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  • Suitability of ground fog using layered alpha quads?

    - by Nick Wiggill
    A layered approach would use a series of massive alpha-textured quads arranged parallel to the ground, intersecting all intervening terrain geometry, to provide the illusion of ground fog quite effectively from high up, looking down, and somewhat less effectively when inside the fog and looking toward the horizon (see image below). Alternatively, a shader-heavy approach would instead calculate density as function of view distance into the ground fog substrate, and output the fragment value based on that. Without having to performance-test each approach myself, I would like first to hear others' experiences (not speculation!) on what sort of performance impact the layered alpha texture approach is likely to have. I ask specifically due to the oft-cited impacts of overdraw (not sure how fill-rate bound your average desktop system is). A list of games using this approach, particularly older games, would be immensely useful: if this was viable on pre DX9/OpenGL2 hardware, it is likely to work fine for me. One big question is in regards to this sort of effect: (Image credit goes to Lume of lume.com) Notice how the vertical fog gradation is continuous / smooth. OTOH, using textured quad layers, I can only assume that layers would be mighty obvious when walking through them -- the more sparse they were, the more obvious this would be. This is in contrast to where fog planes are aligned to face the player every frame, where this coarseness would be much less obvious.

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  • Collision detection of convex shapes on voxel terrain

    - by Dave
    I have some standard convex shapes (cubes, capsules) on a voxel terrain. It is very easy to detect single vertex collisions. However, it becomes computationally expensive when many vertices are involved. To clarify, currently my algorithm represents a cube as multiple vertices covering every face of the cube, not just the corners. This is because the cubes can be much bigger than the voxels, so multiple sample points (vertices) are required (the distance between sample points must be at least the width of a voxel). This very rapidly becomes intractable. It would be great if there were some standard algorithm(s) for collision detection between convex shapes and arbitrary voxel based terrain (like there is with OBB's and seperating axis theorem etc). Any help much appreciated.

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  • Any reliable polygon normal calculation code?

    - by Jenko
    Do you have any reliable face normal calculation code? I'm using this but it fails when faces are 90 degrees upright or similar. // the normal point var x:Number = 0; var y:Number = 0; var z:Number = 0; // if is a triangle with 3 points if (points.length == 3) { // read vertices of triangle var Ax:Number, Bx:Number, Cx:Number; var Ay:Number, By:Number, Cy:Number; var Az:Number, Bz:Number, Cz:Number; Ax = points[0].x; Bx = points[1].x; Cx = points[2].x; Ay = points[0].y; By = points[1].y; Cy = points[2].y; Az = points[0].z; Bz = points[1].z; Cz = points[2].z; // calculate normal of a triangle x = (By - Ay) * (Cz - Az) - (Bz - Az) * (Cy - Ay); y = (Bz - Az) * (Cx - Ax) - (Bx - Ax) * (Cz - Az); z = (Bx - Ax) * (Cy - Ay) - (By - Ay) * (Cx - Ax); // if is a polygon with 4+ points }else if (points.length > 3){ // calculate normal of a polygon using all points var n:int = points.length; x = 0; y = 0; z = 0 // ensure all points above 0 var minx:Number = 0, miny:Number = 0, minz:Number = 0; for (var p:int = 0, pl:int = points.length; p < pl; p++) { var po:_Point3D = points[p] = points[p].clone(); if (po.x < minx) { minx = po.x; } if (po.y < miny) { miny = po.y; } if (po.z < minz) { minz = po.z; } } if (minx > 0 || miny > 0 || minz > 0){ for (p = 0; p < pl; p++) { po = points[p]; po.x -= minx; po.y -= miny; po.z -= minz; } } var cur:int = 1, prev:int = 0, next:int = 2; for (var i:int = 1; i <= n; i++) { // using Newell method x += points[cur].y * (points[next].z - points[prev].z); y += points[cur].z * (points[next].x - points[prev].x); z += points[cur].x * (points[next].y - points[prev].y); cur = (cur+1) % n; next = (next+1) % n; prev = (prev+1) % n; } } // length of the normal var length:Number = Math.sqrt(x * x + y * y + z * z); // if area is 0 if (length == 0) { return null; }else{ // turn large values into a unit vector x = x / length; y = y / length; z = z / length; }

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  • How to create a fountain in UDK

    - by user36425
    I'm trying to make a fountain in my level in UDK, I made the base of the fountain by using a Cylinder build and now I'm trying to put water in it. I went to use the fluidSurfaceActor but I notice that this is square but my fountain is a cylinder. Is there a way that I can change the shape of the fluidSurfaceActor to fit the builder brush shape or is there another way to do this? Or is it hopeless and I have to make my fountain into a cube? Here is a link/picture to the screenprint of what I'm talking about:

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  • How do you turn a cube into a sphere?

    - by Tom Dalling
    I'm trying to make a quad sphere based on an article, which shows results like this: I can generate a cube correctly: But when I convert all the points according to this formula (from the page linked above): x = x * sqrtf(1.0 - (y*y/2.0) - (z*z/2.0) + (y*y*z*z/3.0)); y = y * sqrtf(1.0 - (z*z/2.0) - (x*x/2.0) + (z*z*x*x/3.0)); z = z * sqrtf(1.0 - (x*x/2.0) - (y*y/2.0) + (x*x*y*y/3.0)); My sphere looks like this: As you can see, the edges of the cube still poke out too far. The cube ranges from -1 to +1 on all axes, like the article says. Any ideas what is wrong?

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  • Calculate an AABB for bone animated model

    - by Byte56
    I have a model that has its initial bounding box calculated by finding the maximum and minimum on the x, y and z axes. Producing a correct result like so: The vertices are then stored in a VBO and only altered with matrices for rotation and bone animation. Currently the bounds are not updated when the model is altered. So the animated and rotated model has bounds like so: (Maybe it's hard to tell, but the bounds are the same as before, and don't accurately represent the rotated/animated model) So my question is, how can I calculate the bounding box using the armature matrices and rotation/translation matrices for each model? Keep in mind the modified vertex data is not available because those calculations are performed on the GPU in the shader. The end result I want is to have an accurate AABB the represents the animated model for picking/basic collision checks.

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  • OpenGL: Want to keep gun on top of car and be able to control angle. Having difficulties.

    - by Blair
    So I am making a simple game. I want to put a gun on top of a car so basically like a long rod in the middle of a black is how I am modelling it right now. I want to be able to control the angle of the gun. Basically it can go forward all the way so that it is parallel to the ground facing the direction the car is moving or it can point behind the car and any of the angles in between these positions. I have something like the following right now but its not really working. Is there an better way to do this that I am not seeing? #This will place the car glPushMatrix() glTranslatef(self.position.x,1.5,self.position.z) glRotated(self.rotation, 0.0, 1.0, 0.0) glScaled(0.5, 0.5, 0.5) glCallList(self.model.gl_list) glPopMatrix() #This will place the gun on top glPushMatrix() glTranslatef(self.position.x,2.5,self.position.z) glRotated(self.tube_angle, self.direction.z, 0.0, self.direction.x) print self.direction.z glRotated(45, self.position.z, 0.0, self.position.x) glScaled(1.0, 0.5, 1.0) glCallList(self.tube.gl_list) glPopMatrix() This almost works. It moves the gun up and down. But when the car moves around the angle of the gun changes. Not what I want.

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  • What's a good data structure solution for a scene manager in XNA?

    - by tunnuz
    Hello, I'm playing with XNA for a game project of myself, I had previous exposure to OpenGL and worked a bit with Ogre, so I'm trying to get the same concepts working on XNA. Specifically I'm trying to add to XNA a scene manager to handle hierarchical transforms, frustum (maybe even occlusion) culling and transparency object sorting. My plan was to build a tree scene manager to handle hierarchical transforms and lighting, and then use an Octree for frustum culling and object sorting. The problem is how to do geometry sorting to support transparencies correctly. I know that sorting is very expensive if done on a per-polygon basis, so expensive that it is not even managed by Ogre. But still images from Ogre look right. Any ideas on how to do it and which data structures to use and their capabilities? I know people around is using: Octrees Kd-trees (someone on GameDev forum said that these are far better than Octrees) BSP (which should handle per-polygon ordering but are very expensive) BVH (but just for frustum and occlusion culling) Thank you Tunnuz

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  • Java game object pool management

    - by Kenneth Bray
    Currently I am using arrays to handle all of my game objects in the game I am making, and I know how terrible this is for performance. My question is what is the best way to handle game objects and not hurt performance? Here is how I am creating an array and then looping through it to update the objects in the array: public static ArrayList<VboCube> game_objects = new ArrayList<VboCube>(); /* add objects to the game */ while (!Display.isCloseRequested() && !Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) { for (int i = 0; i < game_objects.size(); i++){ // draw the object game_objects.get(i).Draw(); game_objects.get(i).Update(); //world.updatePhysics(); } } I am not looking for someone to write me code for asset or object management, just point me into a better direction to get better performance. I appreciate the help you guys have provided me in the past, and I dont think I would be as far along with my project without the support on stack exchange!

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  • Asset missing problem XNA

    - by ChocoMan
    I'm using VS2010 with XNA 4.0 and I'm trying to load an FBX model with texture on the screen. The problem I'm having is this error: Missing Asset: C:\Users\ChocoMan\Documents\Visual Studio 2010\Projects\XNAGame\Documents\Visual Studio\Projects\XNAGame\XNAGameContent\Textures\texture.bmp but the actual path to the texture is C:\Users\ChocoMan\Documents\Visual Studio\Projects\XNAGame\XNAGameContent\Textures\texture.bmp Also, when I linked the texture in Maya, I used the above address. Does anyone know why VS is looking for an incorrect address that doesnt exist?

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  • Any reliable polygon normal calculation code?

    - by Jenko
    I'm currently calculating the normal vector of a polygon using this code, but for some faces here and there it calculates a wrong normal. I don't really know what's going on or where it fails but its not reliable. Do you have any polygon normal calculation that's tested and found to be reliable? // calculate normal of a polygon using all points var n:int = points.length; var x:Number = 0; var y:Number = 0; var z:Number = 0 // ensure all points above 0 var minx:Number = 0, miny:Number = 0, minz:Number = 0; for (var p:int = 0, pl:int = points.length; p < pl; p++) { var po:_Point3D = points[p] = points[p].clone(); if (po.x < minx) { minx = po.x; } if (po.y < miny) { miny = po.y; } if (po.z < minz) { minz = po.z; } } for (p = 0; p < pl; p++) { po = points[p]; po.x -= minx; po.y -= miny; po.z -= minz; } var cur:int = 1, prev:int = 0, next:int = 2; for (var i:int = 1; i <= n; i++) { // using Newell method x += points[cur].y * (points[next].z - points[prev].z); y += points[cur].z * (points[next].x - points[prev].x); z += points[cur].x * (points[next].y - points[prev].y); cur = (cur+1) % n; next = (next+1) % n; prev = (prev+1) % n; } // length of the normal var length:Number = Math.sqrt(x * x + y * y + z * z); // turn large values into a unit vector if (length != 0){ x = x / length; y = y / length; z = z / length; }else { throw new Error("Cannot calculate normal since triangle has an area of 0"); }

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  • Physics timestep questions

    - by SSL
    I've got a projectile working perfectly using the code below: //initialised in loading screen 60 is the FPS - projectilEposition and velocity are Vector3 types gravity = new Vector3(0, -(float)9.81 / 60, 0); //called every frame projectilePosition += projectileVelocity; This seems to work fine but I've noticed in various projectile examples I've seen that the elapsedtime per update is taken into account. What's the difference between the two and how can I convert the above to take into account the elapsedtime? (I'm using XNA - do I use ElapsedTime.TotalSeconds or TotalMilliseconds)? Edit: Forgot to add my attempt at using elapsedtime, which seemed to break the physics: projectileVelocity.Y += -(float)((9.81 * gameTime.ElapsedGameTime.TotalSeconds * gameTime.ElapsedGameTime.TotalSeconds) * 0.5f); Thanks for the help

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  • How to get Autocad working with Wine?

    - by gabriel
    I am trying 3 years now installing Autocad,*3ds Max* and Revit architecture on Ubuntu with wine! Every year I am very optimistic 'cause I see the new wine versions already improved. So, now I am starting again in a clean Ubuntu installation to install Autocad 2013 with wine 1.4. I am not trying to have an answer only for me, but I want this community to try and finally we can achieve that! The winetricks have already net framework 4 to install which is the reason I have not already ran to the past Autocad. So, I would like to remove completely my windows 7 partition from my pc and go on a linux machine without loosing the powerfull architectural programms.I know all about Blender and staff so I just want you to help find a solution on that, because I know there is a solution! Maybe I will have to learn all the c++ or python etc. But I am sure that a solution can come with the help of all of us! Any suggestion about this problem will be very nice and helpfull.

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  • Terrain sqaure loading

    - by AndroidXTr3meN
    Games like Skyrim, Morrowind, and more are using quads or sqaure to divide the terrain if im correct. The player is always at #5 1 | 2 | 3 4 | 5 | 6 7 | 8 | 9 So whenever you cross the border you unload and load the new "areas" But if the user goes just over the edge and then the second after goes back previous area a lot of uneccessary loading and unloading is done. Is there a general approach to this becuase I dont think games like skyrim have this issue? Cheers!

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  • Vertex Array Object (OpenGL)

    - by Shin
    I've just started out with OpenGL I still haven't really understood what Vertex Array Objects are and how they can be employed. If Vertex Buffer Object are used to store vertex data (such as their positions and texture coordinates) and the VAOs only contain status flags, where can they be used? What's their purpose? As far as I understood from the (very incomplete and unclear) GL Wiki, VAOs are used to set the flags/status for every vertex, following the order described in the Element Array Buffer, but the wiki was really ambiguous about it and I'm not really sure about what VAOs really do and how I could employ them.

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  • D3D11 how to simulate multiple depth channels

    - by Nock
    Here's what I'd like to achieve: Rendering a first pass of objects in my scene, using standard depth comparison Rendering another pass of objects in the same scene, but with the following rules: A Pixel of the 2nd pass always override the first pass (no depth compare between them) Use Depth comparison between pixels written from the second pass. In English I want depth comparison made inside each pass but I always want the second pass pixels to override the first pass ones. Some things I've thought: I tried to think about using stencil to solve this, but I couldn't find a way. I know I could render into a separate target the second pass then composite the result into the first, but I'd like to avoid that. I could use two separate Depth Buffer, one dedicated to each pass. (I never tried, but I figure it's possible to switch the depth buffer in a Render Target "on the fly") Any idea of the best solution? Thanks

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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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  • 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 is the proper way to maintain the angle of a gun mounted on a car?

    - by Blair
    So I am making a simple game. I want to put a gun on top of a car. I want to be able to control the angle of the gun. Basically it can go forward all the way so that it is parallel to the ground facing the direction the car is moving or it can point behind the car and any of the angles in between these positions. I have something like the following right now but its not really working. Is there an better way to do this that I am not seeing? #This will place the car glPushMatrix() glTranslatef(self.position.x,1.5,self.position.z) glRotated(self.rotation, 0.0, 1.0, 0.0) glScaled(0.5, 0.5, 0.5) glCallList(self.model.gl_list) glPopMatrix() #This will place the gun on top glPushMatrix() glTranslatef(self.position.x,2.5,self.position.z) glRotated(self.tube_angle, self.direction.z, 0.0, self.direction.x) print self.direction.z glRotated(45, self.position.z, 0.0, self.position.x) glScaled(1.0, 0.5, 1.0) glCallList(self.tube.gl_list) glPopMatrix() This almost works. It moves the gun up and down. But when the car moves around, the angle of the gun changes. Not what I want.

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  • How do I have to take into account the direction in which the camera is facing when creating a first person strafe (left/right) movement

    - by Chris
    This is the code I am currently using, and it works great, except for the strafe always causes the camera to move along the X axis which is not relative to the direction in which the camera is actually facing. As you can see currently only the x location is updated: [delta * -1, 0, 0] How should I take into account the direction in which the camera is facing (I have the camera's target x,y,z) when creating a first person strafe (left/right) movement? case 'a': var eyeOriginal = g_eye; var targetOriginal = g_target; var viewEye = g_math.subVector(g_eye, g_target); var viewTarget = g_math.subVector(g_target, g_eye); viewEye = g_math.addVector([delta * -1, 0, 0], viewEye); viewTarget = g_math.addVector([delta * -1, 0, 0], viewTarget); g_eye = g_math.addVector(viewEye, targetOriginal); g_target = g_math.addVector(viewTarget, eyeOriginal); break; case 'd': var eyeOriginal = g_eye; var targetOriginal = g_target; var viewEye = g_math.subVector(g_eye, g_target); var viewTarget = g_math.subVector(g_target, g_eye); viewEye = g_math.addVector([delta, 0, 0], viewEye); viewTarget = g_math.addVector([delta, 0, 0], viewTarget); g_eye = g_math.addVector(viewEye, targetOriginal); g_target = g_math.addVector(viewTarget, eyeOriginal); break;

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  • I want to learn the basics of Game Development [on hold]

    - by Mary
    I have programming experience and I would like to know how to start building games. I'm interested in building games for desktops and Android tablets. Could you list the general steps of Game Building? From the more common programming languages used to the software and frameworks available at each stage? I'm just trying to get the big picture of all the different options and tools I have at my disposal. Please leave some book recommendations and useful links!

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  • Scanline filling of polygons that share edges and vertices

    - by Belgin
    In this picture (a perspective projection of an icosahedron), the scanline (red) intersects that vertex at the top. In an icosahedron each edge belongs to two triangles. From edge a, only one triangle is visible, the other one is in the back. Same for edge d. Also, in order to determine what color the current pixel should be, each polygon has a flag which can either be 'in' or 'out', depending upon where on the scanline we currently are. Flags are flipped according to the intersection of the scanline with the edges. Now, as we go from a to d (because all edges are intersected with the scanline at that vertex), this happens: the triangle behind triangle 1 and triangle 1 itself are set 'in', then 2 is set in and 1 is 'out', then 3 is set 'in', 2 is 'out' and finally 3 is 'out' and the one behind it is set 'in', which is not the desired behavior because we only need the triangles which are facing us to be set 'in', the rest should be 'out'. How do process the edges in the Active Edge List (a list of edges that are currently intersected by the scanline) so the right polys are set 'in'? Also, I should mention that the edges are unique, which means there exists an array of edges in the data structure of the icosahedron which are pointed to by edge pointers in each of the triangles.

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  • What is the best way to check if there is overlap between player and static, non-collidable items in bullet physic engine

    - by tigrou
    I'd like to add non collidable objects (eg: power ups, items, ...) in a game world using Bullet Physics Engine and to know if there is collision between player and them. Some info : there is a lot of items ( 1000), all are box shapes and they don't overlap. Here is things i have tried : btDbvt* bvtItems = new btDbvt(); //btDbvt is a hierachical AABB tree, used by Bullet foreach(var item ...) { btDbvtVolume volume = ... //compute item AABB; bvtItems->insert(volume, (void*)someExtraData); } Then, to find collisions between items and player : playerRigidBody->getAabb(min, max); btDbvtVolume playervolume = ... //compute player AABB bvtItems->collideTV(bvtItems->m_root, playervolume, *someCollisionHandler); This works fairly well (and its very fast), however, there is a problem : it only check items AABB against player AABB. That loss of precision is acceptable for items but not for player which is not a box. It would actually need another check to make sure player really collide with item but i don't know how to do this in Bullet. It would have been nice to have a function like this : playerRigidBody->checkCollisionWithAABB(); After doing trying that, I discovered that a btGhostObject exist and seems to have been made for that. I changed my code like this : foreach(var item...) { btCollisionObject* ghostObject = new btGhostObject(); ghostObject->setCollisionShape(boxShape); ghostObject->setCollisionFlags(ghostObject->getCollisionFlags() | btCollisionObject::CF_NO_CONTACT_RESPONSE); startTransform.setOrigin(...); //item position ghostObject->setWorldTransform(startTransform); dynamicsWorld->addCollisionObject(ghostObject, btBroadphaseProxy::SensorTrigger, btBroadphaseProxy:: CharacterFilter); } It also works ok, but there is a huge fps drop (almost ten times slower) which is not acceptable. Maybe there is something missing (forget set a flag) and Bullet is doing extra job for nothing or maybe all that ghostObjects are polluting broad phase and ghostObject is not the right thing for that. Any help would be appreciated.

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  • Arbitrary projection matrix from 6 arbitrary frustum planes

    - by Doub
    A projection matrix represent a tranformation from the camera view space to the rendering system clip space. In other words, it defines the transormation between a 6-sided frustum to the clip cube. The glOrtho and glFrustum use only 6 parameter to define such a projection, but impose several constraints on the frustum that will get projected to the clip cube: the near and far planes are parallel, the left and right planes intersect on a vertical line, and the top and bottom planes intersect on a horizontal lines, both lines being parallel to the near and far planes. I'd like to lift these restrictions. So, from the definition of the 6 frustum side planes (in whatever representation you see fit), how can I compute a general projection matrix?

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  • Calculating a child Position, Rotation and Scale values?

    - by Sergio Plascencia
    I am making my own game editor(just for fun) anyway I have problem that I had several days trying to resolve but I have been unsuccessful. Here goes... I have an object "A": Position: (3,3,3), Rotation: (45,10,0), Scale(1,2,2.5) And an object "B": Position: (1,1,1), Rotation: (10,34,18), Scale(1.5,2,1) I now make a parent/child relationship. "B" is a child of "A": A |--B When I do the relationship I need to re-calculate the Child("B") Position, Rotation and Scale such that it maintains its current position, rotation and scale(Location in world). So for child position "B" it would now be (-2, -2, -2) since now "A" it is center and (-2, -2, -2) will keep the object in its same position. I think I got the Position and scale figure out, but rotation I cant. So I was trying to figure out what to do and what I did is opened Unity and run the same example and I did noticed that when making an abject a child object the child object did not moved at all but had its Position, Rotation and Scale values changed(Related to the parent). For example: Unity (Parent Object "A"): Position: (0,0,0) Rotation: (45,10,0) Scale: (1,1,1) Unity (Child Object "B"): Position: (0,0,0) Rotation: (0,0,0) Scale: (1,1,1) When making it a parent child relation("B" is a child of "A") the child object("B") in its Rotation values now has: X: -44.13605 Y: -14.00195 Z: 9.851074 If I plug the same values to my editor(To the child "B" rotation X, Y, Z values) the object does not move at all. So I basically need to know how did Unity arrive at those rotation values for the child(What are the calculations?). If you can help and put all the equations for the Position, Rotation or Scale then I can double check I am doing it correctly but with the Rotation I really need help. Thanks!

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