fixed mip flipping

code/research/performance/Cargo.toml

@@ -25,7 +25,6 @@ glob = "0.3"
 failure = "0.1"
 fs_extra = "1.1"
 
-
 [[bin]]
 name = "performance"
 path = "src/main.rs"

code/research/performance/src/blit.vert

@@ -15,4 +15,9 @@ void main() {
     // We us `v_TexCoord` to generate gl_Position rather
     // than supply a vertex buffer.
     gl_Position = vec4(v_TexCoord * 2.0 - 1.0, 0.5, 1.0);
+
+    // Texture coordinates (aka. framebuffer coordinates) are inverted.
+    // We need to invert the y coordinate, other wise our texture will
+    // flip when going between mip levels.
+    gl_Position.y = -gl_Position.y;
 }