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Asked: 2026-06-03T02:59:05+00:00

Having some issues with smooth alpha gradients in texture files resulting in bad banding

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Having some issues with smooth alpha gradients in texture files resulting in bad banding issues.

I have a 2D XNA WP7 game and I’ve come up with a fairly simple lighting system. I draw the areas that would be lit by the light in a separate RenderTarget2D, apply a sprite to dim the edges as you get further away from the light, then blend that final lighting image with the main image to make certain areas darker and lighter.

Here’s what I’ve got so far:

spotlight mask

light banding example

As you can see, the banding is pretty bad. The alpha transparency is quite smooth in the source image, but whenever I draw the sprite, it gets these huge ugly steps between colors. Just to check I drew the spotlight mask straight onto the scene with normal alpha blending and I still got the banding.

Is there any way to preserve smooth alpha gradients when drawing sprites?

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1 Answer

  1. Editorial Team

    Found out that with Mango, apps can now specify that they support 32bpp, and it will work on devices that support it!

    no light banding example

    For XNA, put this line at the top of OnNavigatedTo:

    SharedGraphicsDeviceManager.Current.PreferredBackBufferFormat = SurfaceFormat.Color;

    For Silverlight add BitsPerPixel="32" to the App element in WMAppManifest.xml.

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