Texturing problem in Grasshopper

Grasshopper Developer
1

I am trying to preview textured geometry in Grasshopper, and I am having trouble displaying objects with pixel perfect texture previews for some reason.

I used the custom preview components from several plugins (ShapeDiver and Human), and they both produce the same issue. Below you can see what I mean with the image I am using (top) and the textured result (bottom) after I display it on a planar surface with dimensions matching exactly the image:

pixelperfect1
pixelperfect11120×892 37.1 KB

pixelperfect2
pixelperfect21118×894 61.7 KB

I wrote a version of this preview to try and see if I could solve the issue myself. Here is what the C# component looks like:

private void RunScript(string path, Plane plane, ref object A, ref object outBrep)
{
  material = new Material();
  material.SetBitmapTexture(path);
  material.DiffuseColor = Color.White;
  System.Drawing.Bitmap img = new Bitmap(path);
  brep = Brep.CreateFromSurface(new PlaneSurface(plane, new Interval(0, img.Width), new Interval(0, img.Height)));
  tm = Rhino.Render.TextureMapping.CreatePlaneMapping(plane, new Interval(0, img.Width), new Interval(0, img.Height), new Interval(0, 1));
}

// <Custom additional code> 
Material material;
Brep brep;
Rhino.Render.TextureMapping tm;

//Draw all meshes in this method.
public override void DrawViewportMeshes(IGH_PreviewArgs args)
{
  Mesh[] mesh = Mesh.CreateFromBrep(brep, MeshingParameters.Default);
  mesh[0].SetTextureCoordinates(tm, Transform.Identity, true);
  args.Display.DrawMeshShaded(mesh[0], new Rhino.Display.DisplayMaterial(material));
}

It seems to work fine, except that it has the exact same discrepancy than the two plugins mentioned above. This led me to two possible guesses:

  1. Obviously, resizing an image will tamper with the pixels since the resizing algorithm will interpolate the original colors to the new dimensions. I thought that maybe my surfaces were not exactly the right dimensions. However, if I bake the surface from Grasshopper and use the image as a texture directly in Rhino, I get exactly the result I want (see top image above).
  2. Somehow, the display pipeline in Grasshopper automatically does some sort of resizing and/or compression which I have no control over. In my script above, I tried playing with all the texture parameters without success.

I appreciate any help regarding this issue.

2

Is it possible the inaccuracy happens during the conversion from BRep to Mesh?

I’d also like to mention GH doesn’t have its own display pipeline.

3

Thanks for your feeback. The same problem happens if I work with input meshes and directly apply the textures on them unfortunately.

Yes, I’m aware that Grasshopper accesses the Rhino display pipeline, I meant that somewhere along this process, the texture seems to be degraded.