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kd-11
Adept II

Strange Red-green banding on textures with AMD R9 270 (OpenGL)

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Hello,

I'm experiencing some red-green noise when using low-res textures with OpenGL using 15.5 drivers (See attached screenshot, note the green on the tarmac as well as red and green coloration on other parts). The issue is easy to recreate - Simply take a RGB8 texture, get the pixel value, multiply by a large scalor value such as 5 and store in a FP16 or FP32 buffer. Then in another pass I perform tone-mapping on the values and get the noise. The effect is lessened if I disable S3tc compression, of which I'm using the driver provided form, but it is still present, just at a higher frequency. Even simply multiplying the value by say 5 and multiplying again by 0.199 later causes the same artifacts which do not appear on intel and nvidia GPUs. Keep in mind that the intermediate values are being stored in FP textures so I did not expect this. Is this a known issue? am I going against spec somehow? OpenGL games work fine on this machine btw.

It is worth noting that replacing the textures that show the noise with a checkered pattern (black and white) somehow hides the problem. Changing the texture to a higher resolution version did not help. I have also checked the latest drivers and its still happening.

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kd-11
Adept II

Re: Strange Red-green banding on textures with AMD R9 270 (OpenGL)

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I have resolved the issue by upping the bits in an intermediary brightness buffer from RGB4 to RGB8.

Thank you.

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3 Replies
jtrudeau
Staff
Staff

Re: Strange Red-green banding on AMD R9 270 (OpenGL)

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I have white listed you, and I'll move this question to the OpenGL forum. Tagging the community manager so he's aware. pinform

Welcome!

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kd-11
Adept II

Re: Strange Red-green banding on textures with AMD R9 270 (OpenGL)

Jump to solution

I have resolved the issue by upping the bits in an intermediary brightness buffer from RGB4 to RGB8.

Thank you.

View solution in original post

jtrudeau
Staff
Staff

Re: Strange Red-green banding on textures with AMD R9 270 (OpenGL)

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Cool! I was suspecting it was a color depth issue, but I don't enough about the details of this programming model to point you at "look here." Thanks for updating! That really helps.

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