Collision System

GEBlupiController: grid collision, 1-block step-up traversal, gravity.

Constants

kMoveSpeed = 5.5f;    // units/s
kJumpSpeed = 12.0f;   // units/s
kGravity   = 25.0f;   // units/s²
kFallLimit = -10.0f;  // terminal fall velocity
kStepLimit = 1.0f;    // max step-up height

Block Solidity

bool IsSolidAt(world, gx, gy, gz):
    if out of [0, blocksPerAxis-1] on any axis: return false  // (or handled by caller clamping)
    return !world.getBlock(gx, gy, gz).isAir()

Grid coordinates are computed via std::lround(pos + kWorldCenter), then clamped to [0, blocksPerAxis - 1].

GroundHeightAt(gx, gz)

int GroundHeightAt(world, gx, gz):
    for y from top down to 0:
        if IsSolidAt(world, gx, y, gz): return y + 1
    return 0

TryMoveAxis (per-axis horizontal step)

bool TryMoveAxis(world, axisDelta):
    targetGround = GroundHeightAt(world, targetGx, targetGz)
    if targetGround - currentFeetY <= kStepLimit:
        apply the move
        if grounded: lift Y onto targetGround   // 1-block step-up traversal
        return true
    return false   // blocked — step too high

Step(world, dx, dz, jumpPressed, dt)

Step(world, dx, dz, jumpPressed, dt):
    TryMoveAxis(world, dx along X)
    TryMoveAxis(world, dz along Z)

    if onGround_ and jumpPressed:
        velocityY_ = kJumpSpeed
    velocityY_ -= kGravity * dt
    velocityY_ = max(velocityY_, kFallLimit)
    pos.y += velocityY_ * dt

    groundY = GroundHeightAt(world, gx, gz)
    if pos.y <= groundY:
        pos.y = groundY
        velocityY_ = 0
        onGround_ = true
    else:
        onGround_ = false

What's Not Implemented

• No swimming, hazard, spring, or fan tile interaction — BlockTypes has predicate helpers for these but they aren't wired into GEBlupiController.
• No object/enemy collision — there are no objects to collide with yet.
• No AABB body — collision is a single point-column check per axis, not a swept box.

Verification

tools/VerifyBlupiMovement.cpp links only GEBlupiController.cpp (no CNA dependency) and scripts movement scenarios headlessly to verify collision behavior without a live window.