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-rw-r--r--game/terrain2.cpp212
1 files changed, 212 insertions, 0 deletions
diff --git a/game/terrain2.cpp b/game/terrain2.cpp
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index 0000000..d1af221
--- /dev/null
+++ b/game/terrain2.cpp
@@ -0,0 +1,212 @@
+#include "terrain2.h"
+#include <fstream>
+#include <glm/gtx/intersect.hpp>
+#include <maths.h>
+
+TerrainMesh::TerrainMesh(const std::filesystem::path & input)
+{
+ size_t ncols = 0, nrows = 0, xllcorner = 0, yllcorner = 0, cellsize = 0;
+ std::map<std::string_view, size_t *> properties {
+ {"ncols", &ncols},
+ {"nrows", &nrows},
+ {"xllcorner", &xllcorner},
+ {"yllcorner", &yllcorner},
+ {"cellsize", &cellsize},
+ };
+ std::ifstream f {input};
+ while (!properties.empty()) {
+ std::string property;
+ f >> property;
+ f >> *properties.at(property);
+ properties.erase(property);
+ }
+ std::vector<VertexHandle> vertices;
+ vertices.reserve(ncols * nrows);
+ for (size_t row = 0; row < nrows; ++row) {
+ for (size_t col = 0; col < ncols; ++col) {
+ float height = 0;
+ f >> height;
+ vertices.push_back(add_vertex({xllcorner + (col * cellsize), yllcorner + (row * cellsize), height}));
+ }
+ }
+ if (!f.good()) {
+ throw std::runtime_error("Couldn't read terrain file");
+ }
+ for (size_t row = 1; row < nrows; ++row) {
+ for (size_t col = 1; col < ncols; ++col) {
+ add_face({
+ vertices[ncols * (row - 1) + (col - 1)],
+ vertices[ncols * (row - 0) + (col - 0)],
+ vertices[ncols * (row - 0) + (col - 1)],
+ });
+ add_face({
+ vertices[ncols * (row - 1) + (col - 1)],
+ vertices[ncols * (row - 1) + (col - 0)],
+ vertices[ncols * (row - 0) + (col - 0)],
+ });
+ }
+ }
+ update_face_normals();
+ update_vertex_normals();
+};
+
+OpenMesh::FaceHandle
+TerrainMesh::findPoint(glm::vec2 p) const
+{
+ return findPoint(p, *faces_begin());
+}
+
+TerrainMesh::PointFace::PointFace(const glm::vec2 p, const TerrainMesh * mesh) :
+ PointFace {p, mesh, *mesh->faces_begin()}
+{
+}
+
+TerrainMesh::PointFace::PointFace(const glm::vec2 p, const TerrainMesh * mesh, FaceHandle start) :
+ PointFace {p, mesh->findPoint(p, start)}
+{
+}
+
+TerrainMesh::FaceHandle
+TerrainMesh::PointFace::face(const TerrainMesh * mesh, FaceHandle start) const
+{
+ if (_face.is_valid()) {
+ assert(mesh->triangleContainsPoint(point, _face));
+ return _face;
+ }
+ else {
+ return (_face = mesh->findPoint(point, start));
+ }
+}
+
+TerrainMesh::FaceHandle
+TerrainMesh::PointFace::face(const TerrainMesh * mesh) const
+{
+ return face(mesh, *mesh->faces_begin());
+}
+
+namespace {
+ [[nodiscard]] constexpr inline bool
+ pointLeftOfLine(const glm::vec2 p, const glm::vec2 e1, const glm::vec2 e2)
+ {
+ return (e2.x - e1.x) * (p.y - e1.y) > (e2.y - e1.y) * (p.x - e1.x);
+ }
+
+ static_assert(pointLeftOfLine({1, 2}, {1, 1}, {2, 2}));
+ static_assert(pointLeftOfLine({2, 1}, {2, 2}, {1, 1}));
+ static_assert(pointLeftOfLine({2, 2}, {1, 2}, {2, 1}));
+ static_assert(pointLeftOfLine({1, 1}, {2, 1}, {1, 2}));
+
+ [[nodiscard]] constexpr inline bool
+ linesCross(const glm::vec2 a1, const glm::vec2 a2, const glm::vec2 b1, const glm::vec2 b2)
+ {
+ return pointLeftOfLine(a2, b1, b2) && pointLeftOfLine(a1, b2, b1) && pointLeftOfLine(b1, a1, a2)
+ && pointLeftOfLine(b2, a2, a1);
+ }
+
+ static_assert(linesCross({1, 1}, {2, 2}, {1, 2}, {2, 1}));
+}
+
+OpenMesh::FaceHandle
+TerrainMesh::findPoint(glm::vec2 p, OpenMesh::FaceHandle f) const
+{
+ ConstFaceVertexIter vertices;
+ while (f.is_valid() && !triangleContainsPoint(p, vertices = cfv_iter(f))) {
+ for (auto next = cfh_iter(f); next.is_valid(); ++next) {
+ f = opposite_face_handle(*next);
+ if (f.is_valid()) {
+ const auto e1 = point(to_vertex_handle(*next));
+ const auto e2 = point(to_vertex_handle(opposite_halfedge_handle(*next)));
+ if (pointLeftOfLine(p, e1, e2)) {
+ break;
+ }
+ }
+ f.reset();
+ }
+ }
+ return f;
+}
+
+glm::vec3
+TerrainMesh::positionAt(const PointFace & p) const
+{
+ glm::vec3 out {};
+ Triangle<3> t {this, fv_range(p.face(this))};
+ glm::intersectLineTriangle(p.point ^ 0.F, up, t[0], t[1], t[2], out);
+ return p.point ^ out[0];
+}
+
+[[nodiscard]] std::optional<glm::vec3>
+TerrainMesh::intersectRay(const Ray & ray) const
+{
+ return intersectRay(ray, findPoint(ray.start));
+}
+
+[[nodiscard]] std::optional<glm::vec3>
+TerrainMesh::intersectRay(const Ray & ray, FaceHandle face) const
+{
+ std::optional<glm::vec3> out;
+ walkUntil(PointFace {ray.start, face}, ray.start + (ray.direction * 10000.F), [&out, &ray, this](FaceHandle face) {
+ glm::vec2 bari {};
+ float dist {};
+ Triangle<3> t {this, fv_range(face)};
+ if (glm::intersectRayTriangle(ray.start, ray.direction, t[0], t[1], t[2], bari, dist)) {
+ out = t * bari;
+ return true;
+ }
+ return false;
+ });
+ return out;
+}
+
+void
+TerrainMesh::walk(const PointFace & from, const glm::vec2 to, const std::function<void(FaceHandle)> & op) const
+{
+ walkUntil(from, to, [&op](const auto & fh) {
+ op(fh);
+ return false;
+ });
+}
+
+void
+TerrainMesh::walkUntil(const PointFace & from, const glm::vec2 to, const std::function<bool(FaceHandle)> & op) const
+{
+ assert(from.face(this).is_valid()); // TODO replace with a boundary search
+ auto f = from.face(this);
+ FaceHandle previousFace;
+ while (f.is_valid() && !op(f)) {
+ for (auto next = cfh_iter(f); next.is_valid(); ++next) {
+ f = opposite_face_handle(*next);
+ if (f.is_valid() && f != previousFace) {
+ const auto e1 = point(to_vertex_handle(*next));
+ const auto e2 = point(to_vertex_handle(opposite_halfedge_handle(*next)));
+ if (linesCross(from.point, to, e1, e2)) {
+ previousFace = f;
+ break;
+ }
+ }
+ f.reset();
+ }
+ }
+}
+
+bool
+TerrainMesh::triangleContainsPoint(const glm::vec2 p, const glm::vec2 a, const glm::vec2 b, const glm::vec2 c)
+{
+ const auto det = (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
+
+ return det * ((b.x - a.x) * (p.y - a.y) - (b.y - a.y) * (p.x - a.x)) >= 0
+ && det * ((c.x - b.x) * (p.y - b.y) - (c.y - b.y) * (p.x - b.x)) >= 0
+ && det * ((a.x - c.x) * (p.y - c.y) - (a.y - c.y) * (p.x - c.x)) >= 0;
+}
+
+bool
+TerrainMesh::triangleContainsPoint(const glm::vec2 p, FaceHandle face) const
+{
+ return triangleContainsPoint(p, cfv_iter(face));
+}
+
+bool
+TerrainMesh::triangleContainsPoint(const glm::vec2 p, ConstFaceVertexIter vertices) const
+{
+ return triangleContainsPoint(p, point(*vertices++), point(*vertices++), point(*vertices++));
+}