How to draw a custom texture/material in polygon (square, ...)?

[PepaZapletal]

I'm trying to draw texture inside defined points (3, 4 or more points).

I found this: https://stackoverflow.com/questions/54433707/how-to-draw-a-polygon-with-sceneform-arcore and it's a good start.

Then I found this tutorial: https://catlikecoding.com/unity/tutorials/procedural-meshes/creating-a-mesh/ and updated the code from the previous post. Like this:

        val uvTopLeft = UvCoordinate(0.0f, 1.0f)
        val uvTopRight = UvCoordinate(1.0f, 1.0f)
        val uvBotLeft = UvCoordinate(0.0f, 0.0f)
        val uvBotRight = UvCoordinate(1.0f, 0.0f)
        val vertices: List<Vertex> = ArrayList(
            Arrays.asList(
                Vertex.builder().setPosition(p0).setNormal(up).setUvCoordinate(uvTopLeft).build(),
                Vertex.builder().setPosition(p1).setNormal(up).setUvCoordinate(uvTopRight).build(),
                Vertex.builder().setPosition(p2).setNormal(up).setUvCoordinate(uvBotLeft).build(),
                Vertex.builder().setPosition(p3).setNormal(up).setUvCoordinate(uvBotRight).build()
            )
        )
        val triangleIndices: MutableList<Int> = ArrayList(3)
        triangleIndices.add(0)
        triangleIndices.add(2)
        triangleIndices.add(1)
        triangleIndices.add(2)
        triangleIndices.add(3)
        triangleIndices.add(1)

Now it's draw texture inside 4 points (you have to insert points in correct order). But it's drawn as two triangles. So the common edges may not fit exactly.

Is it possible to somehow draw texture/material inside defined points in SceneView? Something like this:

Also, it's possible to rotate or zoom in/out the texture?

EDIT: Or maybe draw it as a model/object with texture?

[grassydragon]

Hi!

Is it possible to somehow draw texture/material inside defined points in SceneView?

Yes, if you are drawing a plane, you can just use the X and Z world coordinates of the points as the UV coordinates.

Also, it's possible to rotate or zoom in/out the texture?

Yes, you can apply rotation and scale to the UV coordinates.

Or maybe draw it as a model/object with texture?

In the Stack Overflow tutorial that you referenced the plane is created as an object. It may be just more difficult to apply a texture to more complex objects.

[PepaZapletal]

Hi @grassydragon ,

Thank you a lot for your answer!

Yes, if you are drawing a plane, you can just use the X and Z world coordinates of the points as the UV coordinates.

Yes, I'm drawing only a plane. Can you please write me more about this solution? I have ArrayList<AnchorNode> of points. So I have for every point worldPosition (X and Z world coordinates)

But how can I transform it to the UV coordinates? And then draw it on the surface?

I'm trying to find more info about it but documentation about ARCore/SceneForm is ... isn't :)

Can you please write me some more info? Where should I start? What methods to use?

[grassydragon]

But how can I transform it to the UV coordinates?

You can first try using them as is because the texture will repeat when you go out of bounds.

Can you please write me some more info? Where should I start? What methods to use?

You need to generate triangles using your points. For example, PlaneVisualizer generates triangles for a plane detected by ARCore, however, the plane points form a convex polygon as I remember and the approach can be different for concave polygons:

sceneform-android/core/src/main/java/com/google/ar/sceneform/rendering/PlaneVisualizer.java

Line 201 in 1476dde

private boolean updateRenderableDefinitionForPlane() {

The main goal is to find a way to generate triangles to render your polygon and the other things should be similar to the Stack Overflow code.

[PepaZapletal]

Thank you. I will look at it.

One more question: what if we limit the points to 4? (user define 4 points/anchors)

It will be 4 vertex/vertices of the polygon. Then we will draw this polygon/object. But with depth (height) of that object will be small (a few pixels) so it will look like a plane.

And then we can draw texture on it.

What do you think about it? Is it possible? Maybe it will be easier than the solution with generating triangles to render a polygon.

Is it possible in SceneView to render polygon defined by 4 vertexes?

@grassydragon

[grassydragon]

What do you think about it? Is it possible? Maybe it will be easier than the solution with generating triangles to render a polygon.

I think it isn't possible since the user defines arbitrary points and we can't modify a static object.

Is it possible in SceneView to render polygon defined by 4 vertexes?

No, there are only a cube, sphere and cylinder.

[ThomasGorisse]

Is it possible in SceneView to render polygon defined by 4 vertexes?

You have to use your own triangulation system.
I personnaly made it with Delaunay Triangulation but can't share the code freely.

[PepaZapletal]

Thank you both for the info!

@ThomasGorisse Can I buy the code from you? (Pay it as sponsorship for example.)

I will send you an email about it ok? Thank you.