lp.x - fp.x) > Mathf.Abs(lp.y - fp.y)) { //If the horizontal movement is greater than the vertical movement... if ((lp.x>fp.x) && canShoot) //If the movement was to the right) { //Right move float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,10,16))*power); Debug.Log("right "+(lp.x-fp.x));//MOVE RIGHT CODE HERE canShoot = false; //rigidbody.AddForce((new Vector3((lp.x-fp.x)/30,10,16))*power); StartCoroutine(ReturnBall()); } else { //Left move float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,10,16))*power); Debug.Log("left "+(lp.x-fp.x));//MOVE LEFT CODE HERE canShoot = false; //rigidbody.AddForce(new Vector3((lp.x-fp.x)/30,10,16)*power); StartCoroutine(ReturnBall()); } } else { //the vertical movement is greater than the horizontal movement if (lp.y>fp.y) //If the movement was up { //Up move float y = (lp.y-fp.y)/Screen.height*factor; float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,y,16))*power); Debug.Log("up "+(lp.x-fp.x));//MOVE UP CODE HERE canShoot = false; //rigidbody.AddForce(new Vector3((lp.x-fp.x)/30,10,16)*power); StartCoroutine(ReturnBall()); } else { //Down move Debug.Log("down "+lp+" "+fp);//MOVE DOWN CODE HERE } } } else { //It's a tap Debug.Log("none");//TAP CODE HERE } } } } IEnumerator ReturnBall() { yield return new WaitForSeconds(5.0f); rigidbody.velocity = Vector3.zero; rigidbody.angularVelocity = Vector3.zero; transform.position = footballPos; canShoot =true; isKicked = false; } }

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  • How to use UILongPressGestureRecognizer with sprite drag & wait?

    - by ganesh
    May be it's asked before also but I couldn't find any good answer. Please tell me how this can be implemented with UILongPressGestureRecognizer? A user drags a sprite from X location to Y location. Then it waits at Y location (touch is not ended yet) for 1 or 2 secs and release the touch i.e touch is ended. In this case, shouldn't following states be triggered in below order for UILongPressGestureRecognizer: UIGestureRecognizerStateBegan UIGestureRecognizerStateChanged UIGestureRecognizerStateEnded ? My problem is if UIPanGestureRecognizer is also implemented to handle drags, UILongPressGesture is never triggered even after Long waits. Any thoughts?

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  • How to determine character's foot contact point on a uniform triangle mesh terrain?

    - by xenon
    For a terrain that is modelled by a heightmap with a uniform triangle mesh, what are some techniques I could use to determine the contact point of the foot of a character standing on the terrain? Since the terrain's Y values are altered by the heightmap, they won't be flat any more. As the character moves on the terrain, it has to know at which values of Y-value its foot should be. Conceptually, what are some methods and techniques to determine the contact point of the character's foot standing on the terrain?

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  • Restrict Tile Map to its boundaries

    - by Farooq Arshed
    I have loaded a tmx file in cocos2dx and now I am trying to implement panning. I have successfully implemented the panning first part where the map moves. Now I want to restrict the map so it does not display the map beyond its boundary where it shows black screen. I am confused as to how to implement it. Below is my code any help would be appreciated. bool HelloWorld::init() { if ( !CCLayer::init() ) { return false; } const char* tmx= "isometric_grass_and_water.tmx"; _tileMap = new CCTMXTiledMap(); _tileMap->initWithTMXFile(tmx); this->addChild(_tileMap); this->setTouchEnabled(true); return true; } void HelloWorld::ccTouchesBegan(CCSet *touches, CCEvent *event){ CCSetIterator it; for (it=touches->begin(); it!=touches->end(); ++it){ CCTouch* touch = (CCTouch*)it.operator*(); CCLog("touches id: %d", touch->getID()); oldLoc = touch->getLocationInView(); oldLoc = CCDirector::sharedDirector()->convertToGL(oldLoc); } } void HelloWorld::ccTouchesMoved(CCSet *touches, CCEvent *event) { if (touches->count() == 1) { CCTouch* touch = (CCTouch*)( touches->anyObject() ); this->moveScreen(touch); } else if (touches->count() == 2) { this->scaleScreen(touches); } } void HelloWorld::moveScreen(CCTouch* touch) { CCPoint currentLoc = touch->getLocationInView(); currentLoc = CCDirector::sharedDirector()->convertToGL(currentLoc); CCPoint moveTo = ccpSub(oldLoc, currentLoc); moveTo = ccpMult(moveTo, -1); oldLoc = currentLoc; this->setPosition(ccpAdd(this->getPosition(), ccp(moveTo.x, moveTo.y))); }

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  • accessing c++ class members with luaplus

    - by cppanda
    i've implemented LuaPlus in my engine eventmanager successfully and really like the flexibility i gained. but i'm still not exactly where i want to by, because i can't link my c++ classes to a lua class. for example i have a Actor class in c++, and i want to be able to create the same class in lua and gain access to members with luaplus, but i can't figure how i can achieve that. Is this actually luaplus built in functionality, or do i have to write my own interface that exchanges data tables between c++ and lua? my current approach would be to fire an event in luascript that creates an new actor class in c++ code, and transfer its id and the data i need to back to lua. when i modify the data i send the modifications back to c++ code again, but i actually thought there's something in luaplus that exposes this functionality already.

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  • Basic tutorial/introduction for 3d matrices, idealy in c++, without openGl or directX

    - by René Nyffenegger
    I am wondering if there is a simple tutorial that covers the basics of how to initialize rotation, translation and projection matrices, and how to multiply them, and how to get the screen coordinates afterwards for a 3d point. Idealy, the tutorial comes with compilable code and is not dependent on any 3rd party library. Searching the internet, I found lots of tutorials, so this is not the problem. Yet, it seemed all of these either covered openGl or directX, or they were theoretical in nature.

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  • Demystifying "chunked level of detail"

    - by Caius Eugene
    Just recently trying to make sense of implementing a chunked level of detail system in Unity. I'm going to be generating four mesh planes, each with a height map but I guess that isn't too important at the moment. I have a lot of questions after reading up about this technique, I hope this isn't too much to ask all in one go, but I would be extremely grateful for someone to help me make sense of this technique. 1 : I can't understand at which point down the Chunked LOD pipeline that the mesh gets split into chunks. Is this during the initial mesh generation, or is there a separate algorithm which does this. 2 : I understand that a Quadtree data structure is used to store the Chunked LOD data, I think i'm missing the point a bit, but Is the quadtree storing vertex and triangles data for each subdivision level? 3a : How is the camera distance usually calculated. When reading up about quadtree's, Axis-aligned bounding box's are mentioned a lot. In this case would each chunk have a collision bounding box to detect the camera or player is nearby? or is there a better way of doing this? (raycast maybe?) 3b : Do the chunks calculate the camera distance themselves? 4 : Does each chunk have the same "resolution". for example at top level the mesh will be 32x32, will each subdivided node also be 32x32. Example below:

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  • AI control for a ship with physics model

    - by Petteri Hietavirta
    I am looking for ideas how to implement following in 2D space. Unfortunately I don't know much about AI/path finding/autonomous control yet. Let's say this ship can move freely but it has mass and momentum. Also, external forces might affect it (explosions etc). The player can set a target for the ship at any time and it should reach that spot and stop. Without physics this would be simple, just point to the direction and go. But how to deal with existing momentum and then stopping on the spot? I don't want to modify ship's placement directly. edit: Just to make clear, the physics related math of the ship itself is not the problem.

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  • Cool examples of procedural pixel shader effects?

    - by Robert Fraser
    What are some good examples of procedural/screen-space pixel shader effects? No code necessary; just looking for inspiration. In particular, I'm looking for effects that are not dependent on geometry or the rest of the scene (would look okay rendered alone on a quad) and are not image processing (don't require a "base image", though they can incorporate textures). Multi-pass or single-pass is fine. Screenshots or videos would be ideal, but ideas work too. Here are a few examples of what I'm looking for (all from the RenderMonkey samples): PS - I'm aware of this question; I'm not asking for a source of actual shader implementations but instead for some inspirational ideas -- and the ones at the NVIDIA Shader Library mostly require a scene or are image processing effects. EDIT: this is an open-ended question and I wish there was a good way to split the bounty. I'll award the rep to the best answer on the last day.

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  • python Velocity control of the player, why doesn't this work?

    - by Dominic Grenier
    I have the following code inside a while True loop: if abs(playerx) < MAXSPEED: if moveLeft: playerx -= 1 if moveRight: playerx += 1 if abs(playery) < MAXSPEED: if moveDown: playery += 1 if moveUp: playery -= 1 if moveLeft == False and abs(playerx) > 0: playerx += 1 if moveRight == False and abs(playerx) > 0: playerx -= 1 if moveUp == False and abs(playery) > 0: playery += 1 if moveDown == False and abs(playery) > 0: playery -= 1 player.x += playerx player.y += playery if player.left < 0 or player.right > 1000: player.x -= playerx if player.top < 0 or player.bottom > 600: player.y -= playery The intended result is that while an arrow key is pressed, playerx or y increments by one at every loop until it reaches MAXSPEED and stays at MAXSPEED. And that when the player stops pressing that arrow key, his speed decreases. Until it reaches 0. To me, this code explicitly says that... But what actually happens is that playerx or y keeps incrementing regardless of MAXSPEED and continues moving even after the player stops pressing the arrow key. I keep rereading but I'm completely baffled by this weird behavior. Any insights? Thanks.

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  • My grid based collision detection is slow

    - by Fibericon
    Something about my implementation of a basic 2x4 grid for collision detection is slow - so slow in fact, that it's actually faster to simply check every bullet from every enemy to see if the BoundingSphere intersects with that of my ship. It becomes noticeably slow when I have approximately 1000 bullets on the screen (36 enemies shooting 3 bullets every .5 seconds). By commenting it out bit by bit, I've determined that the code used to add them to the grid is what's slowest. Here's how I add them to the grid: for (int i = 0; i < enemy[x].gun.NumBullets; i++) { if (enemy[x].gun.bulletList[i].isActive) { enemy[x].gun.bulletList[i].Update(timeDelta); int bulletPosition = 0; if (enemy[x].gun.bulletList[i].position.Y < 0) { bulletPosition = (int)Math.Floor((enemy[x].gun.bulletList[i].position.X + 900) / 450); } else { bulletPosition = (int)Math.Floor((enemy[x].gun.bulletList[i].position.X + 900) / 450) + 4; } GridItem bulletItem = new GridItem(); bulletItem.index = i; bulletItem.type = 5; bulletItem.parentIndex = x; if (bulletPosition > -1 && bulletPosition < 8) { if (!grid[bulletPosition].Contains(bulletItem)) { for (int j = 0; j < grid.Length; j++) { grid[j].Remove(bulletItem); } grid[bulletPosition].Add(bulletItem); } } } } And here's how I check if it collides with the ship: if (ship.isActive && !ship.invincible) { BoundingSphere shipSphere = new BoundingSphere( ship.Position, ship.Model.Meshes[0].BoundingSphere.Radius * 9.0f); for (int i = 0; i < grid.Length; i++) { if (grid[i].Contains(shipItem)) { for (int j = 0; j < grid[i].Count; j++) { //Other collision types omitted else if (grid[i][j].type == 5) { if (enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].isActive) { BoundingSphere bulletSphere = new BoundingSphere(enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].position, enemy[grid[i][j].parentIndex].gun.bulletModel.Meshes[0].BoundingSphere.Radius); if (shipSphere.Intersects(bulletSphere)) { ship.health -= enemy[grid[i][j].parentIndex].gun.damage; enemy[grid[i][j].parentIndex].gun.bulletList[grid[i][j].index].isActive = false; grid[i].RemoveAt(j); break; //no need to check other bullets } } else { grid[i].RemoveAt(j); } } What am I doing wrong here? I thought a grid implementation would be faster than checking each one.

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  • HLSL Pixel Shader that does palette swap

    - by derrace
    I have implemented a simple pixel shader which can replace a particular colour in a sprite with another colour. It looks something like this: sampler input : register(s0); float4 PixelShaderFunction(float2 coords: TEXCOORD0) : COLOR0 { float4 colour = tex2D(input, coords); if(colour.r == sourceColours[0].r && colour.g == sourceColours[0].g && colour.b == sourceColours[0].b) return targetColours[0]; return colour; } What I would like to do is have the function take in 2 textures, a default table, and a lookup table (both same dimensions). Grab the current pixel, and find the location XY (coords) of the matching RGB in the default table, and then substitute it with the colour found in the lookup table at XY. I have figured how to pass the Textures from C# into the function, but I am not sure how to find the coords in the default table by matching the colour. Could someone kindly assist? Thanks in advance.

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  • XNA 4: GetData from Texture2D and Set it into Texture3D with specific order

    - by cubrman
    I am trying to convert my color grading 2d lookup texture into 3d LUT. When I simply use: ColorAtlas.GetData(data); ColorAtlas3D.SetData(data); I get this: I tried building my 2d atlass horizontally but it did not helped - the data was messed up in a different way. So my question is how can I influence the order of the data I get from the 2d atlas and how can I properly pass it into my 3d atlas? Update: I know that I can GetData from a specific Rectangular area and put it into several arrays, but the result is still the same. This is what I tried: Color[] data2D = new Color[0]; for (int i = 0; i < 32; i++) { Color[] data = new Color[32 * 32]; GraphicsDevice.SetRenderTarget(null); ColorAtlas.GetData(0, new Rectangle(0, i*32, 32, 32), data, 0, data.Length); int oldLength = data2D.Length; Array.Resize<Color>(ref data2D, oldLength + data.Length); Array.Copy(data, 0, data2D, oldLength, data.Length); } ColorAtlas3D.SetData(data2D);

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  • 3D Camera Problem

    - by Chris
    I allow the user to look around the scene by holding down the left mouse button and moving the mouse. The problem that I have is I can be facing one direction, I move the mouse up and the view tilts up, I move down and the view titles down. If I spin around 180 my left and right still works fine, but when I move the mouse up the view tilts down, and when I move the mouse down the view titles up. This is the code I am using, can anyone see what the problem with the logic is? var viewDir = g_math.subVector(target, g_eye); var rotatedViewDir = []; rotatedViewDir[0] = (Math.cos(g_mouseXDelta * g_rotationDelta) * viewDir[0]) - (Math.sin(g_mouseXDelta * g_rotationDelta) * viewDir[2]); rotatedViewDir[1] = viewDir[1]; rotatedViewDir[2] = (Math.cos(g_mouseXDelta * g_rotationDelta) * viewDir[2]) + (Math.sin(g_mouseXDelta * g_rotationDelta) * viewDir[0]); viewDir = rotatedViewDir; rotatedViewDir[0] = viewDir[0]; rotatedViewDir[1] = (Math.cos(g_mouseYDelta * g_rotationDelta * -1) * viewDir[1]) - (Math.sin(g_mouseYDelta * g_rotationDelta * -1) * viewDir[2]); rotatedViewDir[2] = (Math.cos(g_mouseYDelta * g_rotationDelta * -1) * viewDir[2]) + (Math.sin(g_mouseYDelta * g_rotationDelta * -1) * viewDir[1]); g_lookingDir = rotatedViewDir; var newtarget = g_math.addVector(rotatedViewDir, g_eye);

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  • Why does multiplying texture coordinates scale the texture?

    - by manning18
    I'm having trouble visualizing this geometrically - why is it that multiplying the U,V coordinates of a texture coordinate has the effect of scaling that texture by that factor? eg if you scaled the texture coordinates by a factor of 3 ..then doesn't this mean that if you had texture coordinates 0,1 and 0,2 ...you'd be sampling 0,3 and 0,6 in the U,V texture space of 0..1? How does that make it bigger eg HLSL: tex2D(textureSampler, TexCoords*3) Integers make it smaller, decimals make it bigger I mean I understand intuitively if you added to the U,V coordinates, as that is simply an offset into the sampling range, but what's the case with multiplication? I have a feeling when someone explains this to me I'm going to be feeling mighty stupid

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  • Normals vs Normal maps

    - by KaiserJohaan
    I am using Assimp asset importer (http://assimp.sourceforge.net/lib_html/index.html) to parse 3d models. So far, I've simply pulled out the normal vectors which are defined for each vertex in my meshes. Yet I have also found various tutorials on normal maps... As I understand it for normal maps, the normal vectors are stored in each texel of a normal map, and you pull these out of the normal texture in the shader. Why is there two ways to get the normals, which one is considered best-practice and why?

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  • Why are my 3ds Max .fbx exports huge?

    - by abracadabra1980
    I've made an animation in 3ds Max and want to export it to .fbx and import it into Unity. I've done this once without problems. But this time, my .max file is 2,8MB and my .fbx file came out a huge 630MB! There's nothing wrong with my model: I exported it from a Blender model (to .fbx) and imported it to 3ds max (converted it to an editable poly) to do my rigging and animation. As soon as I import some .bip animations, I get these huge files. Is there a safe way to get smaller file sizes? I don't mind redoing the rigging if I can solve this.

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  • Early Z culling - Ogre

    - by teodron
    This question is concerned with how one can enable this "pixel filter" to work within an Ogre based app. Simply put, one can write two passes, the first without writing any colour values to the frame buffer lighting off colour_write off shading flat The second pass is the one that employs heavy pixel shader computations, hence it would be really nice to get rid of those hidden surface patches and not process them pixel-wise. This approach works, except for one thing: objects with alpha, such as billboard trees suffer in a peculiar way - from one side, they seem to capture the sky/background within their alpha region and ignore other trees/houses behind them, while viewed from the other side, they exhibit the desired behavior. To tackle the issue, I thought I could write a custom vertex shader in the first pass and offset the projected Z component of the vertex a little further away from its actual position, so that in the second pass there is a need to recompute correctly the pixels of the objects closest to the camera. This doesn't work at all, all surfaces are processed in the pixel shader and there is no performance gain. So, if anyone has done a similar trick with Ogre and alpha objects, kindly please help.

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  • How to change speed without changing path travelled?

    - by Ben Williams
    I have a ball which is being thrown from one side of a 2D space to the other. The formula I am using for calculating the ball's position at any one point in time is: x = x0 + vx0*t y = y0 + vy0*t - 0.5*g*t*t where g is gravity, t is time, x0 is the initial x position, vx0 is the initial x velocity. What I would like to do is change the speed of this ball, without changing how far it travels. Let's say the ball starts in the lower left corner, moves upwards and rightwards in an arc, and finishes in the lower right corner, and this takes 5s. What I would like to be able to do is change this so it takes 10s or 20s, but the ball still follows the same curve and finishes in the same position. How can I achieve this? All I can think of is manipulating t but I don't think that's a good idea. I'm sure it's something simple, but my maths is pretty shaky.

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  • ray collision with rectangle and floating point accuracy

    - by phq
    I'm trying to solve a problem with a ray bouncing on a box. Actually it is a sphere but for simplicity the box dimensions are expanded by the sphere radius when doing the collision test making the sphere a single ray. It is done by projecting the ray onto all faces of the box and pick the one that is closest. However because I'm using floating point variables I fear that the projected point onto the surface might be interpreted as being below in the next iteration, also I will later allow the sphere to move which might make that scenario more likely. Also the bounce coefficient might be as low as zero, making the sphere continue along the surface. So my naive solution is to project not only forwards but backwards to catch those cases. That is where I got into problems shown in the figure: In the first iteration the first black arrow is calculated and we end up at a point on the surface of the box. In the second iteration the "back projection" hits the other surface making the second black arrow bounce on the wrong surface. If there are several boxes close to each other this has further consequences making the sphere fall through them all. So my main question is how to handle possible floating point accuracy when placing the sphere on the box surface so it does not fall through. In writing this question I got the idea to have a threshold to only accept back projections a certain amount much smaller than the box but larger than the possible accuracy limitation, this would only cause the "false" back projection when the sphere hit the box on an edge which would appear naturally. To clarify my original approach, the arrows shown in the image is not only the path the sphere travels but is also representing a single time step in the simulation. In reality the time step is much smaller about 0.05 of the box size. The path traveled is projected onto possible sides to avoid traveling past a thinner object at higher speeds. In normal situations the floating point accuracy is not an issue but there are two situations where I have the concern. When the new position at the end of the time step is located very close to the surface, very unlikely though. When using a bounce factor of 0, here it happens every time the sphere hit a box. To add some loss of accuracy, the motivation for my concern, is that the sphere and box are in different coordinate systems and thus the sphere location is transformed for every test. This last one is why I'm not willing to stand on luck that one floating point value lying on top of the box always will be interpreted the same. I did not know voronoi regions by name, but looking at it I'm not sure how it would be used in a projection scenario that I'm using here.

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  • How can I draw an arrow at the edge of the screen pointing to an object that is off screen?

    - by Adam Henderson
    I am wishing to do what is described in this topic: http://www.allegro.cc/forums/print-thread/283220 I have attempted a variety of the methods mentioned here. First I tried to use the method described by Carrus85: Just take the ratio of the two triangle hypontenuses (doesn't matter which triagle you use for the other, I suggest point 1 and point 2 as the distance you calculate). This will give you the aspect ratio percentage of the triangle in the corner from the larger triangle. Then you simply multiply deltax by that value to get the x-coordinate offset, and deltay by that value to get the y-coordinate offset. But I could not find a way to calculate how far the object is away from the edge of the screen. I then tried using ray casting (which I have never done before) suggested by 23yrold3yrold: Fire a ray from the center of the screen to the offscreen object. Calculate where on the rectangle the ray intersects. There's your coordinates. I first calculated the hypotenuse of the triangle formed by the difference in x and y positions of the two points. I used this to create a unit vector along that line. I looped through that vector until either the x coordinate or the y coordinate was off the screen. The two current x and y values then form the x and y of the arrow. Here is the code for my ray casting method (written in C++ and Allegro 5) void renderArrows(Object* i) { float x1 = i->getX() + (i->getWidth() / 2); float y1 = i->getY() + (i->getHeight() / 2); float x2 = screenCentreX; float y2 = ScreenCentreY; float dx = x2 - x1; float dy = y2 - y1; float hypotSquared = (dx * dx) + (dy * dy); float hypot = sqrt(hypotSquared); float unitX = dx / hypot; float unitY = dy / hypot; float rayX = x2 - view->getViewportX(); float rayY = y2 - view->getViewportY(); float arrowX = 0; float arrowY = 0; bool posFound = false; while(posFound == false) { rayX += unitX; rayY += unitY; if(rayX <= 0 || rayX >= screenWidth || rayY <= 0 || rayY >= screenHeight) { arrowX = rayX; arrowY = rayY; posFound = true; } } al_draw_bitmap(sprite, arrowX - spriteWidth, arrowY - spriteHeight, 0); } This was relatively successful. Arrows are displayed in the bottom right section of the screen when objects are located above and left of the screen as if the locations of the where the arrows are drawn have been rotated 180 degrees around the center of the screen. I assumed this was due to the fact that when I was calculating the hypotenuse of the triangle, it would always be positive regardless of whether or not the difference in x or difference in y is negative. Thinking about it, ray casting does not seem like a good way of solving the problem (due to the fact that it involves using sqrt() and a large for loop). Any help finding a suitable solution would be greatly appreciated, Thanks Adam

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  • Problems implementing a screen space shadow ray tracing shader

    - by Grieverheart
    Here I previously asked for the possibility of ray tracing shadows in screen space in a deferred shader. Several problems were pointed out. One of the most important problem is that only visible objects can cast shadows and objects between the camera and the shadow caster can interfere. Still I thought it'd be a fun experiment. The idea is to calculate the view coordinates of pixels and cast a ray to the light. The ray is then traced pixel by pixel to the light and its depth is compared with the depth at the pixel. If a pixel is in front of the ray, a shadow is casted at the original pixel. At first I thought that I could use the DDA algorithm in 2D to calculate the distance 't' (in p = o + t d, where o origin, d direction) to the next pixel and use it in the 3D ray equation to find the ray's z coordinate at that pixel's position. For the 2D ray, I would use the projected and biased 3D ray direction and origin. The idea was that 't' would be the same in both 2D and 3D equations. Unfortunately, this is not the case since the projection matrix is 4D. Thus, some tweak needs to be done to make this work this way. I would like to ask if someone knows of a way to do what I described above, i.e. from a 2D ray in texture coordinate space to get the 3D ray in screen space. I did implement a simple version of the idea which you can see in the following video: video here Shadows may seem a bit pixelated, but that's mostly because of the size of the step in 't' I chose. And here is the shader: #version 330 core uniform sampler2D DepthMap; uniform vec2 projAB; uniform mat4 projectionMatrix; const vec3 light_p = vec3(-30.0, 30.0, -10.0); noperspective in vec2 pass_TexCoord; smooth in vec3 viewRay; layout(location = 0) out float out_AO; vec3 CalcPosition(void){ float depth = texture(DepthMap, pass_TexCoord).r; float linearDepth = projAB.y / (depth - projAB.x); vec3 ray = normalize(viewRay); ray = ray / ray.z; return linearDepth * ray; } void main(void){ vec3 origin = CalcPosition(); if(origin.z < -60) discard; vec2 pixOrigin = pass_TexCoord; //tex coords vec3 dir = normalize(light_p - origin); vec2 texel_size = vec2(1.0 / 600.0); float t = 0.1; ivec2 pixIndex = ivec2(pixOrigin / texel_size); out_AO = 1.0; while(true){ vec3 ray = origin + t * dir; vec4 temp = projectionMatrix * vec4(ray, 1.0); vec2 texCoord = (temp.xy / temp.w) * 0.5 + 0.5; ivec2 newIndex = ivec2(texCoord / texel_size); if(newIndex != pixIndex){ float depth = texture(DepthMap, texCoord).r; float linearDepth = projAB.y / (depth - projAB.x); if(linearDepth > ray.z + 0.1){ out_AO = 0.2; break; } pixIndex = newIndex; } t += 0.5; if(texCoord.x < 0 || texCoord.x > 1.0 || texCoord.y < 0 || texCoord.y > 1.0) break; } } As you can see, here I just increment 't' by some arbitrary factor, calculate the 3D ray and project it to get the pixel coordinates, which is not really optimal. Hopefully, I would like to optimize the code as much as possible and compare it with shadow mapping and how it scales with the number of lights. PS: Keep in mind that I reconstruct position from depth by interpolating rays through a full screen quad.

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  • Move model forward base on model orientation

    - by ChocoMan
    My model rotates on it's own Y-axis regardless of where it is in the world. Here are the controls for the left ThumbStick: UP (move model forward on Z-Axis) DOWN (move model backward on Z-Axis) LEFT & RIGHT (strafe to either side) The problem is adjusting the direction the model's orientation UP and DOWN if the player should also rotate the player while moving forward or backwards. An example what Im trying to achieve would be a car doing donuts. The car is always facing the current direction that it interprets as forward (or rear as backwards) in relation to it's local rotation. Here is how Im calling the movement: // Rotate model with Right Thumbstick along X-Axis modelRotation -= pController.ThumbSticks.Right.X * mRotSpeed; // Move Forward if (pController.IsButtonDown(Buttons.LeftThumbstickUp)) { modelPosition.Z -= -pController.ThumbSticks.Left.Y * speed; } // Move Backward if (pController.IsButtonDown(Buttons.LeftThumbstickDown)) { modelPosition.Z += pController.ThumbSticks.Left.Y * speed; } // Strafe Left if (pController.IsButtonDown(Buttons.LeftThumbstickLeft)) { modelPosition.X += -pController.ThumbSticks.Left.X * speed; } // Strafe Right if (pController.IsButtonDown(Buttons.LeftThumbstickRight)) { modelPosition.X -= pController.ThumbSticks.Left.X * speed; } // DeadZone if (!pController.IsButtonDown(Buttons.LeftThumbstickUp) && !pController.IsButtonDown(Buttons.LeftThumbstickDown) && !pController.IsButtonDown(Buttons.LeftThumbstickLeft) && !pController.IsButtonDown(Buttons.LeftThumbstickRight)) { }

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  • how to implement motion blur effect?

    - by PlayerOne
    I wanted to know how one would implement this motion blur or fade effect behind the soccer ball . Here is what I was thinking . You have the balls current position and you also keep its previous position(couple of sec back). and you draw a "streak" sprite between the 2 points. I have seen this effect lots of time implemented for projects in various 2d games and wanted to know if there is a standard technique. http://i45.tinypic.com/2n24j7r.png

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