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  • How do I convert a partially transparent image into polygons?

    - by user82779
    I'm using GLEE2D, a level editor allowing me to import images, scale them, rotate them, and position them onto layers and export the data into XML format. However, it does not tell me objects' boundaries. I can calculate them, but only given the original image's polygons. How do I get polygons of objects in a transparent image? An example object (I outlined it): How would I turn the object, knowing the scaled size of the image, into polygons? Is there an algorithm for this? I'll use OpenGL to draw them.

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  • Openlayers and Bing Maps (POLYGONS)

    - by Jordan
    When trying to draw polygons onto a bing map, the initial marker is set differently on the map. How can I fix this? OpenLayers Bing Example <script src="OpenLayers.js"></script> <script> var map; function init(){ map = new OpenLayers.Map("map"); map.addControl(new OpenLayers.Control.LayerSwitcher()); var shaded = new OpenLayers.Layer.VirtualEarth("Shaded", { type: VEMapStyle.Shaded }); var hybrid = new OpenLayers.Layer.VirtualEarth("Hybrid", { type: VEMapStyle.Hybrid }); var aerial = new OpenLayers.Layer.VirtualEarth("Aerial", { type: VEMapStyle.Aerial }); var POLY_LAYER = new OpenLayers.Layer.Vector(); map.addLayers([shaded, hybrid, aerial, POLY_LAYER]); map.setCenter(new OpenLayers.LonLat(-110, 45), 3); var polygon = new OpenLayers.Control.DrawFeature(POLY_LAYER, OpenLayers.Handler.Polygon); map.addControl(polygon); polygon.activate(); } </script> Bing Example <div id="tags"> Bing, Microsoft, Virtual Earth </div> <p id="shortdesc"> Demonstrates the use of Bing layers. </p> <div id="map" class="smallmap"></div> <div id="docs">This example demonstrates the ability to create layers using tiles from Bing maps.</div> Of course the above is being initialized and page works. You can draw the polygon shapes. Notice if you zoom in or out one time, the markers are set at the correct coordinates. My app I was testing this on is really using the bing maps API keys and not VirtualEarth. But it's doing a similar thing. Is this an Openlayers bug? The below source came directly from the open layers example site, I just added and activated polygons to the map. Please let me know how I can fix this for using the Bing Map API.. I've been stuck on this for HOURS! :(

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  • Intersections of 3D polygons in python

    - by Andrew Walker
    Are there any open source tools or libraries (ideally in python) that are available for performing lots of intersections with 3D geometry read from an ESRI shapefile? Most of the tests will be simple line segments vs polygons. I've looked into OGR 1.7.1 / GEOS 3.2.0, and whilst it loads the data correctly, the resulting intersections aren't correct, and most of the other tools available seem to build on this work. Whilst CGAL would have been an alternative, it's license isn't suitable. The Boost generic geometry library looks fantastic, but the api is huge, and doesn't seem to support wkt or wkb readers out of the box.

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  • Union of complex polygons

    - by grenade
    Given two polygons: POLYGON((1 0, 1 8, 6 4, 1 0)) POLYGON((4 1, 3 5, 4 9, 9 5, 4 1),(4 5, 5 7, 6 7, 4 4, 4 5)) How can I calculate the union (combined polygon)? Dave's example uses SQL server to produce the union, but I need to accomplish the same in code. I'm looking for a mathematical formula or code example in any language that exposes the actual math. I am attempting to produce maps that combine countries dynamically into regions. I asked a related question here: http://stackoverflow.com/questions/2653812/grouping-geographical-shapes

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  • GIS: Converting multi polygons to multiple features

    - by Kangkan
    Hi, I am involved in a GIS project. I have a base map file (shape file) that contains the road layer for a large portion of a town. The problem is that the shape file contains only two features each containing around 500000 points each. The features are multipolygons containing a large no of polygons inside. I wish to convert it to numerous features each containing not more than one polygon. Is it possible? If yes, how?

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  • Best way to search a point across several polygons

    - by user1474341
    I have a requirement whereby I need to match a given point (lat,lon) against several polygons to decide if there is a match. The easiest way would be to iterative over each polygon and apply the point-in-polygon check algorithm, but that is prohibitively expensive. The next optimization that I did was to define a bounding rectangle for each polygon (upper bound, lower bound) and iteratively check the point against the bounding box (fewer comparisons as against checking all the points in the polygon). Is there any other optimization possible? Would a spatial index on the bound rectangle points or a geohash help ? Any guidance would be greatly appreciated. Thanks!

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  • Reformat SQLGeography polygons to JSON

    - by James
    I am building a web service that serves geographic boundary data in JSON format. The geographic data is stored in an SQL Server 2008 R2 database using the geography type in a table. I use [ColumnName].ToString() method to return the polygon data as text. Example output: POLYGON ((-6.1646509904325884 56.435153006374627, ... -6.1606079906751 56.4338050060666)) MULTIPOLYGON (((-6.1646509904325884 56.435153006374627 0 0, ... -6.1606079906751 56.4338050060666 0 0))) Geographic definitions can take the form of either an array of lat/long pairs defining a polygon or in the case of multiple definitions, an array or polygons (multipolygon). I have the following regex that converts the output to JSON objects contained in multi-dimensional arrays depending on the output. Regex latlngMatch = new Regex(@"(-?[0-9]{1}\.\d*)\s(\d{2}.\d*)(?:\s0\s0,?)?", RegexOptions.Compiled); private string ConvertPolysToJson(string polysIn) { return this.latlngMatch.Replace(polysIn.Remove(0, polysIn.IndexOf("(")) // remove POLYGON or MULTIPOLYGON .Replace("(", "[") // convert to JSON array syntax .Replace(")", "]"), // same as above "{lng:$1,lat:$2},"); // reformat lat/lng pairs to JSON objects } This is actually working pretty well and converts the DB output to JSON on the fly in response to an operation call. However I am no regex master and the calls to String.Replace() also seem inefficient to me. Does anyone have any suggestions/comments about performance of this?

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  • OpenGL, draw two polygons in the same time (by mouse clicks)

    - by YoungSalafi
    im trying to draw 2 polygons at the same time depending on user input from the opengl screen... so i made 2 arrays which each one of them will carry the vertices of each polygon ... i think my logic is right but the program still prints only polygon and delete the old polygon if you draw a polygon again . and its acting weird too please check the code yourself here it is : P.S dont mind the delete function right now.. i know it missing something. #include <windows.h> #include <gl/gl.h> #include <gl/glut.h> void Draw(); void Set_Transformations(); void Initialize(int argc, char *argv[]); void OnKeyPress(unsigned char key, int x, int y); void DeleteVer(); void MouseClick(int bin, int state , int x , int y); void GetOGLPos(int x, int y,float* arrY,float* arrX); void DrawPolygon(float* arrX,float* arrY); float xPos[20]; float yPos[20]; float xPos2[20]; float yPos2[20]; float fx = 0,fy = 0; float size = 10; int count = 0; bool done = false; bool flag = true; void Initialize(int argc, char *argv[]) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGBA); glutInitWindowPosition(100, 100); glutInitWindowSize(600, 600); glutCreateWindow("OpenGL Lab1"); Set_Transformations(); glutDisplayFunc(Draw); glutMouseFunc(MouseClick); glutKeyboardFunc(OnKeyPress); glutMainLoop(); } void Set_Transformations() { glClearColor(1, 1, 1, 1); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluOrtho2D(-200, 200, -200, 200); } void OnKeyPress(unsigned char key, int x, int y) { if (key == 27) exit(0); switch(key) { case 13: //enter key it will draw done = true; glutPostRedisplay(); flag=!flag; // this flag to switch to the other array that the vertices will be stored in, in order to draw the second polygon break; } } void MouseClick(int button, int state , int x , int y) { switch (button) { case GLUT_RIGHT_BUTTON: if (state == GLUT_DOWN) { if (count>0) { DeleteVer(); //dont mind this right now } } break; case GLUT_LEFT_BUTTON: if (state == GLUT_DOWN) { if(count<20) { if(flag =true){ // drawing first polygon GetOGLPos(x, y,xPos,yPos);} if (flag=false) //drawing second polygon after Enter is pressed GetOGLPos(x, y,xPos2,yPos2); } } break; } } void GetOGLPos(int x, int y,float* arrY,float* arrX) //getting the vertices from the user { GLint viewport[4]; GLdouble modelview[16]; GLdouble projection[16]; GLfloat winX, winY, winZ; GLdouble posX, posY, posZ; glGetDoublev( GL_MODELVIEW_MATRIX, modelview ); glGetDoublev( GL_PROJECTION_MATRIX, projection ); glGetIntegerv( GL_VIEWPORT, viewport ); winX = (float)x; winY = (float)viewport[3] - (float)y; glReadPixels( x, int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ ); gluUnProject( winX, winY, winZ, modelview, projection, viewport, &posX, &posY, &posZ); arrX[count] = posX; arrY[count] = posY; count++; glPointSize( 6.0 ); glBegin(GL_POINTS); glVertex2f(posX,posY); glEnd(); glFlush(); } void DeleteVer(){ //dont mind this glColor3f ( 1, 1, 1); glBegin(GL_POINTS); glVertex2f(xPos[count-1],yPos[count-1]); glEnd(); glFlush(); xPos[count] = NULL; yPos[count] = NULL; count--; glColor3f ( 0, 0, 0); } void DrawPolygon(float* arrX,float* arrY) { int n=0; glColor3f ( 0, 0, 0); glBegin(GL_POLYGON); while(n<count) { glVertex2f(arrX[n],arrY[n]); n++; } count=0; glEnd(); glFlush(); } void Draw() //main drawing func { glClear(GL_COLOR_BUFFER_BIT); glColor3f(0, 0, 0); if(done) { DrawPolygon(xPos,yPos); DrawPolygon(xPos2,yPos2); } glFlush(); } int main(int argc, char *argv[]) { Initialize(argc, argv); return 0; }

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  • good methods for boolean operations on overlapping polygons

    - by BenjaminGolder
    What is the best open source library for performing boolean operations (union, intersect, subtract) on shapefiles? What do you like to use? OGR looks like it probably has this capability, though I'm having trouble finding the particular commands in their documentation. Shapely definitely does this, and is easy to understand. PostGIS appears to also have some commands for this. But there must be more, and I'm having trouble finding them. I don't have much experience with any of the, and would appreciate any opinions on these or other libraries. Thanks!

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  • OpenGL - Frustum not culling polygons beyond far plane

    - by Pladnius Brooks
    I have implemented frustum culling and am checking the bounding box for its intersection with the frustum planes. I added the ability to pause frustum updates which lets me see if the frustum culling has been working correctly. When I turn around after I have paused it, nothing renders behind me and to the left and right side, they taper off as well just as you would expect. Beyond the clip distance (far plane), they still render and I am not sure whether it is a problem with my frustum updating or bounding box checking code or I am using the wrong matrix or what. As I put the distance in the projection matrix at 3000.0f, it still says that bounding boxes well past that are still in the frustum, which isn't the case. Here is where I create my modelview matrix: projectionMatrix = glm::perspective(newFOV, 4.0f / 3.0f, 0.1f, 3000.0f); viewMatrix = glm::mat4(1.0); viewMatrix = glm::scale(viewMatrix, glm::vec3(1.0, 1.0, -1.0)); viewMatrix = glm::rotate(viewMatrix, anglePitch, glm::vec3(1.0, 0.0, 0.0)); viewMatrix = glm::rotate(viewMatrix, angleYaw, glm::vec3(0.0, 1.0, 0.0)); viewMatrix = glm::translate(viewMatrix, glm::vec3(-x, -y, -z)); modelViewProjectiomMatrix = projectionMatrix * viewMatrix; The reason I scale it by -1 in the Z direction is because the levels were designed to be rendered with DirectX so I reverse the Z direction. Here is where I update my frustum: void CFrustum::calculateFrustum() { glm::mat4 mat = camera.getModelViewProjectionMatrix(); // Calculate the LEFT side m_Frustum[LEFT][A] = (mat[0][3]) + (mat[0][0]); m_Frustum[LEFT][B] = (mat[1][3]) + (mat[1][0]); m_Frustum[LEFT][C] = (mat[2][3]) + (mat[2][0]); m_Frustum[LEFT][D] = (mat[3][3]) + (mat[3][0]); // Calculate the RIGHT side m_Frustum[RIGHT][A] = (mat[0][3]) - (mat[0][0]); m_Frustum[RIGHT][B] = (mat[1][3]) - (mat[1][0]); m_Frustum[RIGHT][C] = (mat[2][3]) - (mat[2][0]); m_Frustum[RIGHT][D] = (mat[3][3]) - (mat[3][0]); // Calculate the TOP side m_Frustum[TOP][A] = (mat[0][3]) - (mat[0][1]); m_Frustum[TOP][B] = (mat[1][3]) - (mat[1][1]); m_Frustum[TOP][C] = (mat[2][3]) - (mat[2][1]); m_Frustum[TOP][D] = (mat[3][3]) - (mat[3][1]); // Calculate the BOTTOM side m_Frustum[BOTTOM][A] = (mat[0][3]) + (mat[0][1]); m_Frustum[BOTTOM][B] = (mat[1][3]) + (mat[1][1]); m_Frustum[BOTTOM][C] = (mat[2][3]) + (mat[2][1]); m_Frustum[BOTTOM][D] = (mat[3][3]) + (mat[3][1]); // Calculate the FRONT side m_Frustum[FRONT][A] = (mat[0][3]) + (mat[0][2]); m_Frustum[FRONT][B] = (mat[1][3]) + (mat[1][2]); m_Frustum[FRONT][C] = (mat[2][3]) + (mat[2][2]); m_Frustum[FRONT][D] = (mat[3][3]) + (mat[3][2]); // Calculate the BACK side m_Frustum[BACK][A] = (mat[0][3]) - (mat[0][2]); m_Frustum[BACK][B] = (mat[1][3]) - (mat[1][2]); m_Frustum[BACK][C] = (mat[2][3]) - (mat[2][2]); m_Frustum[BACK][D] = (mat[3][3]) - (mat[3][2]); // Normalize all the sides NormalizePlane(m_Frustum, LEFT); NormalizePlane(m_Frustum, RIGHT); NormalizePlane(m_Frustum, TOP); NormalizePlane(m_Frustum, BOTTOM); NormalizePlane(m_Frustum, FRONT); NormalizePlane(m_Frustum, BACK); } And finally, where I check the bounding box: bool CFrustum::BoxInFrustum( float x, float y, float z, float x2, float y2, float z2) { // Go through all of the corners of the box and check then again each plane // in the frustum. If all of them are behind one of the planes, then it most // like is not in the frustum. for(int i = 0; i < 6; i++ ) { if(m_Frustum[i][A] * x + m_Frustum[i][B] * y + m_Frustum[i][C] * z + m_Frustum[i][D] > 0) continue; if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y + m_Frustum[i][C] * z + m_Frustum[i][D] > 0) continue; if(m_Frustum[i][A] * x + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z + m_Frustum[i][D] > 0) continue; if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z + m_Frustum[i][D] > 0) continue; if(m_Frustum[i][A] * x + m_Frustum[i][B] * y + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0) continue; if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0) continue; if(m_Frustum[i][A] * x + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0) continue; if(m_Frustum[i][A] * x2 + m_Frustum[i][B] * y2 + m_Frustum[i][C] * z2 + m_Frustum[i][D] > 0) continue; // If we get here, it isn't in the frustum return false; } // Return a true for the box being inside of the frustum return true; }

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  • OpenGL - drawing 2D polygons shapes with texture

    - by plonkplonk
    I am trying to make a few effects in a C+GL game. So far I draw all my sprites as a quad, and it works. However, I am trying to make a large ring appear at times, with a texture following that ring, as it takes less memory than a quad with the ring texture inside. The type of ring I want to make is not a round-shaped GL mesh ring (the "tube" type) but a "paper" 2D ring. That way I can modify the "width" of the ring, getting more of the effect than a simple quad+ring texture. So far all my attempts have been...kind of ridiculous, as I don't understand GL's coordinates too well (and I can't really understand the available documentation...I am just a designer with no coder help or background. A n00b, basically). glBegin(GL_POLYGON); for(i = 0;i < 360; i += 10){ glTexCoord2f(0, 0); glVertex2f(Cos(i)*(H-10),Sin(i)H); glTexCoord2f(0, HP); glVertex2f(Sin(i)(H-10),Cos(i)*(H-10)); glTexCoord2f(WP, HP); glVertex2f(Cos(i)H,Sin(i)(H-10)); glTexCoord2f(WP, 0); glVertex2f(Sin(i)*H,Cos(i)*H); } glEnd(); This is my last attempt, and it seems to generate a "sunburst" from the right edge of the circle instead of a ring. It's an amusing effect but definitely not what I want. Other results included the circle looking exactly the same as the quad textured (aka drawing a sprite literally) or something that looked like a pop-art filter, by working on this train of thought. Seems like my logic here is entirely flawed, so, what would be the easiest way to obtain such a ring? No need to reply in code, just some guidance for a non-math-skilled user...

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  • OpenGL polygons stuck at top left?

    - by user146780
    I'm using theallegro library and through it OpenGL. I enable depth testing, then upon resize I do: glEnable(GL_CULL_FACE); glCullFace(GL_BACK); glEnable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glFrustum(0,event.display.width,event.display.height,0,1,300); Then my drawing looks like: float BOX_SIZE = 200.0f; glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glRotatef(0.5, 0, 0.0f, 1.0f); glBegin(GL_QUADS); //Top face glColor3f(1.0f, 1.0f, 0.0f); glNormal3f(0.0, 1.0f, 0.0f); glVertex3f(500 + -BOX_SIZE / 2, BOX_SIZE / 2, -BOX_SIZE / 2); glVertex3f(500 + -BOX_SIZE / 2, BOX_SIZE / 2, BOX_SIZE / 2); glVertex3f(500 + BOX_SIZE / 2, BOX_SIZE / 2, BOX_SIZE / 2); glVertex3f(500 + BOX_SIZE / 2, BOX_SIZE / 2, -BOX_SIZE / 2); //Bottom face glColor3f(1.0f, 0.0f, 1.0f); glNormal3f(0.0, -1.0f, 0.0f); glVertex3f(-BOX_SIZE / 2, -BOX_SIZE / 2, -BOX_SIZE / 2); glVertex3f(BOX_SIZE / 2, -BOX_SIZE / 2, -BOX_SIZE / 2); glVertex3f(BOX_SIZE / 2, -BOX_SIZE / 2, BOX_SIZE / 2); glVertex3f(-BOX_SIZE / 2, -BOX_SIZE / 2, BOX_SIZE / 2); //Left face glNormal3f(-1.0, 0.0f, 0.0f); glColor3f(0.0f, 1.0f, 1.0f); glVertex3f(-BOX_SIZE / 2, -BOX_SIZE / 2, -BOX_SIZE / 2); glVertex3f(-BOX_SIZE / 2, -BOX_SIZE / 2, BOX_SIZE / 2); glColor3f(0.0f, 0.0f, 1.0f); glVertex3f(-BOX_SIZE / 2, BOX_SIZE / 2, BOX_SIZE / 2); glVertex3f(-BOX_SIZE / 2, BOX_SIZE / 2, -BOX_SIZE / 2); //Right face glNormal3f(1.0, 0.0f, 0.0f); glColor3f(1.0f, 0.0f, 0.0f); glVertex3f(BOX_SIZE / 2, -BOX_SIZE / 2, -BOX_SIZE / 2); glVertex3f(BOX_SIZE / 2, BOX_SIZE / 2, -BOX_SIZE / 2); glColor3f(0.0f, 1.0f, 0.0f); glVertex3f(BOX_SIZE / 2, BOX_SIZE / 2, BOX_SIZE / 2); glVertex3f(BOX_SIZE / 2, -BOX_SIZE / 2, BOX_SIZE / 2); glEnd(); glEnable(GL_TEXTURE_2D); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glColor3f(1.0f, 1.0f, 1.0f); glBegin(GL_QUADS); //Front face glNormal3f(0.0, 0.0f, 1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-BOX_SIZE / 2, -BOX_SIZE / 2, BOX_SIZE / 2); glTexCoord2f(1.0f, 0.0f); glVertex3f(BOX_SIZE / 2, -BOX_SIZE / 2, BOX_SIZE / 2); glTexCoord2f(1.0f, 1.0f); glVertex3f(BOX_SIZE / 2, BOX_SIZE / 2, BOX_SIZE / 2); glTexCoord2f(0.0f, 1.0f); glVertex3f(-BOX_SIZE / 2, BOX_SIZE / 2, BOX_SIZE / 2); //Back face glNormal3f(0.0, 0.0f, -1.0f); glTexCoord2f(0.0f, 0.0f); glVertex3f(-BOX_SIZE / 2, -BOX_SIZE / 2, -BOX_SIZE / 2); glTexCoord2f(1.0f, 0.0f); glVertex3f(-BOX_SIZE / 2, BOX_SIZE / 2, -BOX_SIZE / 2); glTexCoord2f(1.0f, 1.0f); glVertex3f(BOX_SIZE / 2, BOX_SIZE / 2, -BOX_SIZE / 2); glTexCoord2f(0.0f, 1.0f); glVertex3f(BOX_SIZE / 2, -BOX_SIZE / 2, -BOX_SIZE / 2); glEnd(); glDisable(GL_TEXTURE_2D); //code goes here al_flip_display(); for some reason the cube no matter how I translate it seems to extend from 0,0 and theres always a vertex at 0,0. What have I done wrong? Thanks

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  • Representing geographical points/polygons in Python/Django

    - by Cornflake
    I'm building a website in Django, and I want one of my datatypes to be a geographical polygon. I want to mark points on a map (say, in Google Maps) and then store the resulting polygon in the database. Is there any way to do it that will save me the work of typing all the longitudes and latitudes manually? I guess I'm looking both for a geographical library for Python, and for a special website that will let me mark points on the map and save them in a standard format. Thanks!

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  • Black outline around map polygons (IE)

    - by user146780
    This only happens in some IE's. Here: http://animactions.ca/Animactions/volet_entreprise.php You may notice that when you click and drag on one of the circles, you will get something similar to this: http://img534.imageshack.us/img534/7578/errorra.png I cannot figure it out. Here is my image map: <p class="style2"> <map id="FPMap0" name="FPMap0"> <area coords="405, 8, 375, 10, 353, 13, 322, 30, 317, 48, 327, 69, 344, 75, 370, 84, 401, 86, 428, 81, 454, 69, 466, 56, 468, 37, 452, 19, 419, 9" href="le_developpement_des_equipes_de_travail.php" shape="poly" style="outline:0" target="_blank" /> <area coords="95, 164, 65, 166, 43, 174, 21, 186, 16, 206, 27, 225, 48, 237, 76, 241, 99, 241, 129, 236, 151, 228, 165, 214, 167, 194, 154, 177, 130, 168, 105, 165" href="le_developpement_operationnel.php" shape="poly" style="outline:0" target="_blank" /> <area coords="138, 17, 115, 7, 95, 8, 63, 8, 41, 20, 21, 35, 23, 60, 42, 74, 77, 83, 117, 86, 144, 76, 164, 62, 173, 40, 156, 21, 137, 12" href="coaching_strategique_de_cadre.php" shape="poly" style="border-width:0" target="_blank" /> </map> <img alt="services entreprise" height="258" src="Images/service_ent.PNG" width="490" usemap="#FPMap0" /></p> I really hope someone can figure this out because I'v tried everything... Thanks

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  • Plotting 3D Polygons in python-matplotlib

    - by Developer
    I was unsuccessful browsing web for a solution for the following simple question: How to draw 3D polygon (say a filled rectangle or triangle) using vertices values? I have tried many ideas but all failed, see: from mpl_toolkits.mplot3d import Axes3D from matplotlib.collections import PolyCollection import matplotlib.pyplot as plt fig = plt.figure() ax = Axes3D(fig) x = [0,1,1,0] y = [0,0,1,1] z = [0,1,0,1] verts = [zip(x, y,z)] ax.add_collection3d(PolyCollection(verts),zs=z) plt.show() I appreciate in advance any idea/comment. Updates based on the accepted answer: import mpl_toolkits.mplot3d as a3 import matplotlib.colors as colors import pylab as pl import scipy as sp ax = a3.Axes3D(pl.figure()) for i in range(10000): vtx = sp.rand(3,3) tri = a3.art3d.Poly3DCollection([vtx]) tri.set_color(colors.rgb2hex(sp.rand(3))) tri.set_edgecolor('k') ax.add_collection3d(tri) pl.show() Here is the result:

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  • n*n blocks and polygons

    - by OSaad
    Hi, this is actually meant to be for a function called roipoly in matlab but it can be considered a general case problem. Roipoly is a function which lets u select a polygon over an image, and returns a binary mask where u can use it to get indices of the desired polygon. (It is just a normal polygon after all). My application (K-Nearest Neighbor) requires that i make n*n blocks out of the data i have (the polygon), i.e. If i have a polygon (a road or a piece of land), i want a n*n square moving over it while avoiding intersection with edges and putting those n*n pixels into some variable. This problem would be a lot easier if i had all my shapes in the form of rectangles, but that unfortunately isn't the case. I might have something going diagonal, circular or just irregular.

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  • How to calculate the normal of points on a 3D cubic Bézier curve given normals for its start and end points?

    - by Robert
    I'm trying to render a "3D ribbon" using a single 3D cubic Bézier curve to describe it (the width of the ribbon is some constant). The first and last control points have a normal vector associated with them (which are always perpendicular to the tangents at those points, and describe the surface normal of the ribbon at those points), and I'm trying to smoothly interpolate the normal vector over the course of the curve. For example, given a curve which forms the letter 'C', with the first and last control points both having surface normals pointing upwards, the ribbon should start flat, parallel to the ground, slowly turn, and then end flat again, facing the same way as the first control point. To do this "smoothly", it would have to face outwards half-way through the curve. At the moment (for this case), I've only been able to get all the surfaces facing upwards (and not outwards in the middle), which creates an ugly transition in the middle. It's quite hard to explain, I've attached some images below of this example with what it currently looks like (all surfaces facing upwards, sharp flip in the middle) and what it should look like (smooth transition, surfaces slowly rotate round). Silver faces represent the front, black faces the back. Incorrect, what it currently looks like: Correct, what it should look like: All I really need is to be able to calculate this "hybrid normal vector" for any point on the 3D cubic bézier curve, and I can generate the polygons no problem, but I can't work out how to get them to smoothly rotate round as depicted. Completely stuck as to how to proceed!

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  • I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

    - by Register Sole
    Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

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  • Given a large set of vertices in a non-convex polygon, how can i find the edges?

    - by tommy chheng
    I have a set of vertices(called A) and I want to find all the border vertices such that this border vertices set is an outline of the shape. Many of the vertices in A are redundant because they are inside the shape, I want to get rid of these vertices. My question is similar to http://stackoverflow.com/questions/477867/best-algorithm-to-find-the-edges-polygon-of-vertices but i need it to work for a non-convex polygon case.

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  • A polygon creation program, adjacent face ignoring not working right. Any solutions?

    - by user292767
    I'm working on a simple program that converts a 3d array into a polygon structure similar to voxels. It reads the array and creates cubes for positions with a value and checks adjacent directions (North,south,east,west,up,down) for a null value before setting up a cube's face. A link that displays the full code is below, written in GLBasic. Some snapshots to show you whats up. link text

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