RayIntersectMesh - Would this be possible?

robe · October 13, 2020, 11:56am

Hello, the wonderful community of gamma users and devvvvs,

First of all, I want to share my excitement for this new gamma release.

In the beginning, I was a bit skeptical about this new visual language,
but now, also attending the NODE Festival, I’ve to admit that this oop approach is so powerful and I can’t go back.

Straight to the point: I cannot find any RayIntersectMesh method in the gamma nor the stride repository. How can I achieve a functionality similar to Intersect(EX9 Geometry mesh) or the dx11 version?

Given a Ray and a geometry, know which mesh subset the ray is intersecting.

neuston · October 14, 2020, 2:30am

I am also interested in this topic. I will be waiting for the masters here to guide us some solutions, but I do have some idea for brain storming. Is it possible to change the mesh to SDF first, then check the intersection via raymarching? Elias’s workshop (Turning a .NET library into a VL library) in Node20 had demonstrated that how mesh was changed to sdf.

neuston · October 14, 2020, 8:24am

Btw, I have found a category off Physics under Stride in the experimental nodes …

robe · October 14, 2020, 10:33am

Hi Neuston, I’ll look in SDF, but it seems complicated an maybe heavy for calculation.

All the nodes RayIntersect…Something comes with stride in the preview version. All except the one i’m looking for and I’m not sure it would be easy to implement.

It seem that is not possible in stride. Can anyone confirm?

Looking in

github.com

stride3d/stride/blob/273dfddd462fd3746569f833e1493700c070b14d/sources/core/Stride.Core.Mathematics/CollisionHelper.cs#L370

    
      
          
          
    return Math.Max(distance, 0f);
          }
          
          
/// <summary>
          /// Determines whether there is an intersection between a <see cref="Stride.Core.Mathematics.Ray"/> and a point.
          /// </summary>
          /// <param name="ray">The ray to test.</param>
          /// <param name="point">The point to test.</param>
          /// <returns>Whether the two objects intersect.</returns>
          public static bool RayIntersectsPoint(ref Ray ray, ref Vector3 point)
          {
              //Source: RayIntersectsSphere
              //Reference: None
          
          
    Vector3 m;
              Vector3.Subtract(ref ray.Position, ref point, out m);
          
          
    //Same thing as RayIntersectsSphere except that the radius of the sphere (point)
              //is the epsilon for zero.
              float b = Vector3.Dot(m, ray.Direction);

There’s no method for intersecting a mesh. I’m also trying to understand how Stride manages subsets.
There’s an toggle merge meshes on File Model (Stride.Asset) node, but i did not manage to split not identify the subsets.

I’ll investigate more.

antokhio · October 14, 2020, 8:47pm

Suspect that it’s done on something like collision layer, and you need a collision mesh around it…

https://doc.stride3d.net/latest/en/manual/physics/raycasting.html

tonfilm · October 15, 2020, 6:29pm

Yes, antokhio is right, what you are looking for is raycasting. Unfortunately we didn’t have time to make the nodes for that yet.

What you can do if you need that now is creating a mesh collider in game studio, import it with the Asset node and reference the Stride.Physics.dll to get the raycasting methods.

See the last section of this video:

If you are looking for entity picking in the scene, like in 3d editors, that works a little bit different. The scene gets rendered with the same camera and a unique color for reach entity into an offscreen texture. Then your get the pixel that the mouse hovers and decode the entity id from that. This will soon be available in VL.Stride, we can use the same code as the game studio is uses.

robe · October 19, 2020, 9:46am

Thanks, @antokhio, Thanks @tonfilm !!!
I was taking the time to understand what you said…
Unfortunately, I did not understand completely, I need to study, I need more time. :)

I don’t know if I need an entity picking system, but…

What I would like to replicate, is that simple and effective interaction with subset mesh I get used to with Intersect(EX9.Geometry Mesh) or with the newer dx11 implementation by evvvvil.

I’m using Kinect hand tracking to orient a ray and hit the subset meshes coming from Collada Mesh.
If I can’t access to mesh subset and split into entities, it’s ok for me to export meshes one by one.

This week I’ll be trying all different approaches in VVVV gamma; if I won’t succeed, I’ll stick with VVVVbeta for this demo, but I don’t want to give up, 'cause I’m really loving gamma. This could be The new VVVVenaissance for me…

If anyone can help me and guide me to what I need to study and understand, thanks!

antokhio · October 19, 2020, 10:54am

Help > stride > HowTo Intersect Mouse with a Primitive ?

robe · October 19, 2020, 11:24am

Yes, exactly that, but not with a primitive; I need to do it with a custom mesh/meshes.

I started looking into that patch at the beginning and then figured out that in stride, maybe for performance optimization, all the collision helpers are primitive and there’s no straight way to do this like in vvvv beta with the intersect node…

antokhio · October 19, 2020, 4:46pm

Well just spend a hour trying to make it work but it seems there should be something called “Simulation” exposed and it isn’t, without it i doubt that’s possible…

robe · October 19, 2020, 5:06pm

@antokhio. Thanks for the participation! I’m guessing that in stride this stuff is different from dx9/dx11

I’ll look into dx11 shaders to better understand. I also installed Stride Engine to have a look at collision mesh and related.

Thanks again. I really appreciate.

antokhio · October 19, 2020, 7:17pm

All right 1 hour more https://www.youtube.com/watch?v=-oZLSKfcluM&feature=youtu.be&ab_channel=antokhio

Git repo https://github.com/antokhio/StrideCollider1

robe · October 20, 2020, 12:38am

Thanks a lot @antokhio!! Your commitment was unreal. And the results are exciting. Anyway this raycast subject is very complicated and I’ve to bend my mind to understand it.

Thanks for the tutorial. I did everything you pointed in the video starting from an empty patch and it works. I’ll keep you updated as I go foward.

Bye

tonfilm · October 20, 2020, 3:04pm

thanks a lot for the video, it explains everything right, only the part of retrieving the entity can be improved on. i’v made an update to the patch and it should be easier to understand now:

the changes can be found here:

antokhio · October 21, 2020, 11:19am

Well glad to share some knowledge, looking forward for this stuff to be implemented on the main lib

system · October 21, 2021, 11:19am

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joreg · June 12, 2023, 11:39am

a minimally modified Raycast node is now included as experimental with 5.3-preview
thanks again for digging through this @antokhio

and here a transcription of the necessary steps to take in game studio to make a collider shape assigned to a model (as outlined in the video):

add asset > model > 3d model: choose file
- no textures, no material, no skeleton
add asset > scene
drag Scene to MainScene
drag model to Scene
add assets > physics > convex hull
- choose the importet 3d model asset
on the 3d model entity > add component > physics > static collider
in the component go to Static Collider > Collider Shapes → add asset
- drag the Collider Shape (created in step 5) in
- this now may take a while: note the “Loading assets…” info flashing above the editor window!
to view the collider shape enable “Physics” in the editors “Grid and Gizmo” options
to refine the collider shape, select it then activate “Decomposition” → this takes time depending on your model and used parameters