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Texture zooming on ATI card jumpy


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#1 tupeltaja   Members   -  Reputation: 105

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Posted 02 October 2012 - 02:05 AM

Morning all,

When drawing a texture, which is zoomed in a lot (get pixelated), the texture starts jumping all around on ATI Radeon HD 4600 card. Same application with NVidia Geforce 9500 GT and some Quadro card seems to be zoomable in a lot deeper before similar glitch. Also on NVidia the jumpyness begins smoother. Window size is normal desktop, no dual screen, no fullscreen.

It seems, when drawing coordinates for texture are at about to exceed 16 bit limits, the behaviour start to occur.

Texture size 2048x1024.

When the width of draw rectangle is about 33k x 25k (varies due zooming), the jumping starts.

We use SlimDx, if that should matter, and this occurs at least on Win7 64bit.

Any quick workarounds or should we crop the image on certain zoom level when ATI cards are used?

Thank you in advance.

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#2 tupeltaja   Members   -  Reputation: 105

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Posted 02 October 2012 - 02:23 AM

Tested a bit more.. When zoomin in enough, a single texture pixel is drawn on window at size of 16x32 pixels, it won't get any larger after that. With NVidia at this level, the zooming is fine and one can zoom in more.

#3 Erik Rufelt   Crossbones+   -  Reputation: 3031

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Posted 02 October 2012 - 02:55 AM

Try changing the texture coordinate rect instead of the draw rect. So the draw rect is always the screen size but the texture coordinates form a very small rectangle in the texture.

#4 tupeltaja   Members   -  Reputation: 105

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Posted 02 October 2012 - 05:25 AM

Excellent brainworking!

Seems to work, the u,v coordinates needs some fine-tuning for the texture to be on exactly correct position.

Thank you very much!




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