Split Texture using a Curved Line in Unity3D C#

Question

I have a texture that I want to slice into 2 parts, using a Vector2 array. I have all the Vector2 points for the curved line.

Question

How can I slice the texture into 2 parts using the curved line of points.

Alternative Solutions/Questions

How can I 'pixel' fill a Vector2[] shape to create a Texture?

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My attempts

1) Generating Vector2 points to create a square, with the top part being the curve edge. Looked promising but when I tried generating a Mesh, the points sorting was incorrect.

2) Dynamically created a Polygon2D Collider - mimicking the bottom part of the sliced texture - this had the same issue as attempt 1, the point ordering. So when convert the Collider to Mesh, it obviously had the same results as attempt

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In the picture below:

1. The red line simulates my Vector2 array
2. The gray+green square is the texture 1024 x 1024 pixels
3. The green area is the target area I want

Answer 1

This makes a mesh that is the shape you want (but with jagged edges on top), hopefully that is a step in the right direction. The Vector2 points[] array contains your red line. It should be sorted by the x coordinate, and all the numbers should be between 0 and 1. Needs a mesh filter and a mesh renderer with your texture.

using UnityEngine;

[RequireComponent(typeof(MeshFilter))]
[RequireComponent(typeof(MeshRenderer))]
public class createMesh : MonoBehaviour {

    void Start () {
        Vector2[] points = new Vector2[4];
        points [0] = new Vector2 (0, .5f);
        points [1] = new Vector2 (.33f, 1f);
        points [2] = new Vector2 (.66f, .5f);
        points [3] = new Vector2 (1, 1f);

        MeshFilter mf = GetComponent<MeshFilter> ();
        Mesh mesh = new Mesh();


        Vector3[] verticies = new Vector3[points.Length * 2];
        int[] triangles = new int[(points.Length - 1)*6];
        Vector3[] normals = new Vector3[points.Length * 2];
        Vector2[] uv = new Vector2[points.Length * 2];

        int vIndex = 0;
        int tIndex = 0;
        int nIndex = 0;
        int uvIndex = 0;

        for (int i = 0; i< points.Length; i++) {
            Vector3 topVert = points[i];
            Vector3 bottomVert = topVert;
            bottomVert.y = 0;
            verticies[vIndex++]= bottomVert;
            verticies[vIndex++]=topVert;

            //uv
            uv[uvIndex++] = bottomVert;
            uv[uvIndex++] = topVert;

            //normals
            normals[nIndex++] = -Vector3.forward;
            normals[nIndex++] = -Vector3.forward;

            if (i<points.Length - 1) {
                //triangles
                triangles[tIndex++] = (i)*2;
                triangles[tIndex++] = (i)*2+1;
                triangles[tIndex++] = (i)*2+2;
                triangles[tIndex++] = (i)*2+2;
                triangles[tIndex++] = (i)*2+1;
                triangles[tIndex++] = (i)*2+3;

            }
        }

        mesh.vertices = verticies;
        mesh.triangles = triangles;
        mesh.normals = normals;
        mesh.uv = uv;

        mf.mesh = mesh;
    }
}

Bonus: here's a way to do it just with the texture. To use this the bitmap has to be set to Advanced, with read/write enabled in the import settings. This method uses 0 to 1023 (or however large your texture is) for coordinates, and should work for numbers out of that range too.

using UnityEngine;
using System.Collections;


public class tex2d : MonoBehaviour {

    public Vector2[] points;

    void Start () {
        MeshRenderer mr;
        Texture2D t2d;
        Texture2D newTex = new Texture2D (1024, 1024);

        mr = GetComponent<MeshRenderer> ();
        t2d = mr.material.GetTexture (0) as Texture2D;
        MakeTex (points, t2d, ref newTex, 1024);
        mr.material.SetTexture (0, newTex);
    }


    void MakeTex(Vector2[] pnts, Texture2D inputTex, ref Texture2D outputTex, int size){

        Color bgcolor = new Color (1, 0, 1, 1);
        for (int i=0; i<(pnts.Length-1); i++) {
            Vector2 p1=pnts[i];
            Vector2 p2=pnts[i+1];

            //skip points that are out of range
            if ((p1.x <0 && p2.x <0) || (p1.x > size && p2.x>size)) continue;

            for (int x =(int)p1.x; x<(int)p2.x; x++) {
                if (x<0) continue;
                if (x>=size) break;

                float interpX = (x-p1.x)/(p2.x-p1.x);
                int interpY = (int) ((p2.y-p1.y)*interpX + p1.y);

                for (int y=0; y<interpY; y++) {
                    outputTex.SetPixel(x,y,inputTex.GetPixel(x,y));
                }
                for (int y= interpY; y<size; y++) {
                    outputTex.SetPixel(x,y,bgcolor);
                }

            }

        }
        outputTex.Apply ();
    }
}