If I pass vertices to a shader between -1 and 1, with 0 being the middle of the screen.
would I be able to use those values without any modifications?
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Posted 17 November 2013 - 04:27 AM
Those are the limits in the Normalized Device Coordinates system (NDC)
If you also want UV coordinates for this, simply do:
out_texcoord = (in_vertex + vec2(1.0)) * 0.5;
note that this is only for a fullscreen quad
for anything else you will want to provide UVs as well
Posted 19 November 2013 - 12:21 AM
What are the UV quads relative to?
If I provided a quad's verticies between -1 and 1 couldn't I use them again for the UV if it's relative to the screen
or -1 and 1 if it's relative to the quad.
UVs are texture coordinates, between 0 and 1, unless the texture repeats, always
Of course there are lots of variations on how people specify these coordinates due to eg. texture atlasing.
But, what I did in my example was simply scaling the vertex coordinates [-1, 1] to [0, 1] so that you could re-use the vertex coordinates for a fullscreen quad. Those UVs represent the entire texture.
To answer your question - yes, but you still need to rescale the UVs to match the [0, 1] scale of texture coordinates.
Edited by Kaptein, 19 November 2013 - 12:22 AM.