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  • How to structure class to support imported 3d model ?

    - by brainydexter
    Hello, I've written a C++ library that reads in this 3d model file (collada DAE). uptil now, I would output a list of triangles and handle each at rendering stage. But now, I need to attach some Bounding sphere information with the imported model. I need some advice on how should I organize this in code. Here are some specs of the 3D file format: - 3D model is represented as a Tree consisting of nodes - each node can contain other nodes, geometry information, transformation etc My requirements: - a bounding sphere associated with each node, thereby yielding a tree of bounding sphere hierarchy for the model itself. - actual vertex information What would be the recommended way to deal with this situation? Thanks

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  • Finding backedges in a graph, with special conditions.

    - by Morteza M.
    There is a vertex v, such that from the subtree rooted at v, there are at least two backedges to proper ancestors of v. The problem is finding whether such backedges exist or not ( finding v is not important at all). I run DFS algorithm, I can find backedges and save them in an array. I know which backedges in this array belong to a common tree. but I have problem on matching this condition in O(E) time. can anyone help me with that?

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  • Why does gcc think that I am trying to make a function call in my template function signature?

    - by nieldw
    GCC seem to think that I am trying to make a function call in my template function signature. Can anyone please tell me what is wrong with the following? 227 template<class edgeDecor, class vertexDecor, bool dir> 228 vector<Vertex<edgeDecor,vertexDecor,dir>> Graph<edgeDecor,vertexDecor,dir>::vertices() 229 { 230 return V; 231 }; GCC is giving the following: graph.h:228: error: a function call cannot appear in a constant-expression graph.h:228: error: template argument 3 is invalid graph.h:228: error: template argument 1 is invalid graph.h:228: error: template argument 2 is invalid graph.h:229: error: expected unqualified-id before ‘{’ token Thanks a lot.

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  • HLSL How can one pass data between shaders / read existing colour value?

    - by RJFalconer
    Hello all, I have 2 HLSL ps2.0 shaders. Simplified, they are: Shader 1 Reads texture Outputs colour value based on this texture Shader 2 Needs to read in existing colour (or have it passed in/read from a register) Outputs the final colour which is a function of the previous colour (They need to be different shaders as I've reached the maximum vertex-shader outputs for 1 shader) My problem is I cannot work out how Shader 2 can access the existing fragment/pixel colour. Is the only way for shaders to interact really just the alpha blending options? These aren't sufficient if I want to use the colour as input to my function.

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  • Is java.util.Scanner that slow?

    - by Cristian Vrabie
    Hi guys, In a Android application I want to use Scanner class to read a list of floats from a text file (it's a list of vertex coordinates for OpenGL). Exact code is: Scanner in = new Scanner(new BufferedInputStream(getAssets().open("vertexes.off"))); final float[] vertexes = new float[nrVertexes]; for(int i=0;i<nrVertexFloats;i++){ vertexes[i] = in.nextFloat(); } It seems however that this is incredibly slow (it took 30 minutes to read 10,000 floats!) - as tested on the 2.1 emulator. What's going on? I don't remember Scanner to be that slow when I used it on the PC (truth be told I never read more than 100 values before). Or is it something else, like reading from an asset input stream? Thanks for the help!

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  • Triangular bounding volumes

    - by Cheery
    I've come up with an alternative for beziers that might be easier to ray-trace, perhaps even though a plain vertex shader. Though there's missing a piece. I need to find the parametric surface equation from the surface normals I have for edge vertices. I also have to know it's peak and valley so I can constraint the depth of my bounding triangle. Image explains the overall idea: I build a bounding-volume from a control triangle. Then apply a function to each parametric coordinate of the triangle (s+t+u=1 where s,t,u = 0) to get the height coordinate for that certain point. Simply put, it produces a procedurally generated height-map for the triangle's surface. I just need to find a function that generates the height-map so I can make it work.

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  • Assigning a material in Blender with a script

    - by Narcolapser
    Question: How do you assign a material with a script to an object in blender? Info: I have this script to import a proprietary model type of mine that is basically a star map with object consisting of a single vertex. in order to make them look like stars and be visible they are all going to have a halo material assigned to them. I'm figuring out how to make this material and give it the values just fine, but I can't seem to get it to assign. I tried the most obvious thing which was: objectName.setMaterial(materialName) but that did nothing. and when i would take an object that had a material and call the getMaterial function on it, it would return nothing. there is something I'm missing here, can some one shed some light on it? Thanks. ~TA

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  • Wavefront obj loader iphone materials problem

    - by Magda
    Hi! I use Bill Duney wavefront obj loader. I'm new in opengles and it was really helpful. unfortunately... I exported a revit file to dwg and then open it with blender/google sketchUp and then to wavefront obj. Next, add my files to your loader and got strange results. The project load correctly vertex and normals but does a strange results with materials (I use only material, without textures). The one file is loaded with some materials on different faces the other, doesn't load materials but after a click makes the model green. If you have a minute and could help me out, please. I uploaded the project here. http://www.sendspace.pl/file/ecd348a3674ed1fe6eb10e5 Thanks for answering, Magda

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  • Optimally reducing maximum flow

    - by ArIck
    Given a parameter k, I'm trying to delete k edges from a directed graph such that the maximum flow is reduced by as much as possible. The graph has a source s and a sink t, and the capacity of each edge is one. The graph may or may not contain cycles. My proposed solution would be to first perform a topological sorting on the graph, using an algorithm that "forgives" cycles -- perhaps by ignoring edges that lead us back to the source. Then (assuming k = 1): i = 0 for each vertex u order by topological(u) for each edge (u, v) order by topological(v) descending if topological(v) > topological(u) then delete (u, v) if ++i = k then return else // edge doesn't contribute to max flow, ignore Would this work, or am I totally off-track here?

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  • Finding the centroid of a polygon?

    - by user146780
    I have tried: for each vertex, add to total, divide by number of verities to get center. I'v also tried: Find the topmost, bottommost - get midpoint... find leftmost, rightmost, find midpoint. Both of these did not return the perfect center because I'm relying on the center to scale a polygon. I want to scale my polygons so I may put a border around them. What is the best way to find the centroid of a polygon given that the polygon may be concave, convex and have many many sides of various lengths. Thanks

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  • OpenGL ES 2.0 Rendering with a Texture

    - by Kyle
    The iPhone SDK has an example of using ES 2.0 with a set of (Vertex & Fragment) GLSL shaders to render a varying colored box. Is there an example out there on how to render a simple texture using this API? I basically want to take a quad, and draw a texture onto it. The old ES 1.1 API's don't work at all anymore, so I'm needing a bit of help getting started. Most shader references talk mainly about advanced shading topics, but I'm really unsure about how to tell the shader to use the bound texture, and how to reference the UV's. Thanks!

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  • How can I use STL sort in c++ to sort some values in the class?

    - by Morteza M.
    I have a class named Graph, in this class I have a member named V, it is a vector. I have a struct named Edge, and a list of Edges. like below: struct Edge{ int u; int v; Edge(int u,int v){ this-u=u; this-v=v; } }; class Graph{ vector < Vertex > V; . . . int edgeCmp(Edge* x,Edge* y){ return (V[x-v].dv].d)?1:0; } void someFunction(){ list backEdges; backEdges.sort(&Graph::edgeCmp); } } But it doesn't work!! may someone help me to do such a thing?

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  • Find the centroid of a polygon with weighted vertices

    - by Calle Kabo
    Hi, I know how to find the centroid (center of mass) of a regular polygon. This assumes that every part of the polygon weighs the same. But how do I calculate the centroid of a weightless polygon (made from aerogel perhaps :), where each vertex has a weight? Simplified illustration of what I mean using straight line: 5kg-----------------5kg ^center of gravity 10kg---------------5kg ^center of gravity offset du to weight of vertices Of course, I know how to calculate the center of gravity on a straight line with weighted vertices, but how do I do it on a polygon with weighted vertices? Thanks for your time!

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  • How do I get an Iterator over a vector of objects from a Template?

    - by nieldw
    I'm busy implementing a Graph ADT in C++. I have templates for the Edges and the Vertices. At each Vertex I have a vector containing pointers to the Edges that are incident to it. Now I'm trying to get an iterator over those edges. These are the lines of code: vector<Edge<edgeDecor, vertexDecor, dir>*> edges = this->incidentEdges(); vector<Edge<edgeDecor, vertexDecor, dir>*>::const_iterator i; for (i = edges.begin(); i != edges.end(); ++i) { However, the compiler won't accept the middle line. I'm pretty new to C++. Am I missing something? Why can't I declare an iterator over objects from the Edge template? The compiler isn't giving any useful feedback. Much thanks niel

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  • WebGL transparent black.

    - by Catalin Dumitru
    I have a strange problem that I can't figure out when trying to do blending in WebGL. Black is rendered fully transparent , and everything with shades of grey in it is rendered also semi transparent. I have set it to use the alpha channel as the source for transparency, and in some respect it works, every thing that isn't black/grey is rendered differently when changing the alpha value. but even when I set the alpha to 1, black is still displayed transparent. This is how I enable transparency: this.gl.blendFunc(this.gl.SRC_ALPHA, this.gl.ONE); this.gl.enable(this.gl.BLEND); this.gl.disable(this.gl.DEPTH_TEST); And the part of the shader that does transparency: gl_FragColor = vec4(texColor.rgb * vLightWeight, texColor.a * uAlpha); where texColor is the texture color that is being sampled, vLightWeight is the shadowing that is being calculated in the vertex shader, and uAlpha the uniform which I use for transparency.

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  • Generating a beveled edge for a 2D polygon

    - by Metaphile
    I'm trying to programmatically generate beveled edges for geometric polygons. For example, given an array of 4 vertices defining a square, I want to generate something like this. But computing the vertices of the inner shape is baffling me. Simply creating a copy of the original shape and then scaling it down will not produce the desired result most of the time. My algorithm so far involves analyzing adjacent edges (triples of vertices; e.g., the bottom-left, top-left, and top-right vertices of a square). From there, I need to find the angle between them, and then create a vertex somewhere along that angle, depending on how deep I want the bevel to be. And because I don't have much of a math background, that's where I'm stuck. How do I find that center angle? Or is there a much simpler way of attacking this problem?

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  • Trying to draw textured triangles on device fails, but the emulator works. Why?

    - by Dinedal
    I have a series of OpenGL-ES calls that properly render a triangle and texture it with alpha blending on the emulator (2.0.1). When I fire up the same code on an actual device (Droid 2.0.1), all I get are white squares. This suggests to me that the textures aren't loading, but I can't figure out why they aren't loading. All of my textures are 32-bit PNGs with alpha channels, under res/raw so they aren't optimized per the sdk docs. Here's how I am loading my textures: private void loadGLTexture(GL10 gl, Context context, int reasource_id, int texture_id) { //Get the texture from the Android resource directory Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), reasource_id, sBitmapOptions); //Generate one texture pointer... gl.glGenTextures(1, textures, texture_id); //...and bind it to our array gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[texture_id]); //Create Nearest Filtered Texture gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); //Different possible texture parameters, e.g. GL10.GL_CLAMP_TO_EDGE gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT); //Use the Android GLUtils to specify a two-dimensional texture image from our bitmap GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0); //Clean up bitmap.recycle(); } Here's how I am rendering the texture: //Clear gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); //Enable vertex buffer gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer); //Push transformation matrix gl.glPushMatrix(); //Transformation matrices gl.glTranslatef(x, y, 0.0f); gl.glScalef(scalefactor, scalefactor, 0.0f); gl.glColor4f(1.0f,1.0f,1.0f,1.0f); //Bind the texture gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[textureid]); //Draw the vertices as triangles gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer); //Pop the matrix back to where we left it gl.glPopMatrix(); //Disable the client state before leaving gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); And here are the options I have enabled: gl.glShadeModel(GL10.GL_SMOOTH); //Enable Smooth Shading gl.glEnable(GL10.GL_DEPTH_TEST); //Enables Depth Testing gl.glDepthFunc(GL10.GL_LEQUAL); //The Type Of Depth Testing To Do gl.glEnable(GL10.GL_TEXTURE_2D); gl.glEnable(GL10.GL_BLEND); gl.glBlendFunc(GL10.GL_SRC_ALPHA,GL10.GL_ONE_MINUS_SRC_ALPHA); Edit: I just tried supplying a BitmapOptions to the BitmapFactory.decodeResource() call, but this doesn't seem to fix the issue, despite manually setting the same preferredconfig, density, and targetdensity. Edit2: As requested, here is a screenshot of the emulator working. The underlaying triangles are shown with a circle texture rendered onto it, the transparency is working because you can see the black background. Here is a shot of what the droid does with the exact same code on it: Edit3: Here are my BitmapOptions, updated the call above with how I am now calling the BitmapFactory, still the same results as below: sBitmapOptions.inPreferredConfig = Bitmap.Config.RGB_565; sBitmapOptions.inDensity = 160; sBitmapOptions.inTargetDensity = 160; sBitmapOptions.inScreenDensity = 160; sBitmapOptions.inDither = false; sBitmapOptions.inSampleSize = 1; sBitmapOptions.inScaled = false; Here are my vertices, texture coords, and indices: /** The initial vertex definition */ private static final float vertices[] = { -1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f, -1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f }; /** The initial texture coordinates (u, v) */ private static final float texture[] = { //Mapping coordinates for the vertices 0.0f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f }; /** The initial indices definition */ private static final byte indices[] = { //Faces definition 0,1,3, 0,3,2 }; Is there anyway to dump the contents of the texture once it's been loaded into OpenGL ES? Maybe I can compare the emulator's loaded texture with the actual device's loaded texture? I did try with a different texture (the default android icon) and again, it works fine for the emulator but fails to render on the actual phone. Edit4: Tried switching around when I do texture loading. No luck. Tried using a constant offset of 0 to glGenTextures, no change. Is there something that I'm using that the emulator supports that the actual phone does not? Edit5: Per Ryan below, I resized my texture from 200x200 to 256x256, and the issue was NOT resolved. Edit: As requested, added the calls to glVertexPointer and glTexCoordPointer above. Also, here is the initialization of vertexBuffer, textureBuffer, and indexBuffer: ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); vertexBuffer = byteBuf.asFloatBuffer(); vertexBuffer.put(vertices); vertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(texture.length * 4); byteBuf.order(ByteOrder.nativeOrder()); textureBuffer = byteBuf.asFloatBuffer(); textureBuffer.put(texture); textureBuffer.position(0); indexBuffer = ByteBuffer.allocateDirect(indices.length); indexBuffer.put(indices); indexBuffer.position(0); loadGLTextures(gl, this.context);

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  • Is this possible with OpenGL?

    - by user146780
    Basically what I'd like to do is make textured NGONS. I also want to use a tesselator (GLU) to make concave and multicontour objects. I was wondering how the texture comes into play though. I think that the tesselator will return verticies so I will add these to my array, that's fine. But my vertex array will contain more than one polygon object so then how can I tell it when to bind the texture like in immediate mode? Right now I feel stuck with one call to bind. How can this be done? Thanks

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  • In a C++ template, is it allowed to return an object with spesific type parameters?

    - by nieldw
    When I've got a template with certain type parameters, is it allowed for a function to return an object of this same template, but with different types? In other words, is the following allowed? template<class edgeDecor, class vertexDecor, bool dir> Graph<edgeDecor,int,dir> Graph<edgeDecor,vertexDecor,dir>::Dijkstra(vertex s, bool print = false) const { /* Construct new Graph with apropriate decorators */ Graph<edgeDecor,int,dir> span = new Graph<edgeDecor,int,dir>(); /* ... */ return span; }; If this is not allowed, how can I accomplish the same kind of thing?

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  • 3D Mesh Joining

    - by morlst
    I have 2 (or more) intersecting meshes, which require joining into 1 mesh object. I want to have some control over the resulting seam vertex insertion, so looking to write myself rather than use a library. Has anyone come across some open source code to base the algorithm on / ideas on the process? Initial impressions are: 1. Present in every 3D modelling program - mostly reinventing existing process (hence search for examples) 2. Potential for fiddly-ness around the polygon face direction and just touching conditions. (see above point)

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  • Dynamically generate Triangle Lists for a Complex 3D Mesh

    - by Vulcan Eager
    In my application, I have the shape and dimensions of a complex 3D solid (say a Cylinder Block) taken from user input. I need to construct vertex and index buffers for it. Since the dimensions are taken from user input, I cannot user Blender or 3D Max to manually create my model. What is the textbook method to dynamically generate such a mesh? Edit: I am looking for something that will generate the triangles given the vertices, edges and holes. Something like TetGen. As for TetGen itself, I have no way of excluding the triangles which fall on the interior of the solid/mesh.

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  • Purely functional equivalent of weakhashmap?

    - by Jon Harrop
    Weak hash tables like Java's weak hash map use weak references to track the collection of unreachable keys by the garbage collector and remove bindings with that key from the collection. Weak hash tables are typically used to implement indirections from one vertex or edge in a graph to another because they allow the garbage collector to collect unreachable portions of the graph. Is there a purely functional equivalent of this data structure? If not, how might one be created? This seems like an interesting challenge. The internal implementation cannot be pure because it must collect (i.e. mutate) the data structure in order to remove unreachable parts but I believe it could present a pure interface to the user, who could never observe the impurities because they only affect portions of the data structure that the user can, by definition, no longer reach.

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  • Opengl ES and texcoord

    - by viraptor
    Hi, I've got some code which I would like to translate into Opengl ES. I'm not experienced with it however, so here it goes. The original code does a loop like this: glBegin(GL_TRIANGLES); for(i=0; i<num_triangles; i++) { glNormal(...); glTexCoord2f(...); glVerted3fv(...); glTexCoord2f(...); glVerted3fv(...); glTexCoord2f(...); glVerted3fv(...); } glEnd(); So that's ok - I can change the vertex handling for each triangle in the loop, into the standard: glEnableClientState (GL_VERTEX_ARRAY); glVertexPointer (3, GL_SOMETHING, 0, verts); glDrawArrays (GL_TRIANGLES, 0, 3); But how do I add the texcoord setting into this example?

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  • Weakly connected balanced digraph

    - by user1074557
    How can I prove that if a balanced digraph is weakly connected, then it is also strongly connected? (balanced digraph means that for every node, it's indegree and outdegree is the same and weakly connected means the non-directed version of this graph is connected). What I can think of so far is: if the graph is balanced, it means it is a union of directed cycles. So if I remove any cycle, it will stay balanced. Also each vertex in the cycle has one edge coming into it and one edge leading out of it.. Then I guess I need to use some contradiction or induction to prove that the graph is strongly connected.. That's where I confused.

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  • In a C++ template, is it allowed to return an object with specific type parameters?

    - by nieldw
    When I've got a template with certain type parameters, is it allowed for a function to return an object of this same template, but with different types? In other words, is the following allowed? template<class edgeDecor, class vertexDecor, bool dir> Graph<edgeDecor,int,dir> Graph<edgeDecor,vertexDecor,dir>::Dijkstra(vertex s, bool print = false) const { /* Construct new Graph with apropriate decorators */ Graph<edgeDecor,int,dir> span = new Graph<edgeDecor,int,dir>(); /* ... */ return span; }; If this is not allowed, how can I accomplish the same kind of thing?

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