How to get the screen position in an unlit shader.

Question

Hi, I'm writing a shader in unity that isn't based on "#pragma surface surf Lambert". How do I get the current pixel screen position in the fragment program? I need it to be in pixels (not between 0 and 1 or -1 and 1). Here's my shader code:

 Shader "selectedFace"
 {
     SubShader
     {
         Pass
         {
             CGPROGRAM
             #pragma vertex vert 
             #pragma fragment frag
             float4 vert(float4 vertexPosition:POSITION):POSITION
             {
                 return mul(UNITY_MATRIX_MVP,vertexPosition);
             }
             float4 frag(void):COLOR
             {
                 //GET SCREEN POSITION HERE!!!
                 return float4(0.75,1.0,0.0,1.0);
             }
             ENDCG
         }
     }
 }

Thanks :D

Answer 1

Answer by tanoshimi · Jun 19, 2016 at 07:06 AM

Define a new member in the structure passed from your vertex to fragment shader, say, scrPos. Assign it an unused TEXCOORD semantic.

Populate it in the vertex program using the ComputeScreenPos macro:

 v2f vert(appdata_full v)
  {
      o.scrPos = ComputeScreenPos(v.pos);
      ...

And then use it as follows in the fragment shader:

  fixed4 frag(v2f i) : COLOR
  {
      float2 screenPosition = (i.scrPos.xy/i.scrPos.w);

1 Show 1 · Share

JonnyHilly · Jun 19, 2016 at 08:39 AM 0

Share

thanks Much tanoshimi !, that was almost it... just needed this to work... o.locPos=mul(UNITY_MATRIX_MVP,v.vertex); o.locPos = ComputeScreenPos(o.locPos);

How to get the screen position in an unlit shader.

1 Reply

Your answer

Welcome to Unity Answers

Follow this Question

Related Questions