`Renderer.RenderTo` results in y-inverted image with Android

[austinbhale]

`Renderer.RenderTo` results in y-inverted image with Android

[maluoi]

This is a known issue, and very much because of GL, but I haven't really settled on a "correct" fix for it! I've kinda wondered if maybe this could be fixed by flipping the projection matrix in specific cases, or perhaps some GL extension that might be common. I'd be open to suggestions! It's kinda one of those can of worms sort of issues though.

In general at the moment, I do something like flip UVs or mesh on Android platforms. When reading color data, I also read it out bottom-to-top as well.

[austinbhale]

Ohh I guessed SK standardized top-down textures for retrieving color data. Reading just like GL gives it sounds like less surprises to me :D For this scenario, flipping the projection matrix is perfect, thanks for the tip! Something like:

perspectiveMatrix = Matrix.Perspective(fov, (float)_width / _height, 0.01f, 100);
if (Backend.Graphics is BackendGraphics.OpenGL_GLX or BackendGraphics.OpenGL_WGL or BackendGraphics.OpenGLES_EGL)
{
    Matrix flipY = new(
        1, 0, 0, 0,
        0, -1, 0, 0,
        0, 0, 1, 0,
        0, 0, 0, 1
    );
    perspectiveMatrix *= flipY;
}