An abstract projection class and child mercprojection class

core/mapTile/mapTile.h

@@ -19,9 +19,6 @@ class MapTile {
     //Helper Functions
     bool setVBO(std::vector<float> _vboData);
     glm::vec2 GetBoundingBox();
-    //Maybe these should be moved 2 functions to sceneDefinition
-    glm::vec3 MercToPix();
-    glm::vec2 MercToLatLong();
     ~MapTile() {
         m_Vertices.clear();
     }

core/util/projection.cpp

@@ -0,0 +1,80 @@
+#include <cmath>
+
+#include "projection.h"
+
+
+//Constructor for MercProjection
+MercProjection::MercProjection(ProjectionType _type, int _tileSize) : MapProjection(_type), m_TileSize(_tileSize) {
+    float invTileSize = 1.0/m_TileSize;
+    m_Res = 2.0 * HALF_CIRCUMFERENCE * invTileSize;
+}
+
+glm::vec2 MercProjection::LatLonToMeters(glm::vec2 _latLon) {
+    glm::vec2 meters;
+    float inv180 = 1.0/180.0;
+    float inv360 = 1.0/360.0;
+    //Lon -> origin shift, as parallel lines
+    meters.x = _latLon.y * HALF_CIRCUMFERENCE * inv180;
+    //Lat -> first do scaling as per mercator then origin shift
+    meters.y = glm::log( glm::tan(90.0 + _latLon.x) * PI * inv360) * PI * inv180;
+    meters.y = meters.y * HALF_CIRCUMFERENCE * inv180;
+    return meters;
+}
+
+glm::vec2 MercProjection::MetersToLatLon(glm::vec2 _meters) {
+    glm::vec2 latLon;
+    float invHalfCircum = 1.0/HALF_CIRCUMFERENCE;
+    float inv180 = 1.0/180.0;
+    float invPI = 1.0/PI;
+    latLon.y = _meters.x * invHalfCircum * 180.0;
+    latLon.x = _meters.y * invHalfCircum * 180.0;
+    latLon.x = 180.0 * invPI * (2.0 * glm::atan( glm::exp(latLon.x * PI * inv180) ) - PI * 0.5);
+    return latLon;
+}
+
+glm::vec2 MercProjection::PixelsToMeters(glm::vec2 _pix, int _zoom) {
+    glm::vec2 meters;
+    // resolution: meters/pixel for a given zoom level
+    float res = m_Res * pow(2, -_zoom);
+    meters.x = _pix.x * res - HALF_CIRCUMFERENCE;
+    meters.y = _pix.y * res - HALF_CIRCUMFERENCE;
+    return meters;
+}
+
+glm::vec2 MercProjection::MetersToPixel(glm::vec2 _meters, int _zoom) {
+    glm::vec2 pix;
+    float res = m_Res * pow(2, -_zoom);
+    float invRes = 1.0/res;
+    pix.x = ( _meters.x + HALF_CIRCUMFERENCE ) * invRes;
+    pix.y = ( _meters.y + HALF_CIRCUMFERENCE ) * invRes;
+    return pix;
+}
+
+glm::ivec2 MercProjection::PixelsToTileXY(glm::vec2 _pix) {
+    //returns the tile covering a region of a pixel
+    glm::ivec2 tileXY;
+    float invTileSize = 1.0/m_TileSize;
+    tileXY.x = int(glm::ceil( _pix.x * invTileSize) - 1);
+    tileXY.y = int(glm::ceil( _pix.y * invTileSize) - 1);
+    return tileXY;
+}
+
+glm::ivec2 MercProjection::MetersToTileXY(glm::vec2 _meters, int _zoom) {
+    return PixelsToTileXY( MetersToPixel(_meters, _zoom));
+}
+
+glm::vec4 MercProjection::TileBounds(glm::ivec3 _tileCoord) {
+    glm::vec2 boundMin, boundMax;
+    boundMin = PixelsToMeters( glm::vec2(_tileCoord.x*m_TileSize, _tileCoord.y*m_TileSize), _tileCoord.z);
+    boundMax = PixelsToMeters( glm::vec2((_tileCoord.x+1)*m_TileSize, (_tileCoord.y+1)*m_TileSize), _tileCoord.z);
+    return glm::vec4(boundMin.x, boundMin.y, boundMax.x, boundMax.y);
+}
+
+glm::vec4 MercProjection::TileLatLonBounds(glm::ivec3 _tileCoord) {
+    glm::vec4 bounds = TileBounds(_tileCoord);
+    glm::vec2 minBound, maxBound;
+    minBound = MetersToLatLon(glm::vec2(bounds.x, bounds.y));
+    maxBound = MetersToLatLon(glm::vec2(bounds.z, bounds.w));
+    return glm::vec4(minBound.x, minBound.y, maxBound.x, maxBound.y);
+}
+

core/util/projection.h

@@ -0,0 +1,51 @@
+#pragma one
+
+//Define global constants
+#define PI 3.1415926535
+#define HALF_CIRCUMFERENCE 20037508.342789244
+
+#include "glm/glm.hpp"
+
+const glm::vec2 ORIGIN(HALF_CIRCUMFERENCE, HALF_CIRCUMFERENCE);
+
+enum class ProjectionType {
+    mercator
+};
+
+class MapProjection {
+protected:
+    /* m_type: type of map projection: example: mercator*/
+    ProjectionType m_type;
+public:
+    MapProjection(ProjectionType _type) : m_type(_type) {};
+    virtual glm::vec2 LatLonToMeters(glm::vec2 _latLon) = 0;
+    virtual glm::vec2 MetersToLatLon(glm::vec2 _meters) = 0;
+    virtual glm::vec2 PixelsToMeters(glm::vec2 _pix, int _zoom) = 0;
+    virtual glm::vec2 MetersToPixel(glm::vec2 _meters, int _zoom) = 0;
+    virtual glm::ivec2 PixelsToTileXY(glm::vec2 _pix) = 0;
+    virtual glm::ivec2 MetersToTileXY(glm::vec2 _meters, int _zoom) = 0;
+    virtual glm::vec4 TileBounds(glm::ivec3 _tileCoord) = 0;
+    virtual glm::vec4 TileLatLonBounds(glm::ivec3 _tileCoord) = 0;
+    virtual ProjectionType GetMapProjectionType() {return m_type;}
+    virtual ~MapProjection() {}
+};
+
+class MercProjection : public MapProjection {
+    /* 
+     * Following define the boundry covered by this mercator projection
+     */
+    float m_TileSize;
+    float m_Res;
+public:
+    MercProjection(ProjectionType _type, int  _tileSize=256);
+    virtual glm::vec2 LatLonToMeters(glm::vec2 _latLon);
+    virtual glm::vec2 MetersToLatLon(glm::vec2 _meters);
+    virtual glm::vec2 PixelsToMeters(glm::vec2 _pix, int _zoom);
+    virtual glm::vec2 MetersToPixel(glm::vec2 _meters, int _zoom);
+    virtual glm::ivec2 PixelsToTileXY(glm::vec2 _pix);
+    virtual glm::ivec2 MetersToTileXY(glm::vec2 _meters, int _zoom);
+    virtual glm::vec4 TileBounds(glm::ivec3 _tileCoord);
+    virtual glm::vec4 TileLatLonBounds(glm::ivec3 _tileCoord);
+    virtual ~MercProjection() {}
+};
+