Rework collision. Possibly fixes #19

1 files changed, 64 insertions, 0 deletions

diff --git a/src/game/shared/world/ray_aabb.cc b/src/game/shared/world/ray_aabb.cc
new file mode 100644
index 0000000..f6f2638
--- /dev/null
+++ b/src/game/shared/world/ray_aabb.cc
@@ -0,0 +1,64 @@
+#include "shared/pch.hh"
+
+#include "shared/world/ray_aabb.hh"
+
+RayAABB::RayAABB(const glm::fvec3& start, const glm::fvec3& dir) noexcept
+{
+    reset(start, dir);
+}
+
+void RayAABB::reset(const glm::fvec3& start, const glm::fvec3& dir) noexcept
+{
+    assert(std::isfinite(start.x));
+    assert(std::isfinite(start.y));
+    assert(std::isfinite(start.z));
+    assert(std::isfinite(dir.x));
+    assert(std::isfinite(dir.y));
+    assert(std::isfinite(dir.z));
+
+    m_start_pos = start;
+    m_direction = dir;
+}
+
+bool RayAABB::intersect(const math::AABBf& aabb, float& distance, glm::fvec3& surface) const noexcept
+{
+    // Adapted from https://github.com/gdbooks/3DCollisions/blob/master/Chapter3/raycast_aabb.md
+
+    constexpr static std::array<glm::fvec3, 6> TNORMALS = {
+        glm::fvec3(-1.0f, 0.0f, 0.0f),
+        glm::fvec3(1.0f, 0.0f, 0.0f),
+        glm::fvec3(0.0f, -1.0f, 0.0f),
+        glm::fvec3(0.0f, 1.0f, 0.0f),
+        glm::fvec3(0.0f, 0.0f, -1.0f),
+        glm::fvec3(0.0f, 0.0f, 1.0f),
+    };
+
+    std::array<float, 6> tvalues;
+    tvalues[0] = (aabb.min.x - m_start_pos.x) / m_direction.x;
+    tvalues[1] = (aabb.max.x - m_start_pos.x) / m_direction.x;
+    tvalues[2] = (aabb.min.y - m_start_pos.y) / m_direction.y;
+    tvalues[3] = (aabb.max.y - m_start_pos.y) / m_direction.y;
+    tvalues[4] = (aabb.min.z - m_start_pos.z) / m_direction.z;
+    tvalues[5] = (aabb.max.z - m_start_pos.z) / m_direction.z;
+
+    static_assert(tvalues.size() == TNORMALS.size());
+
+    auto tmin = std::max(std::max(std::min(tvalues[0], tvalues[1]), std::min(tvalues[2], tvalues[3])), std::min(tvalues[4], tvalues[5]));
+    auto tmax = std::min(std::min(std::max(tvalues[0], tvalues[1]), std::max(tvalues[2], tvalues[3])), std::max(tvalues[4], tvalues[5]));
+
+    if(tmax < 0.0f || tmin > tmax) {
+        distance = std::numeric_limits<float>::quiet_NaN();
+        return false; // no intersection
+    }
+
+    for(std::size_t i = 0U; i < tvalues.size(); ++i) {
+        if(tvalues[i] == tmin) {
+            surface = TNORMALS[i];
+            break;
+        }
+    }
+
+    distance = tmin < 0.0f ? tmax : tmin;
+
+    return true;
+}