Question How to fit a texture to a mesh?

I am capturing a screenshot from my camera

I now want to display this screenshot on a mesh

But I want it to fit it so the mesh displays only the area of the screen it was overlapping with on the camera view

So far I have the screenshot, I sample the texture in a shader, and I assign the material to the mesh renderer

However the screenshot is crammed to fit inside the shape of the mesh ( I dont know where to go from here )

Here is an image of where I am:

I assume I have to make some calculation to figure out the aspect ratio of the mesh and how much space the mesh is taking onscreen?(position, scale and distance to camera??)

And then somehow I have to send these calculations to the shader to correctly tile the texture on the mesh?

But I dont know how I can do this

Any help would be appreciated, thanks

 

Particularly I only know how to edit this in Blender, but in Unity a simple(not precise) way, would be to modify the materials offsets. As you can set cut level, and offset to a particular section of the original image. But this doesn't work well if needing many parts of said image as you'd have to make a material for each different object to render it.

I think there is a way to set UVs with code, in Unity, but sounds complicated

 

So I have a tiling and offset node that can kind of rescale the texture by plugging it in the UV of the sample texture 2D

But how do I calculate the UV coordinates of a region? How do I get a region from the position and scale of a mesh relative to a camera?

Right now what I have is a screenshot - 1920x1080 (16:9)
When I place this in a material its crammed in as I said above

I dont think I need to make many materials since I can use material property blocks? If I need multiple meshes

PS: I do think I will need scripting for this no?

 

pls no why move the thread around

I just need math, how can I find the rect of the screen a mesh is occupying
OR
how can i find the UV needed

I dont need shader graph at all, it was just an idea

 

I guess I was unclear on my original post?

I have a mesh, that mesh is a plane inside the view of the camera

I want to take a screenshot of my camera view

And I want to render that screenshot on the mesh

BUT ONLY THE EXACT PART THAT WOULD LINE UP WITH THE MESH
(at the moment when i put it in a material it just crams in the whole screen)

Basically - Crop the screen based on the mesh, and display the cropped area on the mesh.

heres my diagram again


You told me set UVs, but I have no clue what you mean.

Can you explain in more detail how setting UVs would solve my issue?

If any point is unclear please let me know, I will try again to explain sorry

 

You have given me the API to set UVs, but you didnt say what parameters I should input to get my desired result

Code (CSharp):

1. Mesh.SetUVs(???,???);

what to put in ??? to get the window that corresponds to the mesh

 

well that was the whole point of the post, there must be some math that works for any size mesh and gets the corresponding UVs. If you dont know what to put in the UVs they i know even less.

Should I make a new thread, this time dedicated on finding the UV values?

 

you are not obliged to give me a tutorial but Im thankful for it nonentheless

Im sure that given a position of a rectangular area inside of the view of the camera there must be some way of get its rect in screen space, I feel like it involves a lot of math and code to find it

 

So are you trying to make this work specifically for a rectangular mesh that is always facing the screen? Or is this something that needs to be more general and work for any mesh that could exist in 3D space? Also, is the screenshot taken of the full screen or just some part of it? Depending on your answer this can range from pretty simple to pretty complex

 

-Mesh always facing the screen

- The only part I really need of the screen is the part that is going to be displaying in the mesh
(anyway its always going to be the region occupied by the mesh in the camera view.)

The mesh is always a rectangle, but it might change position and sometimes have different scale to be a square/ or wider than it is tall, or be on a different position on the screen

thanks

 

In that case you have it really really easy. Just get the screen position of each vert in the quad and convert it to a percentage of the screen's size. That is your UV coord for that vertex.

Off the top of my head some pseudo code would be something like:

Code (CSharp):

1.  
2. Camera camera;
3. var trans = QuadObject.transform;
4. var filter = QuadObject.GetComponent<MeshFilter>();
5. var mesh = filter.mesh //or use sharedMesh if that is more appropriate in this case
6. var verts = mesh.verticies;
7. var uvs = new Vector2[verts.length];
8.  
9. for(int i = 0; i < verts.Length; i++)
10. {
11.     //transform the vert to world space, then screen space in pixels, then finally a percentage of the screen's space in pixels.
12.     var worldVert = transform.TransformPoint(verts[i]);
13.     var screenVert = camera.WorldToScreenPoint(worldVert);
14.     uvs[i] = new Vector2(
15.         screenVert.x / camera.pixelWidth,
16.         screenVert.y / camera.pixelHeight
17.         );
18. }
19.  
20. //assign calculated uvs back to the mesh
21. mesh.uv = uvs;

This code might not be 110% right. It's been a while since I had to do any mesh manipulation so I might have gotten some details wrong or the direction of the UVs might be flipped but it should get your started. heck, it might even work on the first try!