Project a render texure onto a 2d plane

Hi, I am fairly new to Shaders, so bear with me please.

In my scene I have 2d objects. I want to take an existing render texture and project it directly onto those planes so that the render texture only shows where those objects are.

So far I have failed to get the coordinates for the objects properly. I have access to the render texture, but it shows up squished and in the completely wrong space. I would show you code, but it's such a mess due to me not knowing what I'm doing that it would be better to start from scratch.

My searches have not turned up anything that would help me (that I can comprehend at this point).

Thanks

 

You want screen space UVs.

Code (csharp):

1. struct v2f {
2.     // other stuff, like the pos and uv
3.  
4.     // use a number for the TEXCOORD# that isn't already used
5.     float4 projPos : TEXCOORD4;
6. };
7.  
8. // in the vertex function
9. o.projPos = ComputeScreenPos (o.vertex);
10.  
11. // in the fragment shader
12. float2 screenUV = i.projPos.xy / i.projPos.w;
13. fixed4 myColor = tex2D(_MyRenderTexture, screenUV);

 

Thank you so much! I knew it something small eluding me. It works beautifully now.