Does unity flip images before mapping them?

Questions & Answers
1

Hi, I’m pretty new to unity and I’ve been out of graphics programming for a few years and I’m hoping someone can help with this odd problem.

I’m noticing that Textures that I import and map to a plane seem to be flipped.

I’ve created a test scene with just a camera, directional light and a plane that’s been rotated -90 about the x axis. I created a test texture:

17674-testtexture.png
17674-testtexture.png512×512 3.75 KB

I than set the texture on the material assigned to the plane and this is what was shown in the game preview:

17675-standarddiffuse.png
17675-standarddiffuse.png691×389 6.74 KB

I created a test shader that simply colors the pixel based on the texture coordinate to make sure that 0,0 is in the right spot.

Pass {
			CGPROGRAM
	
			#pragma vertex   vert
			#pragma fragment frag 
			#pragma target 3.0 
			 
	
			sampler2D _MainTex;
		
			struct vertInput {
				float4 v  : POSITION;
				float4 tc : TEXCOORD0;
			};
			
			struct fragmentInput {
				float4 p  : SV_POSITION;
				float4 tc : TEXCOORD0;
			};
	
			fragmentInput vert(vertInput vi) {
				fragmentInput fi;
				fi.p  = mul(UNITY_MATRIX_MVP, vi.v);
				fi.tc = vi.tc;
				return fi;
			}
	
			float4 frag(fragmentInput fi) : COLOR {
				float4 c = tex2D (_MainTex, fi.tc.xy);
				//return float4(c.rgb, 1.0);
				return float4(fi.tc.xy, 0, 1.0); 
			}
			
			ENDCG
		}

This shader produced an image that was black in the upper right hand corner of the plane. The only way that this could happen (that I can think of) is that the image is being flipped by the engine before being sampled.

Anyone have any ideas? Am I missing something obvious?

2

Texture coordinates go from 0,0 in the lower left corner, to 1,1 in the upper right corner.