I want to draw the surface of a top down game using gosu's transform function like this:

However I can't figure out how to construct and use a transformation matrix and how to convert between onscreen positions and on surface positions.

However I can't figure out how to construct and use a transformation matrix and how to convert between onscreen positions and on surface positions.

You will probably have to concatenate (multiply) two matrices - one to rotate the image by 90° to make it 'fall on the ground', and another to implement a perspective transform based on Z coordinates. I am sure you can find information about both types of matrices in any book on 3D programming - there are only a handful of common matrix types, anyway. :)

Thanks I should be able to figure that out.

The general problem of conversion between screen coordinate-space positions and surface coordinate-space positions is called 'mouse picking'

Hopefully that helps you out some.

Hopefully that helps you out some.

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