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  Unit Sphere
  Submitted by



File this one under the catagory of Stupid Code Tricks. All I wanted to do was just display a bounding sphere in my engine as a debugging and visualization aid. Then I found out how much code is required just to tesselate a sphere. Here is a quick and dirty class which will allow you to produce a tesselated sphere at some point in world space and with some radius. The output tesselated sphere is a always a hard-coded 224 polygon mesh.

(View the full code entry description in the source code comments)

Currently browsing [unitsphere.zip] (2,739 bytes) - [unitsphere.h] - (1,764 bytes)

#ifndef UNITSPHERE_H

#define UNITSPHERE_H

//*** File this one under the catagory of Stupid Code Tricks. //*** All I wanted to do was just display a bounding sphere in my //*** engine as a debugging and visualization aid. Then I found out //*** how much code is required just to tesselate a sphere. Here //*** is a quick and dirty class which will allow you to produce //*** a tesselated sphere at some point in world space and with some //*** radius. The output tesselated sphere is a always a hard-coded //*** 224 polygon mesh. //*** //*** To use in your application simply inherte UnitSphereCallback and //*** provide the virtual method SphereTriangle //*** //*** To to produce the tesselated sphere simply invoke the static //*** method: //*** //*** UnitSphere::Tesselate(*this,center,radius); //*** //*** You can replace SpherePoint with whatever your own 3d point //*** representation might be. //*** //*** Submitted to FlipCode.com Code of the day on October 10, 2000 //*** by John W. Ratcliff jratcliff@verant.com and is released into //*** the public domain, for what it's worth. If somebody knows of //*** a lean mean high speed sphere tesselator please, feel free to //*** modify this code snippet and replace it with the new implementation. class SpherePoint { public: float x; float y; float z; };

class UnitSphereCallback { public: virtual void SphereTriangle(const SpherePoint &p1, const SpherePoint &p2, const SpherePoint &p3) = 0; };

class UnitSphere { public:

static void Tesselate(UnitSphereCallback &callback, const SpherePoint ¢er, float radius); private: };

#endif

Currently browsing [unitsphere.zip] (2,739 bytes) - [unitsphere.cpp] - (6,465 bytes)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include "unitsphere.h"

static float gVertices[] = { 0.0000f,0.0000f,1.0000f, 0.0000f,0.3827f,0.9239f, -0.1464f,0.3536f,0.9239f, -0.2706f,0.2706f,0.9239f, -0.3536f,0.1464f,0.9239f, -0.3827f,0.0000f,0.9239f, -0.3536f,-0.1464f,0.9239f, -0.2706f,-0.2706f,0.9239f, -0.1464f,-0.3536f,0.9239f, 0.0000f,-0.3827f,0.9239f, 0.1464f,-0.3536f,0.9239f, 0.2706f,-0.2706f,0.9239f, 0.3536f,-0.1464f,0.9239f, 0.3827f,0.0000f,0.9239f, 0.3536f,0.1464f,0.9239f, 0.2706f,0.2706f,0.9239f, 0.1464f,0.3536f,0.9239f, 0.0000f,0.7071f,0.7071f, -0.2706f,0.6533f,0.7071f, -0.5000f,0.5000f,0.7071f, -0.6533f,0.2706f,0.7071f, -0.7071f,0.0000f,0.7071f, -0.6533f,-0.2706f,0.7071f, -0.5000f,-0.5000f,0.7071f, -0.2706f,-0.6533f,0.7071f, 0.0000f,-0.7071f,0.7071f, 0.2706f,-0.6533f,0.7071f, 0.5000f,-0.5000f,0.7071f, 0.6533f,-0.2706f,0.7071f, 0.7071f,0.0000f,0.7071f, 0.6533f,0.2706f,0.7071f, 0.5000f,0.5000f,0.7071f, 0.2706f,0.6533f,0.7071f, 0.0000f,0.9239f,0.3827f, -0.3536f,0.8536f,0.3827f, -0.6533f,0.6533f,0.3827f, -0.8536f,0.3536f,0.3827f, -0.9239f,0.0000f,0.3827f, -0.8536f,-0.3536f,0.3827f, -0.6533f,-0.6533f,0.3827f, -0.3536f,-0.8536f,0.3827f, 0.0000f,-0.9239f,0.3827f, 0.3536f,-0.8536f,0.3827f, 0.6533f,-0.6533f,0.3827f, 0.8536f,-0.3536f,0.3827f, 0.9239f,0.0000f,0.3827f, 0.8536f,0.3536f,0.3827f, 0.6533f,0.6533f,0.3827f, 0.3536f,0.8536f,0.3827f, 0.0000f,1.0000f,0.0000f, -0.3827f,0.9239f,0.0000f, -0.7071f,0.7071f,0.0000f, -0.9239f,0.3827f,0.0000f, -1.0000f,0.0000f,0.0000f, -0.9239f,-0.3827f,0.0000f, -0.7071f,-0.7071f,0.0000f, -0.3827f,-0.9239f,0.0000f, 0.0000f,-1.0000f,0.0000f, 0.3827f,-0.9239f,0.0000f, 0.7071f,-0.7071f,0.0000f, 0.9239f,-0.3827f,0.0000f, 1.0000f,0.0000f,0.0000f, 0.9239f,0.3827f,0.0000f, 0.7071f,0.7071f,0.0000f, 0.3827f,0.9239f,0.0000f, 0.0000f,0.9239f,-0.3827f, -0.3536f,0.8536f,-0.3827f, -0.6533f,0.6533f,-0.3827f, -0.8536f,0.3536f,-0.3827f, -0.9239f,0.0000f,-0.3827f, -0.8536f,-0.3536f,-0.3827f, -0.6533f,-0.6533f,-0.3827f, -0.3536f,-0.8536f,-0.3827f, 0.0000f,-0.9239f,-0.3827f, 0.3536f,-0.8536f,-0.3827f, 0.6533f,-0.6533f,-0.3827f, 0.8536f,-0.3536f,-0.3827f, 0.9239f,0.0000f,-0.3827f, 0.8536f,0.3536f,-0.3827f, 0.6533f,0.6533f,-0.3827f, 0.3536f,0.8536f,-0.3827f, 0.0000f,0.7071f,-0.7071f, -0.2706f,0.6533f,-0.7071f, -0.5000f,0.5000f,-0.7071f, -0.6533f,0.2706f,-0.7071f, -0.7071f,0.0000f,-0.7071f, -0.6533f,-0.2706f,-0.7071f, -0.5000f,-0.5000f,-0.7071f, -0.2706f,-0.6533f,-0.7071f, 0.0000f,-0.7071f,-0.7071f, 0.2706f,-0.6533f,-0.7071f, 0.5000f,-0.5000f,-0.7071f, 0.6533f,-0.2706f,-0.7071f, 0.7071f,0.0000f,-0.7071f, 0.6533f,0.2706f,-0.7071f, 0.5000f,0.5000f,-0.7071f, 0.2706f,0.6533f,-0.7071f, 0.0000f,0.3827f,-0.9239f, -0.1464f,0.3536f,-0.9239f, -0.2706f,0.2706f,-0.9239f, -0.3536f,0.1464f,-0.9239f, -0.3827f,0.0000f,-0.9239f, -0.3536f,-0.1464f,-0.9239f, -0.2706f,-0.2706f,-0.9239f, -0.1464f,-0.3536f,-0.9239f, 0.0000f,-0.3827f,-0.9239f, 0.1464f,-0.3536f,-0.9239f, 0.2706f,-0.2706f,-0.9239f, 0.3536f,-0.1464f,-0.9239f, 0.3827f,0.0000f,-0.9239f, 0.3536f,0.1464f,-0.9239f, 0.2706f,0.2706f,-0.9239f, 0.1464f,0.3536f,-0.9239f, 0.0000f,0.0000f,-1.0000f };

static int gFaces[224*3] = { 0,1,2, 0,2,3, 0,3,4, 0,4,5, 0,5,6, 0,6,7, 0,7,8, 0,8,9, 0,9,10, 0,10,11, 0,11,12, 0,12,13, 0,13,14, 0,14,15, 0,15,16, 0,16,1, 1,17,18, 1,18,2, 2,18,19, 2,19,3, 3,19,20, 3,20,4, 4,20,21, 4,21,5, 5,21,22, 5,22,6, 6,22,23, 6,23,7, 7,23,24, 7,24,8, 8,24,25, 8,25,9, 9,25,26, 9,26,10, 10,26,27, 10,27,11, 11,27,28, 11,28,12, 12,28,29, 12,29,13, 13,29,30, 13,30,14, 14,30,31, 14,31,15, 15,31,32, 15,32,16, 16,32,17, 16,17,1, 17,33,34, 17,34,18, 18,34,35, 18,35,19, 19,35,36, 19,36,20, 20,36,37, 20,37,21, 21,37,38, 21,38,22, 22,38,39, 22,39,23, 23,39,40, 23,40,24, 24,40,41, 24,41,25, 25,41,42, 25,42,26, 26,42,43, 26,43,27, 27,43,44, 27,44,28, 28,44,45, 28,45,29, 29,45,46, 29,46,30, 30,46,47, 30,47,31, 31,47,48, 31,48,32, 32,48,33, 32,33,17, 33,49,50, 33,50,34, 34,50,51, 34,51,35, 35,51,52, 35,52,36, 36,52,53, 36,53,37, 37,53,54, 37,54,38, 38,54,55, 38,55,39, 39,55,56, 39,56,40, 40,56,57, 40,57,41, 41,57,58, 41,58,42, 42,58,59, 42,59,43, 43,59,60, 43,60,44, 44,60,61, 44,61,45, 45,61,62, 45,62,46, 46,62,63, 46,63,47, 47,63,64, 47,64,48, 48,64,49, 48,49,33, 49,65,66, 49,66,50, 50,66,67, 50,67,51, 51,67,68, 51,68,52, 52,68,69, 52,69,53, 53,69,70, 53,70,54, 54,70,71, 54,71,55, 55,71,72, 55,72,56, 56,72,73, 56,73,57, 57,73,74, 57,74,58, 58,74,75, 58,75,59, 59,75,76, 59,76,60, 60,76,77, 60,77,61, 61,77,78, 61,78,62, 62,78,79, 62,79,63, 63,79,80, 63,80,64, 64,80,65, 64,65,49, 65,81,82, 65,82,66, 66,82,83, 66,83,67, 67,83,84, 67,84,68, 68,84,85, 68,85,69, 69,85,86, 69,86,70, 70,86,87, 70,87,71, 71,87,88, 71,88,72, 72,88,89, 72,89,73, 73,89,90, 73,90,74, 74,90,91, 74,91,75, 75,91,92, 75,92,76, 76,92,93, 76,93,77, 77,93,94, 77,94,78, 78,94,95, 78,95,79, 79,95,96, 79,96,80, 80,96,81, 80,81,65, 81,97,98, 81,98,82, 82,98,99, 82,99,83, 83,99,100, 83,100,84, 84,100,101, 84,101,85, 85,101,102, 85,102,86, 86,102,103, 86,103,87, 87,103,104, 87,104,88, 88,104,105, 88,105,89, 89,105,106, 89,106,90, 90,106,107, 90,107,91, 91,107,108, 91,108,92, 92,108,109, 92,109,93, 93,109,110, 93,110,94, 94,110,111, 94,111,95, 95,111,112, 95,112,96, 96,112,97, 96,97,81, 113,98,97, 113,99,98, 113,100,99, 113,101,100, 113,102,101, 113,103,102, 113,104,103, 113,105,104, 113,106,105, 113,107,106, 113,108,107, 113,109,108, 113,110,109, 113,111,110, 113,112,111, 113,97,112 };

void UnitSphere::Tesselate(UnitSphereCallback &callback, const SpherePoint ¢er, float radius) { int *source = gFaces;

for (int i=0; i<224; i++) { int i1 = (*source++)*3; int i2 = (*source++)*3; int i3 = (*source++)*3;

SpherePoint p1,p2,p3;

p1.x = gVertices[i1+0] * radius + center.x; p1.y = gVertices[i1+1] * radius + center.y; p1.z = gVertices[i1+2] * radius + center.z;

p2.x = gVertices[i2+0] * radius + center.x; p2.y = gVertices[i2+1] * radius + center.y; p2.z = gVertices[i2+2] * radius + center.z;

p3.x = gVertices[i3+0] * radius + center.x; p3.y = gVertices[i3+1] * radius + center.y; p3.z = gVertices[i3+2] * radius + center.z;

callback.SphereTriangle(p1,p2,p3);

}

}


The zip file viewer built into the Developer Toolbox made use of the zlib library, as well as the zlibdll source additions.

 

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