Collision with GridMaps? (C#)

[tbadger]

Godot Version

4.3

Question

So, I’m working on a 3D Tactical RPG as my first Godot project. Using C# since I already have some experience with it, though it’s been a while since I’ve coded.

I’ve got AStar3D pathfinding and obstacle avoidance done. Now I’m trying to write a Unity-style SphereCast helper function which I’ll use for my String-Pulling algorithm. My problem is that now matter how I set up my scene or code, my SphereCast doesn’t detect my GridMap blocks.

In my MeshLibrary, each block is structured like this before exporting:

• Node3D (.GLB mesh)

  • MeshInstance3D (child of Node3D)

    • StaticBody3D (child of MeshInstance3D)

      • CollisionShape3D (child of StaticBody3D)

I’ve set Collision Layer to 1 for all my MeshLibrary blocks and for the Gridmap itself.

Here’s my helper class (I wanted to avoid instantiating it as a Node3D, but I don’t see a convenient way to access the scene’s DirectSpaceState from a static class without passing it as a parameter):

using Godot;
using Godot.Collections;

public partial class CollisionService : Node3D
{
    private PhysicsDirectSpaceState3D Space;
    private SphereShape3D Sphere;

    public override void _Ready()
    {
        Sphere = new SphereShape3D();
    }

    public override void _PhysicsProcess(double delta)
    {
        Space = GetWorld3D().DirectSpaceState;
    }

    public Array<Dictionary> SphereCast(Vector3 origin, float radius, Vector3 direction, float maxDistance, uint collisionMask)
    {
        Sphere.Radius = radius;
        var param = new PhysicsShapeQueryParameters3D();
        param.Shape = Sphere;
        param.Transform = new Transform3D(Basis.Identity, origin);
        param.CollisionMask = collisionMask;
        param.Motion = direction * maxDistance;
        param.CollideWithAreas = true;
        param.CollideWithBodies = true;
        var result = Space.IntersectShape(param);
        return result;
    }
}

In my Pathfinding class, for now I’m just checking if there are any walls on the straight line between the player’s starting tile and the destination on. But the SphereCast never reports a collision no matter where I path from/to. I’m sure all my parameters are correct, and I’m passing “(uint)1” as the collisionMask.

Honestly, the documentation on Physics Query Parameters and IntersectShape are very confusing as a beginner since there aren’t any practical examples listed for using them. I have no idea what I’m doing wrong here. Am I not using DirectSpaceState properly? Am I using the wrong Physics parameters or Intersect function? Is there some weird idiosyncrasy with GridMaps that screws with collision?

[Moreus]

@tbadger

param.Transform = new Transform3D(Basis.Identity, origin);

is The Global Transform?

[tbadger]

I’m passing Basis.Identity since I don’t want any transforms applied to the sphereshape other than the Radius, and I’m passing in a global position for “origin” which is where I want to cast from. Am I misunderstanding the purpose of param.Transform?

Someone also pointed out that I should be using CastMotion() since IntersectShape() disregards the motion vector (I didn’t notice that when reading the docs), so I’m using that instead now and still no luck.

[tbadger]

Welp, found out what I was doing wrong.

Since I was using an imported asset library for my MeshLibtary, my StaticBody > CollisionShape children weren’t being assigned to the proper MeshInstance. I had to right-click the imported Node3D and enable “Editable Children”. This exposes the MeshInstance that came with the asset pack, and its name will have yellow text. THAT’S what I needed to add my add my StaticBody > CollisionShape children to.

Then I deleted the old MeshLibrary, exported & re-imported it into my GridMap, and now my spherecast is properly detecting my level’s tiles.