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• how to add water effect to an image

  - by brainydexter

  This is what I am trying to achieve: A given image would occupy say 3/4th height of the screen. The remaining 1/4th area would be a reflection of it with some waves (water effect) on it. I'm not sure how to do this. But here's my approach: render the given texture to another texture called mirror texture (maybe FBOs can help me?) invert mirror texture (scale it by -1 along Y) render mirror texture at height = 3/4 of the screen add some sense of noise to it OR using pixel shader and time, put pixel.z = sin(time) to make it wavy (Tech: C++/OpenGL/glsl) Is my approach correct ? Is there a better way to do this ? Also, can someone please recommend me if using FrameBuffer Objects would be the right thing here ? Thanks

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• Getting the number of fragments which passed the depth test

  - by Etan

  In "modern" environments, the "NV Occlusion Query" extension provides a method to get the number of fragments which passed the depth test. However, on the iPad / iPhone using OpenGL ES, the extension is not available. What is the most performant approach to implement a similar behaviour in the fragment shader? Some of my ideas: Render the object completely in white, then count all the colors together using a two-pass shader where first a vertical line is rendered and for each fragment the shader computes the sum over the whole row. Then, a single vertex is rendered whose fragment sums all the partial sums of the first pass. Doesn't seem to be very efficient. Render the object completely in white over a black background. Downsample recursively, abusing the hardware linear interpolation between textures until being at a reasonably small resolution. This leads to fragments which have a greyscale level depending on the number of white pixels where in their corresponding region. Is this even accurate enough? Use mipmaps and simply read the pixel on the 1x1 level. Again the question of accuracy and if it is even possible using non-power-of-two textures. The problem wit these approaches is, that the pipeline gets stalled which results in major performance issues. Therefore, I'm looking for a more performant way to accomplish my goal. Using the EXT_OCCLUSION_QUERY_BOOLEAN extension Apple introduced EXT_OCCLUSION_QUERY_BOOLEAN in iOS 5.0 for iPad 2. "4.1.6 Occlusion Queries Occlusion queries use query objects to track the number of fragments or samples that pass the depth test. An occlusion query can be started and finished by calling BeginQueryEXT and EndQueryEXT, respectively, with a target of ANY_SAMPLES_PASSED_EXT or ANY_SAMPLES_PASSED_CONSERVATIVE_EXT. When an occlusion query is started with the target ANY_SAMPLES_PASSED_EXT, the samples-boolean state maintained by the GL is set to FALSE. While that occlusion query is active, the samples-boolean state is set to TRUE if any fragment or sample passes the depth test. When the occlusion query finishes, the samples-boolean state of FALSE or TRUE is written to the corresponding query object as the query result value, and the query result for that object is marked as available. If the target of the query is ANY_SAMPLES_PASSED_CONSERVATIVE_EXT, an implementation may choose to use a less precise version of the test which can additionally set the samples-boolean state to TRUE in some other implementation dependent cases." The first sentence hints on a behavior which is exactly what I'm looking for: getting the number of pixels which passed the depth test in an asynchronous manner without much performance loss. However, the rest of the document describes only how to get boolean results. Is it possible to exploit this extension to get the pixel count? Does the hardware support it so that there may be hidden API to get access to the pixel count? Other extensions which could be exploitable would be debugging features like the number of times the fragment shader was invoked (PSInvocations in DirectX - not sure if something simila is available in OpenGL ES). However, this would also result in a pipeline stall.

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• SDL2 with OpenGL -- weird results, what's wrong?

  - by ber4444

  I'm porting an app to iOS, and therefore need to upgrade it to SDL2 from SDL1.2 (so far I'm testing it as an on OS X desktop app only). However, when running the code with SDL2, I'm getting weird results as shown on the second image below (the first image is how it looks with SDL, correctly). The single changeset that causes this is this one, do you see something obviously wrong there, or does SDL2 have some OpenGL nuances I'm unaware of? My SDL is based on changeset dd7e57847ea9 from HG (since then there is one "Allow specifying of OpenGL 3.2 Core Profile on Mac OS X" commit, not sure if that would help).

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• Blender to 3ds max to cal3d format

  - by Kaliber64

  There are quite a few questions on cal3d but they are old and don't apply anymore. In Blender(must be 2.49a for python script to work!!!): I have a scene with 7 meshes, 1 armature, 10 bones. I tried going to one mesh to simplify it but doesn't change anything. I found a small blend file that was used for cal3d and it exported just fine. So I tried to copy it's setup with no success. EDIT*8/13/2012 In the last week here is what I have found so far. I made the mesh in the newest blender(2.62?) and exported it to import it in the old one(2.49a). Did an animation in the old one because importing new blend files to old blenders, its just said it would lose keyframe data and all was good. And then you get the last problem of it not exporting meshes. BUT I found that meshes made in the old one export regardless. I can't find any that won't export. So if I used the old blender to remake my model I could get it to export :) At this point I found a modified release of cal3d (because the most core model variable would not initiate as I made a really small test subject in old blender instead of remaking my big one which took 4 hours.) which fixes the morph objects and adds what cal3d left off with. Under their license they have to release the modification but it has no documentation so I have to figure it out on my own. Its mostly the same. But with this lib it came with a 3ds max exporter. My question now is how do I transfer armature and mesh information from blender to 3ds max in order to export into cal3d format. Every time I try the models are see through and small and there are no bones. The formats I have tried to import are .3ds .obj(mesh only) and COLLADA. In all of them the mesh is invisible and no bones. It says the default texture is on so I should be able to see it. All the vertices are present I found a vertex highlighter so I can see those. If any of this is confusing let me know so I can clear it up. Its late .<=sleep.

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• Finding direction of travel in a world with wrapped edges

  - by crazy

  I need to find the shortest distance direction from one point in my 2D world to another point where the edges are wrapped (like asteroids etc). I know how to find the shortest distance but am struggling to find which direction it's in. The shortest distance is given by: int rows = MapY; int cols = MapX; int d1 = abs(S.Y - T.Y); int d2 = abs(S.X - T.X); int dr = min(d1, rows-d1); int dc = min(d2, cols-d2); double dist = sqrt((double)(dr*dr + dc*dc)); Example of the world : : T : :--------------:--------- : : : S : : : : : : T : : : :--------------: In the diagram the edges are shown with : and -. I've shown a wrapped repeat of the world at the top right too. I want to find the direction in degrees from S to T. So the shortest distance is to the top right repeat of T. but how do I calculate the direction in degreed from S to the repeated T in the top right? I know the positions of both S and T but I suppose I need to find the position of the repeated T however there more than 1. The worlds coordinates system starts at 0,0 at the top left and 0 degrees for the direction could start at West. It seems like this shouldn’t be too hard but I haven’t been able to work out a solution. I hope somone can help? Any websites would be appreciated.

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• OpenGL sprites and point size limitation

  - by Srdan

  I'm developing a simple particle system that should be able to perform on mobile devices (iOS, Andorid). My plan was to use GL_POINT_SPRITE/GL_PROGRAM_POINT_SIZE method because of it's efficiency (GL_POINTS are enough), but after some experimenting, I found myself in a trouble. Sprite size is limited (to usually 64 pixels). I'm calculating size using this formula gl_PointSize = in_point_size * some_factor / distance_to_camera to make particle sizes proportional to distance to camera. But at some point, when camera is close enough, problem with size limitation emerges and whole system starts looking unrealistic. Is there a way to avoid this problem? If no, what's alternative? I was thinking of manually generating billboard quad for each particle. Now, I have some questions about that approach. I guess minimum geometry data would be four vertices per particle and index array to make quads from these vertices (with GL_TRIANGLE_STRIP). Additionally, for each vertex I need a color and texture coordinate. I would put all that in an interleaved vertex array. But as you can see, there is much redundancy. All vertices of same particle share same color value, and four texture coordinates are same for all particles. Because of how glDrawArrays/Elements works, I see no way to optimise this. Do you know of a better approach on how to organise per-particle data? Should I use buffers or vertex arrays, or there is no difference because each time I have to update all particles' data. About particles simulation... Where to do it? On CPU or on a vertex processors? Something tells me that mobile's CPU would do it faster than it's vertex unit (at least today in 2012 :). So, any advice on how to make a simple and efficient particle system without particle size limitation, for mobile device, would be appreciated. (animation of camera passing through particles should be realistic)

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• How to have operations with character/items in binary with concrete operations?

  - by Piperoman

  I have the next problem. A item can have a lot of states: NORMAL = 0000000 DRY = 0000001 HOT = 0000010 BURNING = 0000100 WET = 0001000 COLD = 0010000 FROZEN = 0100000 POISONED= 1000000 A item can have some states at same time but not all of them Is impossible to be dry and wet at same time. If you COLD a WET item, it turns into FROZEN. If you HOT a WET item, it turns into NORMAL A item can be BURNING and POISON Etc. I have tried to set binary flags to states, and use AND to combine different states, checking before if it is possible or not to do it, or change to another status. Does there exist a concrete approach to solve this problem efficiently without having an interminable switch that checks every state with every new state? It is relatively easy to check 2 different states, but if there exists a third state it is not trivial to do.

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• isometric background that covers the viewport [on hold]

  - by Richard

  The background image should cover the viewport. The technique I use now is a loop with an innerloop that draws diamond shaped images on a canvas element, but it looks like a rotated square. This is a nice example: ,that covers the whole viewport. I have heard something about clickthrough maps, but what more ways are there that are most efficient with mobile devices and javascript? Any advice in grid design out there?.

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• box2d resize bodies arround point

  - by philipp

  I have a compound object, consisting of a b2Body, vector-graphics and a list polygons which describe the b2body's shapes. This object has its own transformation matrix to centralize the storage of transformations. So far everything is working quiet fine, even scaling works, but not if i scale around a point. In the initialization phase of the object it is scaled around a point. This happens in this order: transform the main matrix transform the vector graphics and the polygons recreate the b2Body After this function ran, the shapes and all the graphics are exactly where they should be, BUT: after the first steps of the b2World the graphical stuff moves away from the body. When I ran the debugger I found out that the position of the body is 0/0 the red dot shows the center of scaling. the first image shows the basic setup and the second the final position of the graphics. This distance stays constant for the rest of the simulation. If I set the position via myBody.SetPosition( sx, sy ); the whole scenario just plays a bit more distant for the origin. Any Idea how to fix this? EDIT:: I came deeper down to the problem and it lies in the fact that i must not scale the transform matrix for the b2body shapes around the center, but set the b2body's position back to the point after scaling. But how can I calculate that point? EDIT 2 :: I came ever deeper down to it, even solved it, but this is a slow solution and i hope that there is somebody who understands what formula I need. assuming to have a set polygons relative to an origin as basis shapes for a b2body: scaling the whole object around a certain point is done in the following steps: i scale everything around the center except the polygons i create a clone of the polygons matrix i scale this clone around the point i calculate dx, dy as difference of clone.tx - original.tx and clone.ty - original.ty i scale the original polygon matrix NOT around the point i recreate the body i create the fixture i set the position of the body to dx and dy done! So what i an interested in is a formula for dx and dy without cloning matrices, scaling the clone around a point, getting dx and dy and finally scale the vertex matrix.

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• why is glVertexAttribDivisor crashing?

  - by 2am

  I am trying to render some trees with instancing. This is rather weird, but before sleeping yesterday night, I checked the code, and it was in a running state, when I got up this morning, it is crashing when I am calling glVertexAttribDivisor I haven't changed any code since yesterday. Here is how I am sending data to GPU for instancing. glGenBuffers(1, &iVBO); glBindBuffer(GL_ARRAY_BUFFER, iVBO); glBufferData(GL_ARRAY_BUFFER, (ml_instance->i_positions.size()*sizeof(glm::vec4)) , NULL, GL_STATIC_DRAW); glBufferSubData(GL_ARRAY_BUFFER, 0, (ml_instance->i_positions.size()*sizeof(glm::vec4)), &ml_instance->i_positions[0]); And then in vertex specification-- glBindBuffer(GL_ARRAY_BUFFER, iVBO); glVertexAttribPointer(i_positions, 4, GL_FLOAT, GL_FALSE, 0, 0); glEnableVertexAttribArray(i_positions); glVertexAttribDivisor(i_positions,1); // **THIS IS WHERE THE PROGRAM CRASHES** glDrawElementsInstanced(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0,TREES_INSTANCE_COUNT); I have checked ml_instance->i_positions, it has all the data that needs to render. I have checked the value of i_positions in vertex shader, it is the same as whatever I have defined there. I am little out of ideas here, everything looks pretty much fine. What am I missing?

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• How to derive euler angles from matrix or quaternion?

  - by KlashnikovKid

  Currently working on steering behavior for my AI and just hit a little mathematical bump. I'm in the process of writing an align function, which basically tries to match the agent's orientation with a target orientation. I've got a good source material for implementing this behavior but it uses euler angles to calculate the rotational delta, acceleration, and so on. This is nice, however I store orientation as a quaternion and the math library I'm using doesn't provide any functionality for deriving the euler angles. But if it helps I also have rotational matrices at my disposal too. What would be the best way to decompose the quaternion or rotational matrix to get the euler information? I found one source for decomposing the matrix, but I'm not quite getting the correct results. I'm thinking it may be a difference of column/row ordering of my matrices but then again, math isn't my strong point. http://nghiaho.com/?page_id=846

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• OpenGL Learning Material (that's up to date)

  - by Sauron

  So im sure there are topics on this, but alot of them list older material. And the last book: http://www.amazon.com/OpenGL-SuperBible-Comprehensive-Tutorial-Reference/dp/0321712617/ref=sr_1_1?ie=UTF8&qid=1346116133&sr=8-1&keywords=opengl REALLY REALLY disappointed me. I DO NOT want to use someone else's library to learn this stuff, that bothers me SOOO much. So I was hoping there was a newer book that goes into detail, and doesn't use some sort of library "Hiding" everything from you. Or should I just look at older material? If so....anything thats not "too" out of date. Terrain tutorials are a plus (that's kinda my "goal"). Thanks

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• Question about component based design: handling objects interaction

  - by Milo

  I'm not sure how exactly objects do things to other objects in a component based design. Say I have an Obj class. I do: Obj obj; obj.add(new Position()); obj.add(new Physics()); How could I then have another object not only move the ball but have those physics applied. I'm not looking for implementation details but rather abstractly how objects communicate. In an entity based design, you might just have: obj1.emitForceOn(obj2,5.0,0.0,0.0); Any article or explanation to get a better grasp on a component driven design and how to do basic things would be really helpful.

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• Error loading PCX image in FreeImage library

  - by khanhhh89

  I'm using FreeImage in C++ for loading texuture from the PCX image. My FreeImage code is as following: FREE_IMAGE_FORMAT fif = FIF_UNKNOWN; //pointer to the image data BYTE* bits(0); fif = FreeImage_GetFileType(m_fileName.c_str(), 0); if (FreeImage_FIFSupportsReading(fif)) dib = FreeImage_Load(fif, m_fileName.c_str()); //retrieve the image data bits = FreeImage_GetBits(dib); //get the image width and height width = FreeImage_GetWidth(dib); height = FreeImage_GetHeight(dib); My problem is the width and height variable are both 512, while the bits array is an empty string, which make the following OPENGL call corrupt: glTexImage2D(m_textureTarget, 0, GL_RGB, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, bits); While debugging, I notice that the "fif" variable (which contains the format of the image) is JPEG, while the Image is actually PCX. I wonder whether or not the FreeImage recognize the wrong format (from PCX to JPEG), so tha the bits array is an empty string. I hope to see your explanation about this problem. Thanks so much

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• Problem with DirectX scene-graph

  - by Alex

  I'm trying to implement a basic scene graph in DirectX using C++. I am using a left child-right sibling binary tree to do this. I'm having trouble updating each node's world transformation relative to its parent (and its parent's parent etc.). I'm struggling to get it to work recursively, though I can get it to work like this: for(int i = 0; i < NUM_OBJECTS; i++) { // Initialize to identity matrix. D3DXMatrixIdentity(&mObject[i].toWorldXForm); int k = i; while( k != -1 ) { mObject[i].toWorldXForm *= mObject[k].toParentXForm; k = mObject[k].parent; } } toWorldXForm is the object's world transform and toParentXForm is the object's transform relative to the parent. I want to do this using a method within my object class (the code above is in my main class). This is what I've tried but it doesn't work (only works with nodes 1 generation away from the root) if (this->sibling != NULL) this->sibling->update(toParentXForm); D3DXMatrixIdentity(&toWorldXForm); this->toWorldXForm *= this->toParentXForm; this->toWorldXForm *= toParentXForm; toParentXForm *= this->toParentXForm; if (this->child != NULL) this->child->update(toParentXForm); Sorry if I've not been clear, please tell me if there's anything else you need to know. I've no doubt it's merely a silly mistake on my part, hopefully an outside view will be able to spot the problem.

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• GLSL billboard move center of rotation

  - by Jacob Kofoed

  I have successfully set up a billboard shader that works, it can take in a quad and rotate it so it always points toward the screen. I am using this vertex-shader: void main(){ vec4 tmpPos = (MVP * bufferMatrix * vec4(0.0, 0.0, 0.0, 1.0)) + (MV * vec4( vertexPosition.x * 1.0 * bufferMatrix[0][0], vertexPosition.y * 1.0 * bufferMatrix[1][1], vertexPosition.z * 1.0 * bufferMatrix[2][2], 0.0) ); UV = UVOffset + vertexUV * UVScale; gl_Position = tmpPos; BufferMatrix is the model-matrix, it is an attribute to support Instance-drawing. The problem is best explained through pictures: This is the start position of the camera: And this is the position, looking in from 45 degree to the right: Obviously, as each character is it's own quad, the shader rotates each one around their own center towards the camera. What I in fact want is for them to rotate around a shared center, how would I do this? What I have been trying to do this far is: mat4 translation = mat4(1.0); translation = glm::translate(translation, vec3(pos)*1.f * 2.f); translation = glm::scale(translation, vec3(scale, 1.f)); translation = glm::translate(translation, vec3(anchorPoint - pos) / vec3(scale, 1.f)); Where the translation is the bufferMatrix sent to the shader. What I am trying to do is offset the center, but this might not be possible with a single matrix..? I am interested in a solution that doesn't require CPU calculations each frame, but rather set it up once and then let the shader do the billboard rotation. I realize there's many different solutions, like merging all the quads together, but I would first like to know if the approach with offsetting the center is possible. If it all seems a bit confusing, it's because I'm a little confused myself.

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• Where can I find free or buy "next-gen" 3D Assets?

  - by Valmond

  Usually I buy 3D Assets from sites like turbosquid.com or similar. My problem is that I have lately implemented glow, normal maps, specular (and specular power) maps and reflection maps and I can't find any models that use those techniques. So where can I find / buy "next gen" assets (at least models/items with a normal map)? I have checked for similar posts but those I found are about either free only or 2D or 'ordinary' 3D so I hope this is not a duplicate.

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• How do GameEngines stop Pixel Seams appearing in adjacent mesh boundaries due to FP imprecision?

  - by ufomorace

  Graphics cards are mathematically imprecise. So when some meshes are joined by their borders, the graphics card often makes mistakes and decides that some pixels at the seam represent neither object, and unwanted pixels appear. It's a natural behaviour on all graphics cards. How are such worries avoided in Pro Games? Batching? Shaders? Different tangent vectors? Merging? Overlaping seams? Dark backgrounds? Extra vertices at borders? Z precision? Camera distance tweaks? Screencap of a fix that ended up not working:

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• Impact of variable-length loops on GPU shaders

  - by Will

  Its popular to render procedural content inside the GPU e.g. in the demoscene (drawing a single quad to fill the screen and letting the GPU compute the pixels). Ray marching is popular: This means the GPU is executing some unknown number of loop iterations per pixel (although you can have an upper bound like maxIterations). How does having a variable-length loop affect shader performance? Imagine the simple ray-marching psuedocode: t = 0.f; while(t < maxDist) { p = rayStart + rayDir * t; d = DistanceFunc(p); t += d; if(d < epsilon) { ... emit p return; } } How are the various mainstream GPU families (Nvidia, ATI, PowerVR, Mali, Intel, etc) affected? Vertex shaders, but particularly fragment shaders? How can it be optimised?

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• Apply bone tranforms when importing FBX in XNA

  - by hichaeretaqua

  Preconditions: I have some models, that does only contain some meshes and one texture. There is no animation within the model. An example: a model of a table. I want to draw the Model with a custom effect, so I have to swap the effect after loading the model. In order to draw them correctly, I have to apply the bone transformation manually on each draw for each mesh and effect as can be seen here. So there are two questions: Is there a option during import that allows my to apply the bone transformation on all vertices, so that during draw call I should not have to do this? Is there a option during import that merges all vertices into a Vertex- and IndexBuffer, that allows me to draw the whole model with just one call? I'm pretty sure that the build-in "Autodesk FBX - XNA Framework" does not support this features, but maybe there is an other imported available or an other possibility I missed. The aim is to speed up rendering a little bit especially by using instancing. So having one VertexBuffer to draw at one time would be pretty nice.

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• Point[] and Tri not "could not be found"

  - by Craig Dannehl

  Hi I'm trying to learn how to load a .obj file using OpenTK in windows Forms. I have seen a lot of examples out there, but I do see almost everyone uses List, and Point[]. Code example show these highlighted like there IDE know what these are; for example List<Tri> tris = new List<Tri>(); but mine just returns "The type or namespace name 'Tri' could not be found" is there an include I need to add or a using I am missing. Currently have this using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Drawing; using OpenTK; using OpenTK.Graphics; using OpenTK.Graphics.OpenGL;

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• Blender: How to "meshify" an object I made from Bezier curves

  - by capcom

  I made a star shape using Bezier curves, and extruded it (see pic below): What I want to do is give it a rounder look - not just around the edges by using beveling. I want it to kind of look like this (well, that shape anyway): How would I go about doing this? Please keep in mind that I am extremely new to Blender. I thought that I could somehow turn this star into those default shapes that have tonnes of squares which I could pull out, and apply a mirror to it so that the same thing happens on both sides. I really don't know how to do it, and would appreciate your help.

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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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• Render full-screen gradient or texture

  - by Filip Skakun

  What's the simplest way to fill the background of the screen with a gradient or a texture in Direct3D 10/11? I'm building a Windows 8 metro app in which the camera never moves and I render some content in D3D, but I need to fill the background with something else than a solid color. Do I need to figure out the size and position of a rectangle and position it in 3D space or can I have some simpler solution? I don't care about depth at all, I don't use any depth buffer since all my content is sorted back to front, so I could just start by drawing to the background.

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• Is it normal to these Xcode prompts/errors when you deploy to IOS Simulator from Unity?

  - by Greg

  Just trying out the IOS build process.... Is it normal to see: Q1 - "upgrade to latest project format - project currently in Xcode 3.1 format, this will upgrade to 3.2" - just click OK and let Xcode do it's stuff? Q2 - same as Q1 but this time for the message "Remove obsolete build settings - will remove the build setting PREBINDING" Q3 - also when deploying to "Lastest IOS Simulator" you get the Simulator target produced, but also a non-simulator target which has lots of errors. So I assume you just ignore this target and not use it in Xcode correct? (i.e. just use the simulator target that is produced) Q4 - get a lot of warning after the simulator target is built? program works ok however.... Images For Q1 and Q2: For Q4: Settings used in Unity: Errors I see in XCode:

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