Create ClippableObject.cs

Scripts/ClippableObject.cs

@@ -0,0 +1,116 @@
+using UnityEngine;
+using System.Collections;
+using System.Linq;
+
+[ExecuteInEditMode]
+public class ClippableObject : MonoBehaviour {
+    public void OnEnable() {
+        //let's just create a new material instance.
+        GetComponent<MeshRenderer>().sharedMaterial = new Material(Shader.Find("Custom/StandardClippable")) {
+            hideFlags = HideFlags.HideAndDontSave
+        };
+    }
+
+    public void Start() { }
+
+    //only 3 clip planes for now, will need to modify the shader for more.
+    [Range(0, 3)]
+    public int clipPlanes = 0;
+
+    //preview size for the planes. Shown when the object is selected.
+    public float planePreviewSize = 5.0f;
+
+    //Positions and rotations for the planes. The rotations will be converted into normals to be used by the shaders.
+    public Vector3 plane1Position = Vector3.zero;
+    public Vector3 plane1Rotation = new Vector3(0, 0, 0);
+
+    public Vector3 plane2Position = Vector3.zero;
+    public Vector3 plane2Rotation = new Vector3(0, 90, 90);
+
+    public Vector3 plane3Position = Vector3.zero;
+    public Vector3 plane3Rotation = new Vector3(0, 0, 90);
+
+    //Only used for previewing a plane. Draws diagonals and edges of a limited flat plane.
+    private void DrawPlane(Vector3 position, Vector3 euler) {
+        var forward = Quaternion.Euler(euler) * Vector3.forward;
+        var left = Quaternion.Euler(euler) * Vector3.left;
+
+        var forwardLeft = position + forward * planePreviewSize * 0.5f + left * planePreviewSize * 0.5f;
+        var forwardRight = forwardLeft - left * planePreviewSize;
+        var backRight = forwardRight - forward * planePreviewSize;
+        var backLeft = forwardLeft - forward * planePreviewSize;
+
+        Gizmos.DrawLine(position, forwardLeft);
+        Gizmos.DrawLine(position, forwardRight);
+        Gizmos.DrawLine(position, backRight);
+        Gizmos.DrawLine(position, backLeft);
+
+        Gizmos.DrawLine(forwardLeft, forwardRight);
+        Gizmos.DrawLine(forwardRight, backRight);
+        Gizmos.DrawLine(backRight, backLeft);
+        Gizmos.DrawLine(backLeft, forwardLeft);
+    }
+
+    private void OnDrawGizmosSelected() {
+        if (clipPlanes >= 1) {
+            DrawPlane(plane1Position, plane1Rotation);
+        }
+        if (clipPlanes >= 2) {
+            DrawPlane(plane2Position, plane2Rotation);
+        }
+        if (clipPlanes >= 3) {
+            DrawPlane(plane3Position, plane3Rotation);
+        }
+    }
+
+    //Ideally the planes do not need to be updated every frame, but we'll just keep the logic here for simplicity purposes.
+    public void Update()
+    {
+        var sharedMaterial = GetComponent<MeshRenderer>().sharedMaterial;
+
+        //Only should enable one keyword. If you want to enable any one of them, you actually need to disable the others. 
+        //This may be a bug...
+        switch (clipPlanes) {
+            case 0:
+                sharedMaterial.DisableKeyword("CLIP_ONE");
+                sharedMaterial.DisableKeyword("CLIP_TWO");
+                sharedMaterial.DisableKeyword("CLIP_THREE");
+                break;
+            case 1:
+                sharedMaterial.EnableKeyword("CLIP_ONE");
+                sharedMaterial.DisableKeyword("CLIP_TWO");
+                sharedMaterial.DisableKeyword("CLIP_THREE");
+                break;
+            case 2:
+                sharedMaterial.DisableKeyword("CLIP_ONE");
+                sharedMaterial.EnableKeyword("CLIP_TWO");
+                sharedMaterial.DisableKeyword("CLIP_THREE");
+                break;
+            case 3:
+                sharedMaterial.DisableKeyword("CLIP_ONE");
+                sharedMaterial.DisableKeyword("CLIP_TWO");
+                sharedMaterial.EnableKeyword("CLIP_THREE");
+                break;
+        }
+
+        //pass the planes to the shader if necessary.
+        if (clipPlanes >= 1)
+        {
+            sharedMaterial.SetVector("_planePos", plane1Position);
+            //plane normal vector is the rotated 'up' vector.
+            sharedMaterial.SetVector("_planeNorm", Quaternion.Euler(plane1Rotation) * Vector3.up);
+        }
+
+        if (clipPlanes >= 2)
+        {
+            sharedMaterial.SetVector("_planePos2", plane2Position);
+            sharedMaterial.SetVector("_planeNorm2", Quaternion.Euler(plane2Rotation) * Vector3.up);
+        }
+
+        if (clipPlanes >= 3)
+        {
+            sharedMaterial.SetVector("_planePos3", plane3Position);
+            sharedMaterial.SetVector("_planeNorm3", Quaternion.Euler(plane3Rotation) * Vector3.up);
+        }
+    }
+}