Ballistic visualization with Raycasts and DebugRenderer::AddLine

I’m writing a small piece of code to help me start with a ballistics simulator inside Urho. So far, here’s my code:

void HandleKeyDown(StringHash eventType, VariantMap& eventData)
    using namespace KeyDown;
    int key = eventData[P_KEY].GetInt();

    if (key == KEY_SPACE) {
        int feetTick = 5;
        PhysicsRaycastResult raycastResult;
        Vector3 muzzle = barrelNode->GetWorldPosition() + Vector3(2, 0, 0);
        Ray departureLine(muzzle, Vector3::FORWARD);
        scene_->GetComponent<PhysicsWorld>()->RaycastSingle(raycastResult, departureLine, feetTick, 2);
        rays.Push(std::make_tuple(departureLine, departureLine.origin_ + Vector3(feetTick, 0, 0)));

        int dropAngle = 20;
        Vector3 nextFeet(feetTick, 0, 0);
        URHO3D_LOGINFO("Drop angle: " + String(dropAngle));
        while (dropAngle > 0) {
            Ray ray(muzzle + nextFeet, Vector3::UP);
            scene_->GetComponent<PhysicsWorld>()->RaycastSingle(raycastResult, ray, feetTick, 2);
            rays.Push(std::make_tuple(ray, ray.origin_ + nextFeet));

            nextFeet.x_ += feetTick;
            dropAngle -= 10;

Rays is basically this:

PODVector<std::tuple<Ray, Vector3>> rays;

Which I use to render the lines like this:

void HandlePostRenderUpdate(StringHash eventType, VariantMap & eventData)
    auto* debug = scene_->GetComponent<DebugRenderer>();

    for (unsigned i = 0; i < rays.Size(); ++i) {
        Color color = i % 2 ? Color::YELLOW : Color::MAGENTA;
        debug->AddLine(std::get<0>(rays[i]).origin_, std::get<1>(rays[i]), color, false);

Unfortunately, since the rays never hit anything, I’m not able to get the position the ray “ended”, so I can’t AddLine to the proper angled origin (note that I’m angling the ray a little bit each time). Any ideas how I can get the “end” of a raycast without hits?

Add all the bits?

Vector3 tip{ muzzle };

for (every step)
    tip += step;

Also, since Rays have both an origin and direction, all you’d need in your tuple is a float for distance/length, instead of a Vector3.

With an origin and direction, I can’t know the end point of the raycast, therefore I’m missing the second argument to AddLine.

That would then be rayStart + rayDirection * distance. :slight_smile: