Simple Cross Section Shader

Nevermind, thank you, this worked great with a bunch of wiggling to figure out the right numbers

 

I'm probably just being stupid here, but do I apply this shader to a plane in the scene which then intersects the object to be sectioned, or do I somehow apply it to the target object as an extra material? Will it work with objects with multiple submeshes and materials?

I can get the little preview-sphere in Inspector to show a section but I tried applying it as an additional material on my mesh and I'm getting no effect. Possibly more coffee is required.

 

Well, you could rip the part of the shader that performs the cut and integrate it in your shader.
It is not designed to work as a second material.

 

I see the effect in the material preview window, but not in the scene or running game view (apart from the artifacts around the edge).

 

Yup, I understand that. I suggest to either
a. write your own shader, perhaps using the one I shared as an example
b. use the shader I shared, but not in a second material

 

Just to be clear, that's just a simple sphere, not the multi-mesh object I tried first. Not a big deal though. I don't really have time to dive into the rabbit hole of shader writing just yet. I ended up buying this Asset Store package that arose from tomekkie2's earlier post. Ten bucks saves me a lot of time and his properties look easier to work with (separate plane and normal).

I'll circle back to this when I have time to tackle shaders, though. Thanks for taking the time to reply.

 

As I suspected. No, he won't post code, because he came here and then put it on the market. It appears to me that he used the slices technique (that he referenced above), and then just colored the internal faces as suggested by @Cascho01 ... just a guess though based on his image of the house shown in the asset store.

 

The nice thing about tomekkie's version is that clipping is controlled by a vector which defines the plane centerpoint, another vector that defines the clipping normal, and an offset float which moves the clipping plane along the normal. This makes it very easy to drop empty GameObjects into prefabs to use their position and orientation to define a clipping plane. Here is the Update code from the test project I wrote after buying the asset along with my notes to myself in comments. It's definitely easier to use than any of the other clipping shaders I've found.

Code (csharp):

1.     void Update ()
2.     {
3.         // Clipping offset from centerpoint along the normal.
4.         // Prefab objects have a thickness of 1 in this demo
5.         // so if the marker is at the rear edge (nearest the
6.         // camera, z=-0.5), an offset of 0.9f is 90% visible.
7.         float sectionOffset = 0.5f;
8.  
9.         // Apply the clipping materials
10.         clipper.Clip(true, prefab, instance);
11.  
12.         // The normal can be defined two ways; this demo uses the second method.
13.         // 1. set the Euler angles in a Vector3 and convert that to a Quaternion,
14.         //    then multiply the resulting rotation by a Vector3 unit direction
15.         //    which represents the normal at (0,0,0) degrees of rotation, or...
16.         // 2. leave the Euler angles at (0,0,0) which is the same thing as
17.         //    Quaternion.identity and use the transform of a gameobject that has
18.         //    been rotated to point along the desired normal.
19.         Vector4 sectionPlane = Quaternion.identity * marker.forward;
20.  
21.         // Centerpoint of clipping plane (called SectionPoint)
22.         Vector4 sectionPoint = new Vector4(marker.position.x, marker.position.y, marker.position.z, 1f);
23.  
24.         // Apply the changes
25.         clipper.SetClippingPlane(sectionPoint, sectionPlane, sectionOffset);
26.  
27.     }

 

@MV10 It is great to see that the solution you found works for you

@BioeJD If tomekkie2 created a shader that is on sale, good for him. It is not a bad thing to take an idea, polish it, sell and support it as a product. It is called innovation.

 

I never said it was a bad thing... where did you get that idea? You shouldn't be assuming I implied that at all. I just told him to not expect him to come back and help.

 

But thanks for being a snob and giving me the definition of innovation. You don't have to be condescending. Way to be supportive in the community.

 

You are welcome.

Indeed, this is what you did, after having 3 posts in total in the forums and zero contributions under this id.

 

I just purchased the cross section tool, and I'd like to be able to use it in exactly the way you're describing, @MV10. I'm a bit confused on your implementation. I'll apologize for my ignorance in advance, but how did you configure your objects with the example you gave? From what I can gather, you maybe gutted and then renamed HorizontalClippingSection to clipper, and then you have another script attached to your clipping gameGameobject, which the update function you posted is part of?

 

I'll just attach my entire test project. Probably easier than trying to write an explanation.

Edit: Apologies to @tomekkie2, this new zip doesn't include the shader you're selling.

 

Thank you very much. This is so helpful. Your code is so diligently commented!

 

I´ve done a new free to use Cross-Section Shader in Shaderforge.

 

is it possible, or has anyone made a shader where the polygons are clipped against a bounding volume, like a cube or sphere?

 

That is absolutely no problem in doing that.
Then for a sphere that would be an issue of passing the centre and radius.
A bounding volume would require more parameters like centre, size and rotation.

 

I have just made clipping against sphere in the newest update of my asset.
https://www.assetstore.unity3d.com/en/#!/content/14296
Wouldn't be much problem to add cube, box or cylinder options.

 

Is it possible to set a different colour/texture for each object's clipping plane?

eg. green for leaves, brown for trunk, grey for rocks, etc?

 

Absolutely yes. You mean something like on the image below?

 

Are you coloring the inside triangles so that complex meshes still look wonky, or are you actually capping off the discarded mesh?

 

Colouring the inside triangles with unlit color + fog, no shadows.

 

So are you creating new geometry to which we can apply a texture, or just showing the insides of the existing geometry with no shading?

 

He's not creating new geometry as far as I understood his reply to my question.

But I found a project on github the other day (https://github.com/daign/clipping-with-caps) which does exactly what we're trying to do. Does anybody know how to translate this into something working in unity? I had no luck, but I'm pretty new to shaders.

 

That sounds very interesting, and it doesn't modify any geometry as well.

This is a very clever idea and I haven't really thought that it could be made that way. This could be a very good fix when there are more clippling planes paralell or intersecting.
But - at least with this code - not for the cases with intersecting meshes. I made a short test on other mesh setup, without bothering to adjust the bounding box properly.

Clipped (+capped) meshes on the left, - originals before exporting to .dae on the right.

 

Finally I made an attempt and managed get that idea into Unity

WebGL demo link

 

That is fantastic. Did you get the stencils to work in deferred rendering?

 

Yes, I did.
It works in deferred in Editor, it works in deferred on Android, it works in deferred on standalone Windows. I suspect that on browser WebGL the camera doesn't actually switch mode from code.
The screenshot is actually taken in forward mode, because you can see the fog from scene lighting - the scene lighting fog doesn't work in deferred.
(In deferred fog can work as camera effect only - afaik)

 

@tomekkie2
Awesome.

I have an archviz project that uses deferred rendering and I haven't been able to get a stenciled plane drawn.

 

I am not a very experienced shader&rendering expert, but you can try the doc's examples here:
https://docs.unity3d.com/Manual/SL-Stencil.html and try it yourself.
Afaik there are some limitations in deferred.
I was testing these examples in editor few days ago. Now I have just looked again and the rendering path doesn't seem to have any effect in the first three spheres example, while the second example with hole shader doesn't seem to work in the deffered mode.
But stencils seems to work in my pre-update version of crossSection asset, which I am going to resubmit it in few days.
My webgl and apk demos are updated, while the asset itself not yet, new features not yet included are marked with asterisk.

 

I have just discovered an interesting postprocessing option for cross section shader.

That is just the edge effect from here:
https://www.assetstore.unity3d.com/en/#!/content/83913

I have just modified the normal depth texture to limit the effect to work on backface boundaries only.
I could be applied to any cross section shader.

I wouldn't do that without the help of bgolus, who kept on explaining all my questions in this thread: https://forum.unity3d.com/threads/d...-relative-to-camera-viewing-direction.485204/

 

Still experimenting with tweaks on clipping shaders.
Another cute effect from remaking the transparent shader.

 

Hi Tomekkie2, In this image you have used a sphere instead of a plane as the cross section. Is it easy to change the shape that is used to clip / cut away geo?

Cheers,
Peter

 

As long as your geo could be given by equation - it should be no problem.
Specifically if the geo could be approximated by ellipsoid.
If the sphere could be expressed as the collection of points, where
dot((wPos - centre)/R,(wPos - centre)/R) = 1

For the ellipsoid we would have more radiuses, assume Rx, Ry, Rz.

Instead (wPos - centre)/R we would need:

float3((wPos - centre).x/Rx, (wPos - centre).y/Ry, (wPos - centre).z/Rz)