[SOLVED] Image Projection Shader

I know Unity has a built in image projector but I am writing my own to learn how it works.
My implementation mostly works but I am seeing some weirdness.

Essentially I have created a script attached to my projector object that creates a view and projection matrix that I pass to all the projector receiver objects, (IE. Plane_1 and Plane_2) and then have a shader that calculates where the new uvs.

So my hierarchy looks like


If I translate or rotate my Projector object, the image is projected correctly onto the planes.
If I only translate my World object, again, the the image is still projected correctly.
However if I rotate my World object, the projected image is skewed.
If a picture is worth 1000 words, a video will be worth 1,000,000 so take a look here.

My code looks like so

Code (csharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5. public class ImageProjector : MonoBehaviour
6. {
7.     public Texture ProjectionTexture = null;
8.     public GameObject[] ProjectionReceivers = null;
9.     public float Angle = 0.0f;
10.  
11.     Vector4 Vec3ToVec4(Vector3 vec3, float w)
12.     {
13.         return new Vector4(vec3.x, vec3.y, vec3.z, w);
14.     }
15.  
16.     // Use this for initialization
17.     void Start()
18.     {
19.  
20.     }
21.  
22.     // Update is called once per frame
23.     void Update()
24.     {
25.         Matrix4x4 matProj = Matrix4x4.Perspective(this.camera.fieldOfView, 1, this.camera.nearClipPlane, this.camera.farClipPlane);
26.  
27.         Matrix4x4 matView = Matrix4x4.identity;
28.         matView = Matrix4x4.TRS(Vector3.zero, this.camera.transform.rotation, Vector3.one);
29.  
30.         float x = Vector3.Dot(this.camera.transform.right,      -this.camera.transform.position);
31.         float y = Vector3.Dot(this.camera.transform.up,         -this.camera.transform.position);
32.         float z = Vector3.Dot(this.camera.transform.forward,    -this.camera.transform.position);
33.  
34.         matView.SetColumn(3, new Vector4(x, y, z, 1));
35.         matView = matView.transpose;
36.  
37.         Matrix4x4 LightViewProjMatrix = matView * matProj;
38.  
39.         if (ProjectionReceivers == null || ProjectionReceivers.Length <= 0)
40.         {
41.             return;
42.         }
43.  
44.         foreach (GameObject imageReceiver in ProjectionReceivers)
45.         {
46.             ProjectionTexture.wrapMode = TextureWrapMode.Clamp;
47.             imageReceiver.renderer.sharedMaterial.SetTexture("_ShadowMap", ProjectionTexture);
48.             imageReceiver.renderer.sharedMaterial.SetMatrix("_LightViewProj", LightViewProjMatrix);
49.             imageReceiver.renderer.sharedMaterial.SetFloat("_Angle", Angle);
50.         }
51.     }
52.  
53.     void OnDrawGizmos()
54.     {
55.         Gizmos.color = Color.red;
56.  
57.         Gizmos.DrawLine(this.camera.transform.position, this.camera.transform.position + (this.camera.transform.forward * 100.0f));
58.     }
59. }
60.  
61.  

My shader is

Code (csharp):

1.  
2. Shader"Custom/DiffuseWithShadow"
3. {
4.     Properties
5.     {
6.         _MainTex ("Main Texture", 2D) = "white" {}
7.         _ShadowMap ("Shadow Map", 2D) = "white" {}
8.         _Angle ("Angle", Float) = 0.0
9.     }
10.     SubShader
11.     {
12.         Tags { "RenderType"="Opaque" }
13.         LOD 200
14.  
15.         Pass
16.         {
17.             CGPROGRAM
18.             // Upgrade NOTE: excluded shader from OpenGL ES 2.0 because it does not contain a surface program or both vertex and fragment programs.
19.             #pragma exclude_renderers gles
20.  
21.             #pragma vertex v
22.             #pragma fragment p
23.  
24.             uniform sampler2D _MainTex;
25.             uniform sampler2D _ShadowMap;
26.             uniform float4x4 _LightViewProj;
27.             uniform float _Angle;
28.  
29.  
30.             struct VertexOut
31.             {
32.                 float4 position : POSITION;
33.                 float2 uv : TEXCOORD0;
34.                 float4 proj : TEXCOORD1;
35.             } ;
36.  
37.             VertexOut v( float4 position : POSITION, float2 uv : TEXCOORD0 )
38.             {
39.                 VertexOut OUT;
40.  
41.                 OUT.position =  mul( UNITY_MATRIX_MVP, position );
42.                 OUT.uv = uv;
43.                 OUT.proj = mul( mul( _Object2World, float4(position.xyz, 1)), _LightViewProj );
44.  
45.                 return OUT;
46.             }
47.  
48.             struct PixelOut
49.             {
50.                 float4    color : COLOR;
51.             } ;
52.  
53.             PixelOut p(VertexOut IN)
54.             {
55.                 PixelOut OUT;
56.  
57.                 float2 ndc = float2(IN.proj.x/IN.proj.w, IN.proj.y/IN.proj.w);
58.                 float2 uv = (1 + float2( ndc.x, ndc.y)) * 0.5;
59.  
60.                 float theta = _Angle*3.14159/ 180;
61.                 float2x2 matRot = float2x2( cos(theta), sin(theta),
62.                                             -sin(theta), cos(theta) );
63.                 uv = mul( uv, matRot);
64.  
65.                 float4 c = tex2D( _ShadowMap, uv );
66.  
67.                 if( uv.x < 0 || uv.y < 0 ||
68.                     uv.x > 1  || uv.y > 1 || c.a <= 0.00f )
69.                     {
70.                         c = tex2D(_MainTex, IN.uv);
71.                     }
72.  
73.                 OUT.color = c;
74.  
75.                 return OUT;
76.             }
77.  
78.             ENDCG
79.         }
80.  
81.     }
82.     FallBack"Diffuse"
83. }
84.  

Any clues as to what I might be doing wrong? Thanks!

 

Ok, so I noticed a couple of issues with my math but the issue still remains...
The following is my new update code.

Code (csharp):

1.  
2. // Update is called once per frame
3.     void Update()
4.     {
5.         Matrix4x4 matProj = Matrix4x4.Perspective(this.camera.fieldOfView, 1, this.camera.nearClipPlane, this.camera.farClipPlane);
6.  
7.         Matrix4x4 matView = Matrix4x4.identity;
8.         matView = Matrix4x4.TRS(Vector3.zero, this.camera.transform.rotation, Vector3.one);
9.  
10. // Fixed - I should transpose before setting the poition.
11.         matView = matView.transpose;
12.  
13.         float x = Vector3.Dot(this.camera.transform.right,      -this.camera.transform.position);
14.         float y = Vector3.Dot(this.camera.transform.up,         -this.camera.transform.position);
15.         float z = Vector3.Dot(this.camera.transform.forward,    -this.camera.transform.position);
16.  
17. // Fixed - This should be row and not column
18.         matView.SetRow(3, new Vector4(x, y, z, 1));
19.  
20.         Matrix4x4 LightViewProjMatrix = matView * matProj;
21.  
22.         if (ProjectionReceivers == null || ProjectionReceivers.Length <= 0)
23.         {
24.             return;
25.         }
26.  
27.         foreach (GameObject imageReceiver in ProjectionReceivers)
28.         {
29.             ProjectionTexture.wrapMode = TextureWrapMode.Clamp;
30.             imageReceiver.renderer.sharedMaterial.SetTexture("_ShadowMap", ProjectionTexture);
31.             imageReceiver.renderer.sharedMaterial.SetMatrix("_LightViewProj", LightViewProjMatrix);
32.             imageReceiver.renderer.sharedMaterial.SetFloat("_Angle", Angle);
33.         }
34.     }
35.  

 

Haha ok I was being silly. I forgot that Unity's matricies are column major so when I calculate the projector view matrix, I don't need to transpose that matrix. The following is the corrected code for anyone interested!

Code (csharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5. public class ImageProjector : MonoBehaviour
6. {
7.     public Texture ProjectionTexture = null;
8.     public GameObject[] ProjectionReceivers = null;
9.     public float Angle = 0.0f;
10.  
11.     Vector4 Vec3ToVec4(Vector3 vec3, float w)
12.     {
13.         return new Vector4(vec3.x, vec3.y, vec3.z, w);
14.     }
15.  
16.     // Use this for initialization
17.     void Start()
18.     {
19.  
20.     }
21.  
22.     // Update is called once per frame
23.     void Update()
24.     {
25.         Matrix4x4 matProj = Matrix4x4.Perspective(this.camera.fieldOfView, 1, this.camera.nearClipPlane, this.camera.farClipPlane);
26.  
27.         Matrix4x4 matView = Matrix4x4.identity;
28.         matView = Matrix4x4.TRS(Vector3.zero, this.camera.transform.rotation, Vector3.one);
29.  
30.         float x = Vector3.Dot(this.camera.transform.right,      -this.camera.transform.position);
31.         float y = Vector3.Dot(this.camera.transform.up,         -this.camera.transform.position);
32.         float z = Vector3.Dot(this.camera.transform.forward,    -this.camera.transform.position);
33.  
34.         matView.SetRow(3, new Vector4(x, y, z, 1));
35.  
36.         Matrix4x4 LightViewProjMatrix = matView * matProj;
37.  
38.         if (ProjectionReceivers == null || ProjectionReceivers.Length <= 0)
39.         {
40.             return;
41.         }
42.  
43.         foreach (GameObject imageReceiver in ProjectionReceivers)
44.         {
45.             ProjectionTexture.wrapMode = TextureWrapMode.Clamp;
46.             imageReceiver.renderer.sharedMaterial.SetTexture("_ShadowMap", ProjectionTexture);
47.             imageReceiver.renderer.sharedMaterial.SetMatrix("_LightViewProj", LightViewProjMatrix);
48.             imageReceiver.renderer.sharedMaterial.SetFloat("_Angle", Angle);
49.         }
50.     }
51.  
52.     void OnDrawGizmos()
53.     {
54.         Gizmos.color = Color.red;
55.  
56.         Gizmos.DrawLine(this.camera.transform.position, this.camera.transform.position + (this.camera.transform.forward * 100.0f));
57.     }
58. }
59.  
60.  

The final working demo!

 

if I add another image projector , i see only one is working , can you tell how to make the two image projectors work at the same time

 

You made my day is so simple! Have you ever thinked to put it in asset store?