Display Conduit inside Grasshopper c# / component

[Joriss]

Hi,

the intro:
i am trying to draw custom previews in rhino using c# (just points now, just to get started).
because i want to handle a very large amount of data i want to use an ECS (entity component system).
i have now chosen default ECS( GitHub - Doraku/DefaultEcs: Entity Component System framework aiming for syntax and usage simplicity with maximum performance for game development.), because i have gotten it to run on .net framework 4.8, all the other ones use a newer framework. (i am still running in rhino 7, because the c# component in rhino 8 is too buggy)

the problem:
i have tried to make a custom display conduit using the examples and explanation of:

mcneel/rhino-developer-samples/blob/5/rhinocommon/cs/SampleCsCommands/SampleCsGetMultiplePoints.cs

and

Display Conduits

but as soon as i build any of these to a dll i don’t see them in the viewport.
i guess this is because i am building to a .gha, which i then load into a grasshopper component, and type using… and then the namespace.
Any idea on how i can ‘activate’ this displayconduit from within a grasshopper component?

solutions i thought about
i don’t think i can use the standard grasshopper preview (/conduit) because i want to create mouse-over effects… so hover the mouse over meshes, and they get selected using a mesh-ray intersection.
Because i have a very large amount of complex data, i am using the ECS to preselect the meshes that are used for mouse-intersection detection, otherwise it would get too slow.
i have gotten the selection process working, indexing the right mesh, but previewing which mesh has been selected is what i can’t get working now.

code i tried
i don’t think it is really helpful if i paste code here, because for the display conduit i have only used the developer examples from rhino for now. nothing custom yet. but even the simplest examples like this one don’t work because i am not making a rhino plugin but want it to be loaded from grasshopper.
class MyConduit : Rhino.Display.DisplayConduit
{
protected override void CalculateBoundingBox(CalculateBoundingBoxEventArgs e)
{
base.CalculateBoundingBox(e);
var bbox = new BoundingBox();
bbox.Union(new Point3d(0, 0, 0));
e.IncludeBoundingBox(bbox);
}

protected override void PreDrawObjects(DrawEventArgs e)
{
base.PreDrawObjects(e);
e.Display.DrawPoint(new Point3d(0, 0, 0));
}
}

any help would be greatly appreciated.

[AndersDeleuran]

Before you go any deeper, are you aware of the built-in GH_Component DrawViewportMeshes and DrawViewportWires methods?

[Joriss]

Hi AndresDeleuran,

thanks for your quick reply.
Yes i have toyed around with DrawViewportWires and Meshes.
i think i cannot use it because i can only run DrawViewPortWires from a C# component, but i want the preview to be updated on mouse movements, so not only when the SolveInstance() or RunScript() methods are triggered, but as soon as a mouse callback event is recieved.

But maybe you are right, and i should try working with DrawViewPortWires a bit more. It just feels a bit strange to use grasshopper to preview the meshes when the simulation i am running lives rather independently in it’s own class, so it is not directly tied to a component. i was hoping to use the displayconduit directly because that feels like it would be faster.

the other issue i run into with DrawViewPortWires is ECS related… as the ECS scrolls through the memory looking for objects to preview, it uses Span. this type is not supported by the grasshopper C# component. so if i have a method to select and preview a mesh, that should live in its own class (in .net framework 4.8 + .net standard 2.0) and store it in a static property, so it can then be access by the C# component for visualisation.

[AndersDeleuran]

@Joriss

Yes i have toyed around with DrawViewportWires and Meshes.
i think i cannot use it because i can only run DrawViewPortWires from a C# component, but i want the preview to be updated on mouse movements, so not only when the SolveInstance() or RunScript() methods are triggered, but as soon as a mouse callback event is recieved.

While these examples are written in GHPython, they do demonstrate how to implement mouse events for dynamically drawing stuff. It might help:

GHPython Content From AECtech+ Barcelona Workshop

Hi All, I ran a short GHPython workshop at the AECtech+ event in Barcelona. I used this GitHub repository for sharing files with the workshop participants, and thought I’d share all the content here as well. Here is the workshop and content descriptions/links from the GitHub readme file: Dynamically Drawing and Reacting to Things with GHPython There is more to running GHPython components in SDK Mode than compiling plugins. We will demonstrate, explore, and combine these overlooked features th…

Should be very similar in C#, whether compiled or in a scripting component.

[Joriss]

Hey Anders Deleuran,

Thanks for the example…
looks like it will serve me well. I don’t know python, but it looks like it does what i need.

I also tested the other suggestion you made with DrawViewportMeshes, and it works great. i was under the wrong impression that this would work like a preview (turn green when component is selected). So thanks again for pointing that out.