calculate proper tile position

src/map/transform.cpp

@@ -1,12 +1,27 @@
 #include <llmr/map/transform.hpp>
 
+#include <llmr/util/mat4.h>
+#include <cmath>
+#include <cstdio>
+
 using namespace llmr;
 
-transform::transform()
-    : x(0.0f),
-      y(0.0f),
-      scale(1.0f) {
 
+const double MAXEXTENT = 20037508.34;
+const double D2R = M_PI / 180.0;
+const double R2D = 180.0 / M_PI;
+const double A = 6378137;
+
+
+transform::transform()
+    :
+    width(0),
+    height(0),
+    x(0),
+    y(0),
+    angle(0.0),
+    scale(1.0) {
+    setScale(scale);
 }
 
 void transform::moveBy(double dx, double dy) {
@@ -16,6 +31,61 @@ void transform::moveBy(double dx, double dy) {
 
 void transform::scaleBy(double ds, double cx, double cy) {
     scale *= ds;
-    x = x * ds + cx * (1 - ds);
-    y = y * ds + cy * (1 - ds);
+    x = x * ds + (cx - width / 2) * (1.0 - ds);
+    y = y * ds + (cy - height / 2) * (1.0 - ds);
+}
+
+// void transform::setAngle(double _angle) {
+//     angle = _angle;
+// }
+
+void transform::setScale(double new_scale) {
+    const double factor = new_scale / scale;
+    x *= factor;
+    y *= factor;
+    scale = new_scale;
+
+    const double s = scale * size;
+    zc = s / 2;
+    Bc = s / 360;
+    Cc = s / (2 * M_PI);
+}
+
+void transform::setZoom(double zoom) {
+    setScale(pow(2.0, zoom));
+}
+
+void transform::setLonLat(double lon, double lat) {
+    const double f = fmin(fmax(sin(D2R * lat), -0.9999), 0.9999);
+    x = -round(lon * Bc);
+    y = round(0.5 * Cc * log((1 + f) / (1 - f)));
+
+    fprintf(stderr, "pos: %f/%f\n", x, y);
+}
+
+void transform::getLonLat(double& lon, double& lat) const {
+    lon = -x / Bc;
+    lat = R2D * (2 * atan(exp(y / Cc)) - 0.5 * M_PI);
+}
+
+double transform::pixel_x() const {
+    const double center = (width - scale * size) / 2;
+    return center + x;
+}
+
+double transform::pixel_y() const {
+    const double center = (height - scale * size) / 2;
+    return center + y;
+}
+
+void transform::matrixFor(float matrix[16], uint32_t tile_z, uint32_t tile_x, uint32_t tile_y) const {
+    const double tile_scale = pow(2, tile_z);
+    const double tile_size = scale * size / tile_scale;
+
+    mat4_identity(matrix);
+    mat4_translate(matrix, matrix, pixel_x(), pixel_y(), -1);
+    mat4_translate(matrix, matrix, tile_x * tile_size, tile_y * tile_size, 0);
+
+    // TODO: Get rid of the 8 (scaling from 4096 to 512 px tile size);
+    mat4_scale(matrix, matrix, scale / tile_scale / 8, scale / tile_scale / 8, 1);
 }