How can I draw a XX pixels rect to fill a XX RenderTexture?

dsilvavini · February 10, 2013, 1:59am

Hello. I’m trying to fill a X*X RenderTexture with output of a shader. My scene has a Camera (EffectCamera script), a Plane (EffectScreenQuad script) and a RenderTexture. In EffectScreenQuad.Start() I create the plane by scratch, moving the vertices. cam is equal to the Camera which have EffectCamera script attached.

public class EffectScreenQuad : MonoBehaviour
{
	public Vector2 dimensions;
	public Camera cam;
	
	// Use this for initialization
	void Start ()
	{
        Vector3[] vertices  = new Vector3[4];
        Vector3[] normals   = new Vector3[4];
        Vector2[] uv        = new Vector2[4];
        int[] triangles 	= new int[6];
		
		//Create plane vertices that fill a dimensions.x*dimension.y pixels rect
		Vector3 lowerLeftPlaneScreenPos	= new Vector3(0,0,0);
		Vector3 lowerRightPlaneScreenPos= new Vector3(dimensions.x , 0 , 0);
		Vector3 upperLeftPlaneScreenPos = new Vector3(0 , dimensions.y , 0);
		
		Vector3 lowerLeftPlaneWorldPos  = cam.ScreenToWorldPoint(lowerLeftPlaneScreenPos);
		Vector3 lowerRightPlaneWorldPos = cam.ScreenToWorldPoint(lowerRightPlaneScreenPos);
		Vector3 upperLeftPlaneWorldPos = cam.ScreenToWorldPoint(upperLeftPlaneScreenPos);
		
        vertices[0] = lowerLeftPlaneWorldPos;
        vertices[1] = lowerRightPlaneWorldPos;
        vertices[2] = upperLeftPlaneWorldPos;
        vertices[3] = upperLeftPlaneWorldPos + lowerRightPlaneWorldPos;

        for (int i = 0; i < 4; i++)
            normals *= Vector3.back;*

uv[0] = Vector2.zero;
uv[1] = Vector2.right;
uv[2] = Vector2.up;
uv[3] = Vector2.right + Vector2.up;

triangles[0] = 0;
triangles[1] = 1;
triangles[2] = 2;
triangles[3] = 0;
triangles[4] = 2;
triangles[5] = 3;

MeshFilter mesh_filter = gameObject.GetComponent(“MeshFilter”) as MeshFilter;

```
 mesh_filter.mesh = new Mesh ();*
```

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

}*
// Update is called once per frame*
void Update () {*
}*
}
The next snippet is the shader. The commented code is what I need to return, but for now I’m just returning the uv coords, since I couldn’t debug the returned value using floating point TextureFormats.
Shader “clothInitPos” {
Properties {*
```
 _posTexSize("_posTexSize",Float)=16*
```
```
 _posOffset("_posOffset",Float)=5*
```
}*
SubShader {*
```
 Tags { "RenderType"="Opaque" }*
```
```
 Pass*
```
```
 {*
```

 	//First pass initializes position texture. To ensure all vertices being generated, a quad must be*

//drawn that fills _posTexSize*_posTexSize pixels.

```
 	CGPROGRAM*
```
```
 	#pragma target 3.0*
```
```
 	#pragma vertex vert*
```
```
 	#pragma fragment frag*
```
```
 	uniform float _posTexSize;*
```
```
 	uniform float _posOffset;*
```
```
 	struct v2f {*
```
```
 		float4 pos:POSITION;*
```
```
 		float2 uv:TEXCOORD0;*
```
```
 	};*
```
```
 	v2f vert(v2f IN)*
```
```
 	{*
```
```
 		v2f toFrag = IN;*
```
```
 		return toFrag;*
```
```
 	}*
```
```
 	float4 frag(v2f fromVert):COLOR*
```
```
 	{*
```

 		//Generate a regular grid by scaling uv coords by the number of verts and adding the position*

```
 		//offset*
```

//float2 scaledUV = fromVert.uv*_posTexSize*_posOffset;

 		//return float4(scaledUV.x , 0.0f , scaledUV.y , 1.0f);  //Grid in the y=0 plane. Alpha unused.*

 		return float4(fromVert.uv.x , 0.0f , fromVert.uv.y , 1.0f);*

```
 	}*
```
```
 	ENDCG*
```
```
 }*
```
}*
FallBack “Diffuse”*
}

I was expecting the result image to be a gradient of red and blue. In EffectCamera.OnRenderImage() I check the returned texture but a lot of pixels has the Camera background color, which makes me confuse.
public class EffectCamera : MonoBehaviour {

public Vector2 dimensions;*
public Camera cam;*
// Use this for initialization*
void Start () {*
}*
// Update is called once per frame*
void Update () {*
}*
void OnRenderImage(RenderTexture src , RenderTexture dst)*
{*

 Texture2D tex2D = new Texture2D((int)dimensions.x , (int)dimensions.y ,*

```
 	TextureFormat.ARGB32 , false);*
```

 tex2D.ReadPixels(new Rect(0 , 0 , dimensions.x , dimensions.y) , 0 , 0);*

```
 Color[] colors = tex2D.GetPixels ();*
```
```
 int dummy = 0;*
```
}*
}
Any help will be very appreciated.

dsilvavini · February 11, 2013, 4:09am

Solved the problem. Here’s the code to initialize a XX pixel plane using an orthographic camera (cam in the snippet). The cam orthographic size must be set to dimensions.x/2 and it must render to a dimensions.xdimensions.y RenderTexture (set in inspector).

using UnityEngine;
using System.Collections;

public class EffectScreenQuad : MonoBehaviour
{
	public Vector2 dimensions; //dimensions.x == dimmensions.y
	public Camera cam;
	
	// Use this for initialization
	void Start ()
	{
        Vector3[] vertices  = new Vector3[4];
        Vector3[] normals   = new Vector3[4];
        Vector2[] uv        = new Vector2[4];
        int[] triangles 	= new int[6];
		
		//Create plane vertices that fill a dimensions.x*dimension.y pixels rect
		Vector3 lowerLeftPlaneScreenPos	= new Vector3(0 , 0 , 0);
		Vector3 lowerRightPlaneScreenPos= new Vector3(dimensions.x , 0 , 0);
		Vector3 upperLeftPlaneScreenPos = new Vector3(0 , dimensions.y , 0);
		
		Vector3 lowerLeftPlaneWorldPos  = cam.ScreenToWorldPoint(lowerLeftPlaneScreenPos);
		Vector3 lowerRightPlaneWorldPos = cam.ScreenToWorldPoint(lowerRightPlaneScreenPos);
		Vector3 upperLeftPlaneWorldPos = cam.ScreenToWorldPoint(upperLeftPlaneScreenPos);
		Vector3 heightDelta = (upperLeftPlaneWorldPos - lowerLeftPlaneWorldPos)/2;
		Vector3 widthDelta = (lowerRightPlaneWorldPos - lowerLeftPlaneWorldPos)/2;
		
        vertices[0] = lowerLeftPlaneWorldPos;
        vertices[1] = lowerRightPlaneWorldPos;
        vertices[2] = upperLeftPlaneWorldPos;
        vertices[3] = heightDelta + widthDelta;
		
		Vector3 normal = Vector3.Cross(widthDelta , heightDelta);
		normal.Normalize();
        for (int i = 0; i < 4; i++)
            normals *= normal;*

uv[0] = Vector2.zero;
uv[1] = Vector2.right;
uv[2] = Vector2.up;
uv[3] = Vector2.right + Vector2.up;
//Unity3D culls counterclockwise faces…
triangles[0] = 0;
triangles[1] = 2;
triangles[2] = 1;
triangles[3] = 1;
triangles[4] = 2;
triangles[5] = 3;

MeshFilter mesh_filter = gameObject.GetComponent(“MeshFilter”) as MeshFilter;

```
 mesh_filter.mesh = new Mesh ();*
```

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

}*
// Update is called once per frame*
void Update () {*
}*
}
And this is the shader (currently returning just UV coords):
Shader “clothInitPos” {
Properties {*
```
 _posTexSize("_posTexSize",Float)=16*
```
```
 _posOffset("_posOffset",Float)=5*
```
}*
SubShader {*
```
 Tags { "RenderType"="Opaque" }*
```
```
 Pass*
```
```
 {*
```

 	//First pass initializes position texture. To ensure all vertices being generated, a quad must be*

//drawn that fills _posTexSize*_posTexSize pixels.

```
 	CGPROGRAM*
```
```
 	#pragma target 3.0*
```
```
 	#pragma vertex vert*
```
```
 	#pragma fragment frag*
```
```
 	uniform float _posTexSize;*
```
```
 	uniform float _posOffset;*
```
```
 	struct v2f {*
```
```
 		float4 pos:POSITION;*
```
```
 		float2 uv:TEXCOORD0;*
```
```
 	};*
```
```
 	v2f vert(v2f IN)*
```
```
 	{*
```
```
 		v2f toFrag;*
```

 		toFrag.pos = mul(UNITY_MATRIX_MVP, IN.pos);*

```
 		toFrag.uv = IN.uv;*
```
```
 		return toFrag;*
```
```
 	}*
```
```
 	float4 frag(v2f fromVert):COLOR*
```
```
 	{*
```

 		//Generate a regular grid by scaling uv coords by the number of verts and adding the position*

```
 		//offset*
```

//float2 scaledUV = fromVert.uv*_posTexSize*_posOffset;

 		//return float4(scaledUV.x , 0.0f , scaledUV.y , 1.0f);  //Grid in the y=0 plane. Alpha unused.*

 		return float4(fromVert.uv.x , 0.0f , fromVert.uv.y , 1.0f);*

```
 	}*
```
```
 	ENDCG*
```
```
 }*
```
}*
FallBack “Diffuse”*
}

How can I draw a X*X pixels rect to fill a X*X RenderTexture?

How can I draw a XX pixels rect to fill a XX RenderTexture?