test: add tests for voxel raycasting for block targeting

tests/testRaycast.cpp

@@ -0,0 +1,57 @@
+#include "testHarness.h"
+#include "vf/Raycast.h"
+
+using namespace vf;
+
+VF_TEST(raycastHitsBlockAlongNegativeZ) {
+    World world;
+    world.setBlock(0, 0, 0, Block::Stone);
+    RaycastHit hit = raycastVoxels(world, {0.5f, 0.5f, 5.5f}, {0, 0, -1}, 20.0f);
+    CHECK(hit.hit);
+    CHECK(hit.block == Vec3i(0, 0, 0));
+    CHECK(hit.normal == Vec3i(0, 0, 1));   // entered the +z face
+    CHECK_NEAR(hit.distance, 4.5f, 1e-3f);  // origin z=5.5 to the face at z=1
+}
+
+VF_TEST(raycastMissReturnsNoHit) {
+    World world;
+    world.setBlock(0, 0, 0, Block::Stone);
+    RaycastHit hit = raycastVoxels(world, {0.5f, 2.5f, 0.5f}, {0, 1, 0}, 20.0f);
+    CHECK(!hit.hit);
+}
+
+VF_TEST(raycastNormalGivesPlacementCell) {
+    World world;
+    world.setBlock(5, 0, 5, Block::Stone);
+    RaycastHit hit = raycastVoxels(world, {5.5f, 0.5f, 10.0f}, {0, 0, -1}, 20.0f);
+    CHECK(hit.hit);
+    CHECK(hit.block == Vec3i(5, 0, 5));
+    Vec3i placement = hit.block + hit.normal;
+    CHECK(placement == Vec3i(5, 0, 6));
+    CHECK(!world.solidAt(placement.x, placement.y, placement.z));
+}
+
+VF_TEST(raycastFromInsideSolidHitsImmediately) {
+    World world;
+    world.setBlock(3, 3, 3, Block::Stone);
+    RaycastHit hit = raycastVoxels(world, {3.5f, 3.5f, 3.5f}, {1, 0, 0}, 20.0f);
+    CHECK(hit.hit);
+    CHECK(hit.block == Vec3i(3, 3, 3));
+    CHECK_NEAR(hit.distance, 0.0f, 1e-6f);
+}
+
+VF_TEST(raycastRespectsMaxDistance) {
+    World world;
+    world.setBlock(0, 0, 0, Block::Stone);
+    RaycastHit hit = raycastVoxels(world, {0.5f, 0.5f, 20.0f}, {0, 0, -1}, 5.0f);
+    CHECK(!hit.hit);
+}
+
+VF_TEST(raycastDiagonalHitsExpectedFace) {
+    World world;
+    world.setBlock(4, 0, 0, Block::Stone);
+    RaycastHit hit = raycastVoxels(world, {0.5f, 0.5f, 0.5f}, {1, 0, 0}, 20.0f);
+    CHECK(hit.hit);
+    CHECK(hit.block == Vec3i(4, 0, 0));
+    CHECK(hit.normal == Vec3i(-1, 0, 0));
+}