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  • Which physics phenomenons can be simulated properly with Box2d or bullet physics? [on hold]

    - by user3585425
    Knowing that box2d or bullet physics can't simulate Newton's cradle (because of multiple bodies being in contact at the same time if I understand correctly), is there a sets of physics phenomenons that imply two or more objects that still can be simulated properly ? For example, I'm thinking about lightweight objects launched towards heavyweight objects. If the object is destroyed on contact, this would not make a difference if the energy is not transmitted correctly on impact.

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  • In OpenGl ES 2, should I allocate multiple transformation matrices?

    - by thm4ter
    In OpenGl ES 2, should I declare just one transformation matrix, and share it across all objects or should I declare a transformation matrix in each object that needs it? for clarification... something like this: public class someclass{ public static float[16] transMatrix = new float[16]; ... public static void translate(int x, int y){ //do translation here } } public class someotherclass{ ... void draw(GL10 unused){ someclass.translate(10,10); //draw } } verses something like this: public class obj1{ public static float[16] transMatrix = new float[16]; ... void draw(GL10 unused){ //translate //draw } } public class obj2{ public static float[16] transMatrix = new float[16]; ... void draw(GL10 unused){ //translate //draw } }

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  • AABB vs OBB Collision Resolution jitter on corners

    - by patt4179
    I've implemented a collision library for a character who is an AABB and am resolving collisions between AABB vs AABB and AABB vs OBB. I wanted slopes for certain sections, so I've toyed around with using several OBBs to make one, and it's working great except for one glaring issue; The collision resolution on the corner of an OBB makes the player's AABB jitter up and down constantly. I've tried a few things I've thought of, but I just can't wrap my head around what's going on exactly. Here's a video of what's happening as well as my code: Here's the function to get the collision resolution (I'm likely not doing this the right way, so this may be where the issue lies): public Vector2 GetCollisionResolveAmount(RectangleCollisionObject resolvedObject, OrientedRectangleCollisionObject b) { Vector2 overlap = Vector2.Zero; LineSegment edge = GetOrientedRectangleEdge(b, 0); if (!SeparatingAxisForRectangle(edge, resolvedObject)) { LineSegment rEdgeA = new LineSegment(), rEdgeB = new LineSegment(); Range axisRange = new Range(), rEdgeARange = new Range(), rEdgeBRange = new Range(), rProjection = new Range(); Vector2 n = edge.PointA - edge.PointB; rEdgeA.PointA = RectangleCorner(resolvedObject, 0); rEdgeA.PointB = RectangleCorner(resolvedObject, 1); rEdgeB.PointA = RectangleCorner(resolvedObject, 2); rEdgeB.PointB = RectangleCorner(resolvedObject, 3); rEdgeARange = ProjectLineSegment(rEdgeA, n); rEdgeBRange = ProjectLineSegment(rEdgeB, n); rProjection = GetRangeHull(rEdgeARange, rEdgeBRange); axisRange = ProjectLineSegment(edge, n); float axisMid = (axisRange.Maximum + axisRange.Minimum) / 2; float projectionMid = (rProjection.Maximum + rProjection.Minimum) / 2; if (projectionMid > axisMid) { overlap.X = axisRange.Maximum - rProjection.Minimum; } else { overlap.X = rProjection.Maximum - axisRange.Minimum; overlap.X = -overlap.X; } } edge = GetOrientedRectangleEdge(b, 1); if (!SeparatingAxisForRectangle(edge, resolvedObject)) { LineSegment rEdgeA = new LineSegment(), rEdgeB = new LineSegment(); Range axisRange = new Range(), rEdgeARange = new Range(), rEdgeBRange = new Range(), rProjection = new Range(); Vector2 n = edge.PointA - edge.PointB; rEdgeA.PointA = RectangleCorner(resolvedObject, 0); rEdgeA.PointB = RectangleCorner(resolvedObject, 1); rEdgeB.PointA = RectangleCorner(resolvedObject, 2); rEdgeB.PointB = RectangleCorner(resolvedObject, 3); rEdgeARange = ProjectLineSegment(rEdgeA, n); rEdgeBRange = ProjectLineSegment(rEdgeB, n); rProjection = GetRangeHull(rEdgeARange, rEdgeBRange); axisRange = ProjectLineSegment(edge, n); float axisMid = (axisRange.Maximum + axisRange.Minimum) / 2; float projectionMid = (rProjection.Maximum + rProjection.Minimum) / 2; if (projectionMid > axisMid) { overlap.Y = axisRange.Maximum - rProjection.Minimum; overlap.Y = -overlap.Y; } else { overlap.Y = rProjection.Maximum - axisRange.Minimum; } } return overlap; } And here is what I'm doing to resolve it right now: if (collisionDetection.OrientedRectangleAndRectangleCollide(obb, player.PlayerCollision)) { var resolveAmount = collisionDetection.GetCollisionResolveAmount(player.PlayerCollision, obb); if (Math.Abs(resolveAmount.Y) < Math.Abs(resolveAmount.X)) { var roundedAmount = (float)Math.Floor(resolveAmount.Y); player.PlayerCollision._position.Y -= roundedAmount; } else if (Math.Abs(resolveAmount.Y) <= 30.0f) //Catch cases where the player should be able to step over the top of something { var roundedAmount = (float)Math.Floor(resolveAmount.Y); player.PlayerCollision._position.Y -= roundedAmount; } else { var roundedAmount = (float)Math.Floor(resolveAmount.X); player.PlayerCollision._position.X -= roundedAmount; } } Can anyone see what might be the issue here, or has anyone experienced this before that knows a possible solution? I've tried for a few days to figure this out on my own, but I'm just stumped.

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  • PhysX Capsule Character Controller floating above ground

    - by Jannie
    I am using PhysX Version 3.0.2 in the simulation package I'm working on, and I've encountered some bizarre behavior with the capsule character controller. When I set the controller's height and radius to the appropriate values (r = 0.25, h = 1.86)it behaves correctly (moving along the ground, colliding with other objects, and so on) except that the capsule itself is floating above the ground. The actor will then bump his head when trying to get through a door, since the capsule is the correct height but also floating above the ground. This image should illustrate what I'm going on about: One can clearly see that the rest of the scene has their collision bodies wrapped correctly, it's just the capsule that's going wrong! The stop-gap I've implemented is creating a smaller capsule and giving it an offset, but I need to implement ray-picking for the controller next so the capsule has to surround the character model properly. Here's my character creation code (with height = 1.86f and radius = 0.25f): NxController* D3DPhysXManager::CreateCharacterController( std::string l_stdsControllerName, float l_fHeight, float l_fRadius, D3DXVECTOR3 l_v3Position ) { NxCapsuleControllerDesc l_CapsuleControllerDescription; l_CapsuleControllerDescription.height = l_fHeight; l_CapsuleControllerDescription.radius = l_fRadius; l_CapsuleControllerDescription.position.set( l_v3Position.x, l_v3Position.y, l_v3Position.z ); l_CapsuleControllerDescription.callback = &this->m_ControllerHitReport; NxController* l_pController = this->m_pControllerManager->createController( this->m_pScene, l_CapsuleControllerDescription ); this->m_pControllerMap.insert( l_ControllerValuePair( l_stdsControllerName, l_pController ) ); return l_pController; } Any help at all would be appreciated, I just can't figure this one out! P.S. I've found a couple of (rather old) threads describing the same issue, but it seems they couldn't find a solution either. Here are the links: http://forum-archive.developer.nvidia.com/index.php?showtopic=6409 http://forum-archive.developer.nvidia.com/index.php?showtopic=3272 http://www.ogre3d.org/addonforums/viewtopic.php?f=8&t=23003

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  • 3D physics engine for accurate collision handling on desktop/laptop computers (non-console)

    - by Georges Oates Larsen
    What are your suggestions for a physics engine that satisfies the following criteria? Capable of calculating collisions between multiple concave mesh-based colliders Handles many collisions going on at once (for instance one mesh being wedged between two others, which themselves may be wedged between two meshes) Does not allow for collider passthrough, even at high speeds. For instance, if I am applying force to a programmatically hinged object that makes it spin, I do not want it to pass through another rigidbody that it collides with while spinning. I have this problem using PhysX As implied before, reacts well to hinged objects, preferably has its own implementation of a hinge, but I am willing to program my own. The important part is that it has some sort of interface that guarantees accurate collision tracking even when dealing with these things Platform independent -- runs on mac as well as PC, also not tied down to specific graphics cards I think that's the best way to explain what I am looking for. Basically, I need SUPER reliable collisions. Something that can't be accomplished with a simple ray casting approach that sends a ray from the last position of the object to the current position (as this object may be potentially large and colliding with small objects via rotation) Bonus points for also including an OPEN SOURCE engine.

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  • swf file not playing aftre being published

    - by rsquare
    i am trying to run the 'connector' example that comes bundled with smartfoxserver2x downloads..there it connects to the server and loads the correct configuration file. when i run it in adobe flash professional 5,it runs correctly and connects to the server but after being published as SWF movie,it doesnt work.it loads the configuration file but cant connect and gives error connection failure..ERROR 2048 this is the example i am talking about. http://docs2x.smartfoxserver.com/ExamplesFlash/connector

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  • Spherical to Cartesian Coordinates

    - by user1258455
    Well I'm reading the Frank's Luna DirectX10 book and, while I'm trying to understand the first demo, I found something that's not very clear at least for me. In the updateScene method, when I press A, S, W or D, the angles mTheta and mPhi change, but after that, there are three lines of code that I don't understand exactly what they do: // Convert Spherical to Cartesian coordinates: mPhi measured from +y // and mTheta measured counterclockwise from -z. float x = 5.0f*sinf(mPhi)*sinf(mTheta); float z = -5.0f*sinf(mPhi)*cosf(mTheta); float y = 5.0f*cosf(mPhi); I mean, this explains that they do, it says that it converts the spherical coordinates to cartesian coordinates, but, mathematically, why? why the x value is calculated by the product of the sins of both angles? And the z by the product of the sine and cosine? and why the y just uses the cosine? After that, those values (x, y and z) are used to build the view matrix. The book doesn't explain (mathematically) why those values are calculated like that (and I didn't find anything to help me to understand it at the first Part of the book: "Mathematical prerequisites"), so it would be good if someone could explain me what exactly happen in those code lines or just give me a link that helps me to understand the math part. Thanks in advance!

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  • HLSL Shader not working right?

    - by dvds414
    Okay so I have this shader for ambient occlusion. It loads to world correctly, but it just shows all the models as being white. I do not know why. I am just running the shader while the model is rendering, is that correct? or do I need to make a render target or something? if so then how? I'm using C++. Here is my shader. float sampleRadius; float distanceScale; float4x4 xProjection; float4x4 xView; float4x4 xWorld; float3 cornerFustrum; struct VS_OUTPUT { float4 pos : POSITION; float2 TexCoord : TEXCOORD0; float3 viewDirection : TEXCOORD1; }; VS_OUTPUT VertexShaderFunction( float4 Position : POSITION, float2 TexCoord : TEXCOORD0) { VS_OUTPUT Out = (VS_OUTPUT)0; float4 WorldPosition = mul(Position, xWorld); float4 ViewPosition = mul(WorldPosition, xView); Out.pos = mul(ViewPosition, xProjection); Position.xy = sign(Position.xy); Out.TexCoord = (float2(Position.x, -Position.y) + float2( 1.0f, 1.0f ) ) * 0.5f; float3 corner = float3(-cornerFustrum.x * Position.x, cornerFustrum.y * Position.y, cornerFustrum.z); Out.viewDirection = corner; return Out; } texture depthTexture; texture randomTexture; sampler2D depthSampler = sampler_state { Texture = <depthTexture>; ADDRESSU = CLAMP; ADDRESSV = CLAMP; MAGFILTER = LINEAR; MINFILTER = LINEAR; }; sampler2D RandNormal = sampler_state { Texture = <randomTexture>; ADDRESSU = WRAP; ADDRESSV = WRAP; MAGFILTER = LINEAR; MINFILTER = LINEAR; }; float4 PixelShaderFunction(VS_OUTPUT IN) : COLOR0 { float4 samples[16] = { float4(0.355512, -0.709318, -0.102371, 0.0 ), float4(0.534186, 0.71511, -0.115167, 0.0 ), float4(-0.87866, 0.157139, -0.115167, 0.0 ), float4(0.140679, -0.475516, -0.0639818, 0.0 ), float4(-0.0796121, 0.158842, -0.677075, 0.0 ), float4(-0.0759516, -0.101676, -0.483625, 0.0 ), float4(0.12493, -0.0223423, -0.483625, 0.0 ), float4(-0.0720074, 0.243395, -0.967251, 0.0 ), float4(-0.207641, 0.414286, 0.187755, 0.0 ), float4(-0.277332, -0.371262, 0.187755, 0.0 ), float4(0.63864, -0.114214, 0.262857, 0.0 ), float4(-0.184051, 0.622119, 0.262857, 0.0 ), float4(0.110007, -0.219486, 0.435574, 0.0 ), float4(0.235085, 0.314707, 0.696918, 0.0 ), float4(-0.290012, 0.0518654, 0.522688, 0.0 ), float4(0.0975089, -0.329594, 0.609803, 0.0 ) }; IN.TexCoord.x += 1.0/1600.0; IN.TexCoord.y += 1.0/1200.0; normalize (IN.viewDirection); float depth = tex2D(depthSampler, IN.TexCoord).a; float3 se = depth * IN.viewDirection; float3 randNormal = tex2D( RandNormal, IN.TexCoord * 200.0 ).rgb; float3 normal = tex2D(depthSampler, IN.TexCoord).rgb; float finalColor = 0.0f; for (int i = 0; i < 16; i++) { float3 ray = reflect(samples[i].xyz,randNormal) * sampleRadius; //if (dot(ray, normal) < 0) // ray += normal * sampleRadius; float4 sample = float4(se + ray, 1.0f); float4 ss = mul(sample, xProjection); float2 sampleTexCoord = 0.5f * ss.xy/ss.w + float2(0.5f, 0.5f); sampleTexCoord.x += 1.0/1600.0; sampleTexCoord.y += 1.0/1200.0; float sampleDepth = tex2D(depthSampler, sampleTexCoord).a; if (sampleDepth == 1.0) { finalColor ++; } else { float occlusion = distanceScale* max(sampleDepth - depth, 0.0f); finalColor += 1.0f / (1.0f + occlusion * occlusion * 0.1); } } return float4(finalColor/16, finalColor/16, finalColor/16, 1.0f); } technique SSAO { pass P0 { VertexShader = compile vs_3_0 VertexShaderFunction(); PixelShader = compile ps_3_0 PixelShaderFunction(); } }

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  • Client side prediction/simulation Question

    - by Legendre
    I found a related question but it doesn't have what I needed. Client A sends input to move at T0. Server receives input at T1. All clients receive the change at T2. Question: With client-side prediction, client A would start moving at T0, client-side. All other clients receive the change at T2, so to them, client A only started moving at T2. If I understand correctly, client B will always see client A's past position and not his current position? How do I sync both client B and client A?

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  • OpenGL - Rendering from part of an index and vertex array depending on an element count

    - by user1423893
    I'm currently drawing my shapes as lines by using a VAO and then assigning the dynamic vertices and indices each frame. // Bind VAO glBindVertexArray(m_vao); // Update the vertex buffer with the new data (Copy data into the vertex buffer object) glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(VertexPosition), m_vertices.data(), GL_DYNAMIC_DRAW); // Update the index buffer with the new data (Copy data into the index buffer object) glBufferData(GL_ELEMENT_ARRAY_BUFFER, numIndices * sizeof(unsigned short), indices.data(), GL_DYNAMIC_DRAW); glDrawElements(GL_LINES, numIndices, GL_UNSIGNED_SHORT, BUFFER_OFFSET(0)); // Unbind VAO glBindVertexArray(0); What I would like to do is draw the lines using only part of the data stored in the index and vertex buffer objects. The vertex buffer has its vertices set from an array of defined maximum size: std::array<VertexPosition, maxVertices> m_vertices; The index buffer has its elements set from an array of defined maximum size: std::array<unsigned short, maxIndices> indices = { 0 }; A running total is kept of the number of vertices and indices needed for each draw call numVertices numIndices Can I not specify that the buffer data contain the entire array and only read from part of it when drawing? For example using the vertex buffer object glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(VertexPosition), m_vertices.data(), GL_DYNAMIC_DRAW); m_vertices.data() = Entire array is stored numVertices * sizeof(VertexPosition) = Amount of data to read from the entire array Is this not the correct way to approach this? I do not wish to use std::vector if possible.

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  • Given a start and end point, how can I constrain the end point so the resulting line segment is horizontal, vertical, or 45 degrees?

    - by GloryFish
    I have a grid of letters. The player clicks on a letter and drags out a selection. Using Bresenham's Algorithm I can create a line of highlighted letters representing the player's selection. However, what I really want is to have the line segment be constrained to 45 degree angles (as is common for crossword-style games). So, given a start point and an end point, how can I find the line that passes through the start point and is closest to the end point? Bonus: To make things super sweet I'd like to get a list of points in the grid that the line passes through, and for super MEGA bonus points, I'd like to get them in order of selection (i.e. from start point to end point).

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  • Can't change color of sprites in unity

    - by Aceleeon
    I would like to create a script that targets a 2d sprite "enemy" and changes their color to red (slightly opaque red if possible) when you hit tab. I have this code from a 3d tutorial hoping the transition would work. But it does not. I only get the script to cycle the enemy tags but never changes the color of the sprite. I have the code below I'm very new to coding, and any help would be FANTASTIC! HELP! hahah. TL;DR Cant get 3d color targeting to work for 2D. Check out the c#code below using UnityEngine; using System.Collections; using System.Collections.Generic; public class Targetting : MonoBehaviour { public List targets; public Transform selectedTarget; private Transform myTransform; // Use this for initialization void Start () { targets = new List(); selectedTarget = null; myTransform = transform; AddAllEnemies(); } public void AddAllEnemies() { GameObject[] go = GameObject.FindGameObjectsWithTag("Enemy"); foreach(GameObject enemy in go) AddTarget(enemy.transform); } public void AddTarget(Transform enemy) { targets.Add(enemy); } private void SortTargetsByDistance() { targets.Sort(delegate(Transform t1,Transform t2) { return Vector3.Distance(t1.position, myTransform.position).CompareTo(Vector3.Distance(t2.position, myTransform.position)); }); } private void TargetEnemy() { if(selectedTarget == null) { SortTargetsByDistance(); selectedTarget = targets[0]; } else { int index = targets.IndexOf(selectedTarget); if(index < targets.Count -1) { index++; } else { index = 0; } selectedTarget = targets[index]; } } private void SelectTarget() { selectedTarget.GetComponent().color = Color.red; } private void DeselectTarget() { selectedTarget.GetComponent().color = Color.blue; selectedTarget = null; } // Update is called once per frame void Update() { if(Input.GetKeyDown(KeyCode.Tab)) { TargetEnemy(); } } }

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  • Which 3D file formats support multiple animations? [on hold]

    - by Justin
    I'm working on a 3D application that uses Assimp to import 3D models with animations. Personally, I use Blender to create the models and animations. I'm having trouble exporting multiple animations, however. For example, I'd like to have an idle animation, a walk animation, a run animation, etc. So far I've tried COLLADA and DirectX without much success. The COLLADA export will include the first animation, but not any of the others. The DirectX doesn't include any animation. Which 3D file formats support multiple animations? (Preferably one that Assimp can import. Also, the Assimp website says that it doesn't support .blend files with animation, otherwise I'd just do that.)

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  • How to make natural-looking paths with A* on a grid?

    - by user11177
    I've been reading this: http://theory.stanford.edu/~amitp/GameProgramming/Heuristics.html But there are some things I don't understand, for example the article says to use something like this for pathfinding with diagonal movement: function heuristic(node) = dx = abs(node.x - goal.x) dy = abs(node.y - goal.y) return D * max(dx, dy) I don't know how do set D to get a natural looking path like in the article, I set D to the lowest cost between adjacent squares like it said, and I don't know what they meant by the stuff about the heuristic should be 4*D, that does not seem to change any thing. This is my heuristic function and move function: def heuristic(self, node, goal): D = 10 dx = abs(node.x - goal.x) dy = abs(node.y - goal.y) return D * max(dx, dy) def move_cost(self, current, node): cross = abs(current.x - node.x) == 1 and abs(current.y - node.y) == 1 return 19 if cross else 10 Result: The smooth sailing path we want to happen: The rest of my code: http://pastebin.com/TL2cEkeX

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  • How can I ease the work of getting pixel coordinates from a spritesheet?

    - by ThePlan
    When it comes to spritesheets they're usually easier to use, and they're very efficient memory-wise, but the problem that I'm always having is getting the actual position of a sprite from a sheet. Usually, I have to throw in some aproximated values and modify them several times until I get it right. My question: is there a tool which can basically show you the coordinates of the mouse relative to the image you have opened? Or is there a simpler method of getting the exact rectangle that the sprite is contained in?

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  • Weird appearance for a 3D XNA ground

    - by Belos
    I wanted to add a ground so I can know the position of a helicopter in the world. But the ground appeared in a weird way: http://i.stack.imgur.com/yTSuW.jpg The ground had the following texture: http://i.stack.imgur.com/pdpxB.png EDIT: Sorry, I forgot to post the code: public class ImportModel { public Vector3 Position { get; set; } public Vector3 Rotation { get; set; } public Vector3 Scale { get; set; } Model Model; Matrix[] modeltransforms; GraphicsDevice GraphicDevice; ContentManager Content; BoundingSphere sphere; bool boundingimplemented = false; public ImportModel(string model, GraphicsDevice gd, ContentManager cm, Vector3 position, Vector3 rot, Vector3 sca) { GraphicDevice = gd; Content = cm; Position = position; Rotation = rot; Scale = sca; Model = Content.Load<Model>(model); modeltransforms = new Matrix[Model.Bones.Count]; Model.CopyAbsoluteBoneTransformsTo(modeltransforms); } public void Draw(Camera camera) { Matrix baseworld = Matrix.CreateScale(Scale) * Matrix.CreateFromYawPitchRoll(Rotation.Y, Rotation.X, Rotation.Z) * Matrix.CreateTranslation(Position); foreach (ModelMesh mesh in Model.Meshes) { Matrix localworld = modeltransforms[mesh.ParentBone.Index] * baseworld; foreach (ModelMeshPart meshpart in mesh.MeshParts) { BasicEffect effect = (BasicEffect)meshpart.Effect; effect.World = localworld; effect.View = camera.View; effect.Projection = camera.Projection; effect.EnableDefaultLighting(); } mesh.Draw(); } } public BoundingSphere BoundingSphere { get { if (!boundingimplemented) { foreach (ModelMesh mesh in Model.Meshes) { BoundingSphere transformed = mesh.BoundingSphere.Transform( modeltransforms[mesh.ParentBone.Index]); sphere = BoundingSphere.CreateMerged(sphere, transformed); } Matrix worldTransform = Matrix.CreateScale(Scale) * Matrix.CreateTranslation(Position); BoundingSphere transforme = sphere; transforme = transforme.Transform(worldTransform); return transforme; } else { Matrix worldTransform = Matrix.CreateScale(Scale) * Matrix.CreateTranslation(Position); BoundingSphere transformed = sphere; transformed = transformed.Transform(worldTransform); return transformed; } } } } Then I call the class from the Game1 class: ImportModel ground = new ImportModel("ground", GraphicsDevice, Content, Vector3.Zero, Vector3.Zero, new Vector3(20f)); EDIT2:This is how the scene looks from top: i.stack.imgur.com/Hs983.jpg

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  • Adding root bone in 3DS Max?

    - by carlturtle
    my animation artist has made me a nice first person pair of arms, animated it, textured it, and given it to me. Then he went on vacation. I am programming my animations, and I am trying to test the model he has given me. Building my project gives me a warning: Multiple skeletons were found in the file. The first skeleton, named "frame l upperarm" has been moved to be a child of the scene root. The other, "frame r upperarm", will be ignored. Fragment identifier "frame r upperarm". Then an error: "Vertex is bound to bone "frame l forearm", but this bone is not present in the skeleton." I realize this means that there are two skeletons, as said in this problem: Importing 3d model with multiple skeletons I have 3DS Max, but I have no idea how to use it, and Google/CGTalk/Plycount turn up nothing relevant on how to add a root bone or combine skeletons. If anyone knows how, it would help me out greatly. Thanks.

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  • Java enum pairs / "subenum" or what exactly?

    - by vemalsar
    I have an RPG-style Item class and I stored the type of the item in enum (itemType.sword). I want to store subtype too (itemSubtype.long), but I want to express the relation between two data type (sword can be long, short etc. but shield can't be long or short, only round, tower etc). I know this is wrong source code but similar what I want: enum type { sword; } //not valid code! enum swordSubtype extends type.sword { short, long } Question: How can I define this connection between two data type (or more exactly: two value of the data types), what is the most simple and standard way? Array-like data with all valid (itemType,itemSubtype) enum pairs or (itemType,itemSubtype[]) so more subtype for one type, it would be the best. OK but how can I construct this simplest way? Special enum with "subenum" set or second level enum or anything else if it does exists 2 dimensional "canBePairs" array, itemType and itemSubtype dimensions with all type and subtype and boolean elements, "true" means itemType (first dimension) and itemSubtype (second dimension) are okay, "false" means not okay Other better idea Thank you very much!

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  • how to keep display tick rate steady when using continuous collision detection?

    - by nas Ns
    (I've just found about this forum). I hope it is ok to repost my question again here. I posted this question at stackoverflow, but it looks like I might get better help here. Here is the question: I've implemented basic particles motion simulation with continuous collision detection. But there is small issue in display. Assume simple case of circles moving inside square. All elastic collisions. no firction. All motion is constant speed. No forces are involved, no gravity. So when a particle is moving, it is always moving at constant speed (in between collisions) What I do now is this: Let the simulation time step be 1 second (for example). This is the time step simulation is advanced before displaying the new state (unless there is a collision sooner than this). At start of each time step, time for the next collision between any particles or a particle with a wall is determined. Call this the TOC time; let’s say TOC was .5 seconds in this case. Since TOC is smaller than the standard time step, then the system is moved by TOC and the new system is displayed so that the new display shows any collisions as just taking place (say 2 circles just touched each other’s, or a circle just touched a wall) Next, the collision(s) are resolved (i.e. speeds updated, changed directions etc..). A new step is started. The same thing happens. Now assume there is no collision detected within the next 1 second (those 2 circles above will not be in collision any more, even though they are still touching, due to their speeds showing they are moving apart now), Hence, simulation time is advanced now by the full one second, the standard time step, and particles are moved on the screen using 1 second simulation time and new display is shown. You see what has just happened: One frame ran for .5 seconds, but the next frame runs for 1 second, may be the 3rd frame is displayed after 2 seconds, may be the 4th frame is displayed after 2.8 seconds (because TOC was .8 seconds then) and so on. What happens is that the motion of a particle on the screen appears to speed up or slow down, even though it is moving at constant speed and was not even involved in a collision. i.e. Looking at one particle on its own, I see it suddenly speeding up or slowing down, becuase another particle had hit a wall. This is because the display tick is not uniform. i.e. the frame rate update is changing, giving the false illusion that a particle is moving at non-constant speed while in fact it is moving at constant speed. The motion on the screen is not smooth, since the screen is not updating at constant rate. I am not able to figure how to fix this. If I want to show 2 particles at the moment of the collision, I must draw the screen at different times. Drawing the screen always at the same tick interval, results in seeing 2 particles before the collision, and then after the collision, and not just when they colliding, which looked bad when I tried it. So, how do real games handle this issue? How to display things in order to show collisions when it happen, yet keep the display tick constant? These 2 requirements seem to contradict each other’s.

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  • What has the most efficient intersection test against an AABB tree - OBB, Cylinder or Capsule?

    - by identitycrisisuk
    I'm currently trying to find collisions in 3D between a tighter volume than an AABB and a tree of AABB volumes. I just need to know whether they are intersecting, no closest distance or collision response. An OBB, Cylinder or Capsule would all roughly fit these purposes but Cylinder and Capsule were the first thing I thought of, which I have found little information about detecting intersections online. Am I right in thinking that they would always be more complex to perform Separating Axis Tests on even though they might seem like simpler shapes? I figure by the time I get my head around SAT for curved shapes I could have done the thing with OBBs but I wanted to find out for sure.

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  • node.js callback getting unexpected value for variable

    - by defrex
    I have a for loop, and inside it a variable is assigned with var. Also inside the loop a method is called which requires a callback. Inside the callback function I'm using the variable from the loop. I would expect that it's value, inside the callback function, would be the same as it was outside the callback during that iteration of the loop. However, it always seems to be the value from the last iteration of the loop. Am I misunderstanding scope in JavaScript, or is there something else wrong? The program in question here is a node.js app that will monitor a working directory for changes and restart the server when it finds one. I'll include all of the code for the curious, but the important bit is the parse_file_list function. var posix = require('posix'); var sys = require('sys'); var server; var child_js_file = process.ARGV[2]; var current_dir = __filename.split('/'); current_dir = current_dir.slice(0, current_dir.length-1).join('/'); var start_server = function(){ server = process.createChildProcess('node', [child_js_file]); server.addListener("output", function(data){sys.puts(data);}); }; var restart_server = function(){ sys.puts('change discovered, restarting server'); server.close(); start_server(); }; var parse_file_list = function(dir, files){ for (var i=0;i<files.length;i++){ var file = dir+'/'+files[i]; sys.puts('file assigned: '+file); posix.stat(file).addCallback(function(stats){ sys.puts('stats returned: '+file); if (stats.isDirectory()) posix.readdir(file).addCallback(function(files){ parse_file_list(file, files); }); else if (stats.isFile()) process.watchFile(file, restart_server); }); } }; posix.readdir(current_dir).addCallback(function(files){ parse_file_list(current_dir, files); }); start_server(); The output from this is: file assigned: /home/defrex/code/node/ejs.js file assigned: /home/defrex/code/node/templates file assigned: /home/defrex/code/node/web file assigned: /home/defrex/code/node/server.js file assigned: /home/defrex/code/node/settings.js file assigned: /home/defrex/code/node/apps file assigned: /home/defrex/code/node/dev_server.js file assigned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js For those from the future: node.devserver.js

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  • Pathfinding with MicroPather : costs calculations with sectors and portals

    - by Adan
    Hello, I'm considering using micropather to help me with pathfinding. I'm not using a discrete map : I'm working in 2d with sectors and portales. However, I'm just wondering what is the best way to compute costs with this library in this context. Just to be more clear about geometrical shapes I'm using : sectors are basically convex polygons, and portals are segments that lies on sector's edge. Micropather exposes a pure virtual Graph class that you must inherate and overrides 3 functions. I understand how pathfinding works, so there's no problem in overriding those functions. Right now, my implementation give me results, i.e I'm able to find a path in my map, but I'm not sure I'm using an optimal solution. For the AdjacentCost method : I just take the distance between sector's centers as the cost. I think a better solution should be to use the portal between the two sectors, compute its center, and then the cost should be : distance( sector A center, portal center ) + distance ( sector B center, portal center ). I'm pretty sure the approximation I'm using with just sector's center is enough for most cases, but maybe with thin and long sectors that are perpendicular, this approximation could mislead the A* algorithm. For the LeastCostEstimate method : I just take the midpoint of the two sectors. So, as you understand, I'm always working with sectors' centers, and it's working fine. And I'm pretty sure there's a better way to work. Any suggestions or feedbacks? Thanks in advance!

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  • Colored Collision Detection

    - by tugrul büyükisik
    Several years ago, i made a fast collision detection for 2D, it was just checking a bullets front-pixel's color to check if it were to hit something. Lets say the target rgb color is (124,200,255) then it just checks for that color. After the collision detection, it paints the target with appropriate picture. So, collision detection is made in background without drawing but then painted and drawed. How can i do this in 3D? Because, a vertex is not just exist like a 2D picture's pixel. I looked at some java3D and other programs and understood that 3D world is made of objects. Not just pictures. Is there a program that truly fills the world with vertices ? But it could be needing terabytes of ram even more. Do you know an easy way to interpolate the color of a vertex in java3D or similar program? Note: for a rgb color-identifier, i can make 255*255*255 different 2D objects in background.

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  • Writing a basic shader for large input files

    - by Zoltan Varadi
    I started writing a shader for my iOS app and instead of starting from scratch i used this tutorial here: http://www.raywenderlich.com/3664/opengl-es-2-0-for-iphone-tutorial I wrote an import function, first to import wavefront .obj models. My problem is that with I can't handle larger inputs (with a simple cube it was working). I realized that the indices array is an array of GLubyte values, which is unsigned char, so as a result i cant have more than 256 indexes. I modified it to GLuint, but then only get a blank screen. What else needs to me modified? p.s.: the source can be downloaded from here: http://d1xzuxjlafny7l.cloudfront.net/downloads/HelloOpenGL.zip

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  • How can I model a pendulum blade?

    - by Micah Delane Bolen
    Like this one from Saw V: What primitive shape/s would you start out with? How would you transform the primitive shape/s to give it a nice, smooth, sharp blade on one side without distorting the entire object in a weird way? I tried starting out with a cylinder and then subtracting the top half using a duplicate cylinder and a difference modifier, but I ended up distorting the entire object when I tried to pull the "blade" edges together. I think I need to add lattices to smoothly "sharpen" the edge of the blade.

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