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• If I use my own normal values, should I turn off winding order culling?

  - by Phil

  I've discovered that I managed to program a series of boxes with indexed vertices in such a way that every other triangle (Half of each face) has a backwards winding order. As a result, XNA is culling half of them. However, my Vertex objects contain normal data that I have explicitly set, and I am going to implement my own backface culling shortly to reduce the size of the VertexBuffer. Should I turn off winding order culling and manage it myself, or should I make sure the winding order is consistent and let XNA handle it?

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

  - by Chan

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

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• Seeking an C/C++ OBJ geometry read/write that does not modify the representation

  - by Blake Senftner

  I am seeking a means to read and write OBJ geometry files with logic that does not modify the geometry representation. i.e. read geometry, immediately write it, and a diff of the source OBJ and the one just written will be identical. Every OBJ writing utility I've been able to find online fails this test. I am writing small command line tools to modify my OBJ geometries, and I need to write my results, not just read the geometry for rendering purposes. Simply needing to write the geometry knocks out 95% of the OBJ libraries on the web. Also, many of the popular libraries modify the geometry representation. For example, Nat Robbin's GLUT library includes the GLM library, which both converts quads to triangles, as well as reverses the topology (face ordering) of the geometry. It's still the same geometry, but if your tool chain expects a given topology, such as for rigging or morph targets, then GLM is useless. I'm not rendering in these tools, so dependencies like OpenGL or GLUT make no sense. And god forbid, do not "optimize" the geometry! Redundant vertices are on purpose for maintaining oneself on cache with our weird little low memory mobile devices.

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• Procedural Mesh: UV mapping

  - by Esa

  I made a procedural mesh and now I want to apply a texture to it. The problem is, I cannot get it to stick the way I want it to. The idea is to have the texture painted only once over the whole mesh, so that there is no repeating. How should I map the UV to make that happen? My mesh is a simple plane consisting of 56 triangles. I'd add pictures to clear things up but I cannot since my reputation is below 10 points. Any help is appreciated. EDIT(Kind people gave me up votes, thank you): Meet my mesh: And when textured(tried to repeat the texture): And my texture:

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• First Minecraft mod not working: make a new sword

  - by yamikoWebs

  I am making my first mod and cannot see what is wrong with it. I am using MCP and Modloader. For my first mod I was going to make swords. I started with making a new EnumToolMaterials WOOD(0, 59, 2.0F, 0, 15), STONE(1, 131, 4.0F, 1, 5), IRON(2, 250, 6.0F, 2, 14), LAPIS(3, 750, 7.0F, 2, 14), OBSIDIAN(3, 1000, 7.5F, 3, 12), EMERALD(3, 1561, 8.0F, 3, 10),//diamond GREEN(3, 2000, 9.0F, 4, 10),//emerald GOLD(0, 200, 12.0F, 0, 22); then here is the mod class public class _Mod_Yamiko extends BaseMod{ /* mod itemts */ public static final Item swordLapis = (new ItemSword(600, EnumToolMaterial.LAPIS)).setItemName("swordLapis"); public static final Item swordObsidian = (new ItemSword(601, EnumToolMaterial.OBSIDIAN)).setItemName("swordObsidian"); public static final Item swordGreen = (new ItemSword(602, EnumToolMaterial.GREEN)).setItemName("swordGreen"); public void load(){ //set images swordLapis.iconIndex = ModLoader.addOverride("/gui/items.png","/gui/swordLapis.png"); ModLoader.addName(swordLapis, "Lapis Sword"); //craft ModLoader.addRecipe(new ItemStack(_Mod_Yamiko.swordLapis, 1), new Object[]{ " X ", " X ", " Y ", 'X', Block.dirt, 'Y', Item.stick }); } public String getVersion(){ return "0.1"; } } Then I made a 16×16 .png image. I am not sure where to save it so I recompiled and reobfuscated, took the mod files and put it in my local Minecraft install, added the image where it be should be. No problems when playing but I cannot make the new sword.

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• Wikipedia A* pathfinding algorithm takes a lot of time

  - by Vee

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

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• Marketing: Angry Birds - How it's done

  - by John

  Why do some apps, like Angry Birds, dominate the market while other cool/fun/addicting apps are never heard of? I'm trying to figure out the best marketing strategy, or best way to sell an app to mass market. Does anybody have any ideas or things they noticed about the marketing of major blockbuster apps, like Angry Birds, why they get so popular and stay at the top of charts. Thanks for any ideas, comments ...

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• Importing a windows project into android using cocos2d-x

  - by Ef Es

  What I am trying to do today is to import a full project to Android, but no tutorials are available for that that I have seen. My approach was to create a new android project, copy all the classes and resources in the folders and calling ./build_native.sh but I get an error because most of the files are not being included in the project. I tried opening the Android.mk and I can see why "LOCAL_SRC_FILES := AppDelegate.cpp \ HelloWorldScene.cpp" are the only files linked. Should I manually modify the make file or can it be automated by some way I don't know? Thank you. UPDATE: I manually added all files and headers to the make file and I get errors linking Box2D or cocosdenshion libraries.

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• 2D metaball liquid effect - how to feed output of one rendering pass as input to another shader

  - by Guye Incognito

  I'm attempting to make a shader for unity3d web project. I want to implement something like in the great answer by DMGregory in this question. in order to achieve a final look something like this.. Its metaballs with specular and shading. The steps to make this shader are. 1. Convert the feathered blobs into a heightmap. 2. Generate a normalmap from the heightmap 3. Feed the normal map and height map into a standard unity shader, for instance transparent parallax specular. I pretty much have all the pieces I need assembled but I am new to shaders and need help putting them together I can generate a heightmap from the blobs using some fragment shader code I wrote (I'm just using the red channel here cus i dont know if you can access the brightness) half4 frag (v2f i) : COLOR{ half4 texcol,finalColor; texcol = tex2D (_MainTex, i.uv); finalColor=_MyColor; if(texcol.r<_botmcut) { finalColor.r= 0; } else if((texcol.r>_topcut)) { finalColor.r= 0; } else { float r = _topcut-_botmcut; float xpos = _topcut - texcol.r; finalColor.r= (_botmcut + sqrt((xpos*xpos)-(r*r)))/_constant; } return finalColor; } turns these blobs.. into this heightmap Also I've found some CG code that generates a normal map from a height map. The bit of code that makes the normal map from finite differences is here void surf (Input IN, inout SurfaceOutput o) { o.Albedo = fixed3(0.5); float3 normal = UnpackNormal(tex2D(_BumpMap, IN.uv_MainTex)); float me = tex2D(_HeightMap,IN.uv_MainTex).x; float n = tex2D(_HeightMap,float2(IN.uv_MainTex.x,IN.uv_MainTex.y+1.0/_HeightmapDimY)).x; float s = tex2D(_HeightMap,float2(IN.uv_MainTex.x,IN.uv_MainTex.y-1.0/_HeightmapDimY)).x; float e = tex2D(_HeightMap,float2(IN.uv_MainTex.x-1.0/_HeightmapDimX,IN.uv_MainTex.y)).x; float w = tex2D(_HeightMap,float2(IN.uv_MainTex.x+1.0/_HeightmapDimX,IN.uv_MainTex.y)).x; float3 norm = normal; float3 temp = norm; //a temporary vector that is not parallel to norm if(norm.x==1) temp.y+=0.5; else temp.x+=0.5; //form a basis with norm being one of the axes: float3 perp1 = normalize(cross(norm,temp)); float3 perp2 = normalize(cross(norm,perp1)); //use the basis to move the normal in its own space by the offset float3 normalOffset = -_HeightmapStrength * ( ( (n-me) - (s-me) ) * perp1 + ( ( e - me ) - ( w - me ) ) * perp2 ); norm += normalOffset; norm = normalize(norm); o.Normal = norm; } Also here is the built-in transparent parallax specular shader for unity. Shader "Transparent/Parallax Specular" { Properties { _Color ("Main Color", Color) = (1,1,1,1) _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 0) _Shininess ("Shininess", Range (0.01, 1)) = 0.078125 _Parallax ("Height", Range (0.005, 0.08)) = 0.02 _MainTex ("Base (RGB) TransGloss (A)", 2D) = "white" {} _BumpMap ("Normalmap", 2D) = "bump" {} _ParallaxMap ("Heightmap (A)", 2D) = "black" {} } SubShader { Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"} LOD 600 CGPROGRAM #pragma surface surf BlinnPhong alpha #pragma exclude_renderers flash sampler2D _MainTex; sampler2D _BumpMap; sampler2D _ParallaxMap; fixed4 _Color; half _Shininess; float _Parallax; struct Input { float2 uv_MainTex; float2 uv_BumpMap; float3 viewDir; }; void surf (Input IN, inout SurfaceOutput o) { half h = tex2D (_ParallaxMap, IN.uv_BumpMap).w; float2 offset = ParallaxOffset (h, _Parallax, IN.viewDir); IN.uv_MainTex += offset; IN.uv_BumpMap += offset; fixed4 tex = tex2D(_MainTex, IN.uv_MainTex); o.Albedo = tex.rgb * _Color.rgb; o.Gloss = tex.a; o.Alpha = tex.a * _Color.a; o.Specular = _Shininess; o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap)); } ENDCG } FallBack "Transparent/Bumped Specular" }

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• Rotate an image in a scaled context

  - by nathan

  Here is my working piece of code to rotate an image toward a point (in my case, the mouse cursor). float dx = newx - ploc.x; float dy = newy - ploc.y; float angle = (float) Math.toDegrees(Math.atan2(dy, dx)); Where ploc is the location of the image i'm rotating. And here is the rendering code: g.rotate(loc.x + width / 2, loc.y + height / 2, angle); g.drawImage(frame, loc.x, loc.y); Where loc is the location of the image and "width" and "height" are respectively the width and height of the image. What changes are needed to make it works on a scaled context? e.g make it works with something like g.scale(sx, sy).

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• How to I access "Deny" message from a Lidgren client?

  - by TJ Mott

  I'm using the Lidgren v3 network for a UDP client/server networking model. On the server end, I'm initializing a NetServer object with the NetIncomingMessage.ConnectionApproval message type enabled. So the client is able to successfully connect and the first packet it sends is a login packet, containing a username and password supplied by the user. The server is receiving that and doing some black magic to authenticate, and everything works up to that point. If the login fails, the server calling NetIncomingMessage.SenderConnection.Deny("Invalid Login Credentials"). I want to know how to properly receive this deny message on the client. I'm getting the message, it shows up with a message type of NetIncomingMessage.StatusChanged. If I call ReadString on that message, I get a corrupted version of the string I passed to the Deny method on the server. The type of corruption varies, I've seen odd characters in there but in every case it's truncated and is way shorter than the string I entered. Any ideas? The official documentation is sparse on this topic. I could use pointers from anyone who has successfully used the Lidgren library and uses the Accept or Deny methods. Also, if I don't do any authentication and just Approve() the connection every time, stuff actually works just fine and I'm getting reliable two-way UDP traffic. (And lastly, Stack Exchange said I don't have enough reputation to use the "Lidgren" tag....???)

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• Generating geometry when using VBO

  - by onedayitwillmake

  Currently I am working on a project in which I generate geometry based on the players movement. A glorified very long trail, composed of quads. I am doing this by storing a STD::Vector, and removing the oldest verticies once enough exist, and then calling glDrawArrays. I am interested in switching to a shader based model, usually examples I see the VBO is generated at start and then that's basically it. What is the best route to go about creating geometry in real time, using shader / VBO approach

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• x axis detection issues platformer starter kit

  - by dbomb101

  I've come across a problem with the collision detection code in the platformer starter kit for xna.It will send up the impassible flag on the x axis despite being nowhere near a wall in either direction on the x axis, could someone could tell me why this happens ? Here is the collision method. /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, TileCollision collision = Level.GetCollision(x, y); if (collision != TileCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == TileCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == TileCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } //This is the section which deals with collision on the x-axis else if (collision == TileCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; }

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• How to move Objects smoothly like swimming arround

  - by philipp

  I have a Box2D project that is about to create a view where the user looks from the Sky onto Water. Or perhaps on a bathtub filled with water or something like this. The Object which holds the fluid actually does not matter, what matters is the movement of the bodies, because they should move like drops of grease on a soup, or wood on water, I can even imagine the the fluid is mercurial, extreme heavy and "lazy". How can I manipulate the bodies (every frame or time by time) to make them move like this? I started with randomly manipulation their linear velocity, but I turned out that this not very smooth and looks quite hard. Is it a better idea to check their velocity and apply impulses? Is there any example? Greetings philipp

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• OpenGL and gluUnProject, 3d object following mouse

  - by Robert

  i have a 3d object and i want him to "follow" my mouse position, so i use gluUnProject function to convert screen coordinates to 3d world coordinates and i translate this object with the new coordinates. Its working but i have a problem, my object can follow my mouse but he is moving extremely fast, when i move my mouse a little bit(something like 2 pixels), its moving extremly fast in the 3d world. I want something like that : http://www.youtube.com/watch?v=90zS8SVUAIY (red circle following mouse). Thanks for your help.

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• How to draw a global day night curve

  - by Lumis

  I see many applications which have world-clock map, and I would like to make my own to enhance some of my mobile apps. I wonder if anybody has any knowledge where to start, how to draw a curved shadow representing the dawn and the sunset on the globe. See the example: http://aa.usno.navy.mil/imagery/earth/map?year=2012&month=6&day=19&hour=14&minute=47 I think that this curve goes up and down and creates an artic day/night etc Perhaps there is some acceptable approximation formula without a need to load data for each our and each global parallel and meridian...

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• Translating an Object to a certain Vector 3 in OpenGL and Java LWJGL

  - by aliasmk

  So after almost two hours, I got the hang of using glTranslated() (with Java and LWJGL). If I am correct, applying glTranslated on an object moves that object with the x,y,z relative to the previously moved object. I believe the correct term for this is local vs global, global being the one I want. I was wondering if there was a way to translate an object to a specific XYZ position, or relative to the origin. Thanks! (Code or other details can be supplied if it helps, just let me know. Also sorry if this is a noob comment, Im very new to OpenGL.)

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• Checking is sides of cubes are solid

  - by Christian Frantz

  In relation to this question: http://gamedev.stackexchange.com/a/28524/31664 And a question I asked earlier: Creating a DrawableGameComponent And also because my internet is too slow to get on chat. I'm wondering how to check if the sides of a cube are solid. I've created 12 methods, each one creating indices and vertices for sides of a cube. Now when I use these methods, the cube creates how it should. All 6 sides show up and its like I didnt change a thing. How can use if statements to check if the side of a cube is solid? The pseudocode from the question above shows this: if(!isSolidAt(x+1,y,z)) verticesToDraw += AddXPlusFace(x,y,z) But in my case is would be: if(!sideIsSolid) SetUpFrontFaceIndices(); My method simply takes these index and vertex values and adds them to a list indicesToDraw and verticesToDraw, as shown in the answer above

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• Mesh with quads to triangle mesh

  - by scape

  I want to use Blender for making models yet realize some of the polygons are not triangles but contain quads or more (example: cylinder top and bottom). I could export the the mesh as a basic mesh file and import it in to an openGL application and workout rendering the quads as tris, but anything with more than 4 vert indices is beyond me. Is it typical to convert the mesh to a triangle-based mesh inside blender before exporting it? I actually tried this through the quads_convert_to_tris method within a blender py script and the top of the cylinder does not look symmetrical. What is typically done to render a loaded mesh as a tri?

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• How is this lighting effect done?

  - by Mike

  This is the most beautiful 2d lighting I have ever seen. Does anyone know how he went about doing it? http://www.youtube.com/watch?v=BIQRhOFkvQY http://www.youtube.com/watch?v=tnTYXPuecMs http://www.youtube.com/watch?v=rhC_jVM8IYU http://www.youtube.com/watch?v=_Aw5BdjWqqU Or download it here: http://grantkot.com/PollutedPlanet/publish.htm edit: I am not asking how the particles are simulated; I don't care about the physics.

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• Retrieving model position after applying modeltransforms in XNA

  - by Glen Dekker

  For this method that the goingBeyond XNA tutorial provides, it would be really convenient if I could retrieve the new position of the model after I apply all the transforms to the mesh. I have edited the method a little for what I need. Does anyone know a way I can do this? public void DrawModel( Camera camera ) { Matrix scaleY = Matrix.CreateScale(new Vector3(1, 2, 1)); Matrix temp = Matrix.CreateScale(100f) * scaleY * rotationMatrix * translationMatrix * Matrix.CreateRotationY(MathHelper.Pi / 6) * translationMatrix2; Matrix[] modelTransforms = new Matrix[model.Bones.Count]; model.CopyAbsoluteBoneTransformsTo(modelTransforms); if (camera.getDistanceFromPlayer(position+position1) > 3000) return; foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.World = modelTransforms[mesh.ParentBone.Index] * temp * worldMatrix; effect.View = camera.viewMatrix; effect.Projection = camera.projectionMatrix; } mesh.Draw(); } }

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• Toon/cel shading with variable line width?

  - by Nick Wiggill

  I see a few broad approaches out there to doing cel shading: Duplication & enlargement of model with flipped normals (not an option for me) Sobel filter / fragment shader approaches to edge detection Stencil buffer approaches to edge detection Geometry (or vertex) shader approaches that calculate face and edge normals Am I correct in assuming the geometry-centric approach gives the greatest amount of control over lighting and line thickness, as well eg. for terrain where you might see the silhouette line of a hill merging gradually into a plain? What if I didn't need pixel lighting on my terrain surfaces? (And I probably won't as I plan to use cell-based vertex- or texturemap-based lighting/shadowing.) Would I then be better off sticking with the geometry-type approach, or go for a screen space / fragment approach instead to keep things simpler? If so, how would I get the "inking" of hills within the mesh silhouette, rather than only the outline of the entire mesh (with no "ink" details inside that outline? Lastly, is it possible to cheaply emulate the flipped-normals approach, using a geometry shader? Is that exactly what the GS approaches do? What I want - varying line thickness with intrusive lines inside the silhouette... What I don't want...

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• Triangle Strips and Tangent Space Normal Mapping

  - by Koarl

  Short: Do triangle strips and Tangent Space Normal mapping go together? According to quite a lot of tutorials on bump mapping, it seems common practice to derive tangent space matrices in a vertex program and transform the light direction vector(s) to tangent space and then pass them on to a fragment program. However, if one was using triangle strips or index buffers, it is a given that the vertex buffer contains vertices that sit at border edges and would thus require more than one normal to derive tangent space matrices to interpolate between in fragment programs. Is there any reasonable way to not have duplicate vertices in your buffer and still use tangent space normal mapping? Which one do you think is better: Having normal and tangent encoded in the assets and just optimize the geometry handling to alleviate the cost of duplicate vertices or using triangle strips and computing normals/tangents completely at run time? Thinking about it, the more reasonable answer seems to be the first one, but why might my professor still be fussing about triangle strips when it seems so obvious?

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• Illumination and Shading for computer graphics class

  - by Sam I Am

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

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• What is wrong with my specular phong shading

  - by Thijser

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

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