Cycles texture interpolation issues #43779

New Issue

Hilbert Jonker · 2015-02-22T18:14:12+01:00

Hilbert Jonker commented

2015-02-22 18:14:12 +01:00

System Information
OS: Ubuntu Linux 14.04 64 bit
Graphics: nVidia GeForce GTX 560 Ti

Blender Version
Broken: 2.73a bbf09d9
(Tested with same result on 2.67 and 2.70)

Short description of error
With a transparent shader and a PNG image the first or top row and the first or left most column seems to pick the color and transparency of the row or column on the other side of the image (i.e. bottom row and right most column, respectively). An off-by-one error?

Exact steps for others to reproduce the error
See attached .blend file: Test_transparency.blend (the test image should be packed in it).

Create a plane.
Connect a mix shader with transparent BSDF (top) and diffuse BSDF (bottom) to surface.
Add a PNG image texture with transparency.
Connect image color output into diffuse shader and alpha into fac of mix shader.
UV map plane to the image - note: use complete image till border.
Look at rendered viewport or render an output image.

Note: workaround
When you do not use the top most row and the left most column of the image the transparency will work as expected.

**System Information** OS: Ubuntu Linux 14.04 64 bit Graphics: nVidia GeForce GTX 560 Ti **Blender Version** Broken: 2.73a bbf09d9 (Tested with same result on 2.67 and 2.70) **Short description of error** With a transparent shader and a PNG image the first or top row and the first or left most column seems to pick the color and transparency of the row or column on the other side of the image (i.e. bottom row and right most column, respectively). An off-by-one error? **Exact steps for others to reproduce the error** See attached .blend file: [Test_transparency.blend](https://archive.blender.org/developer/F145282/Test_transparency.blend) (the test image should be packed in it). - Create a plane. - Connect a mix shader with transparent BSDF (top) and diffuse BSDF (bottom) to surface. - Add a PNG image texture with transparency. - Connect image color output into diffuse shader and alpha into fac of mix shader. - UV map plane to the image - note: use complete image till border. - Look at rendered viewport or render an output image. **Note: workaround** When you do not use the top most row and the left most column of the image the transparency will work as expected.

Hilbert Jonker commented

2015-02-22 18:14:12 +01:00

Changed status to: 'Open'

Hilbert Jonker commented

2015-02-22 18:14:12 +01:00

Added subscriber: @hilbert

blender-admin commented

2015-02-22 18:14:12 +01:00

#43795 was marked as duplicate of this issue

Julian Eisel commented

2015-02-23 19:54:55 +01:00

Added subscriber: @JulianEisel

Julian Eisel commented

2015-02-23 19:54:55 +01:00

Can confirm that. Using viewport texture mode, everything looks fine, so maybe it's a cycles texture mapping issue? Assigning to sergey in case he gets bored with dependency graph ;)

Sergey Sharybin was assigned by Julian Eisel

2015-02-23 19:55:07 +01:00

Zauber Paracelsus commented

2015-02-24 02:42:49 +01:00

Added subscriber: @ZauberParacelsus

Zauber Paracelsus commented

2015-02-24 02:42:49 +01:00

I see it on both final render and in rendered viewport.

I think this may be a fundamental issue with texture interpolation. I've seen it in other 3D applications (such as Second Life), where if you have 1x1 repeats on a cube, you'll see some edges interpolated against the opposite side of the texture. What I usually do in those cases is set the repeats to 0.995 x 0.995. I tried that workaround on the example .blend file using the Vector->Mapping node, but it didn't work unfortunately.

Anyways, there are a couple workarounds you can use.

On the Image Texture node, go to the 2nd dropdown, and change it from Linear to Closest. Doing so will turn off smooth interpolation, so if you zoom in the pixels won't be smoothed, they'll be hard-edged. If you're only using this for big solid colors and aren't using any curved or angled shapes (much like the example image), this won't hurt anything.
Another possible workaround would be to use a higher-resolution texture, and perhaps putting a 1px thick alpha border around all sides of the image, so that there is no bleed-through.

I see it on both final render and in rendered viewport. I think this may be a fundamental issue with texture interpolation. I've seen it in other 3D applications (such as Second Life), where if you have 1x1 repeats on a cube, you'll see some edges interpolated against the opposite side of the texture. What I usually do in those cases is set the repeats to 0.995 x 0.995. I tried that workaround on the example .blend file using the Vector->Mapping node, but it didn't work unfortunately. Anyways, there are a couple workarounds you can use. 1) On the Image Texture node, go to the 2nd dropdown, and change it from Linear to Closest. Doing so will turn off smooth interpolation, so if you zoom in the pixels won't be smoothed, they'll be hard-edged. If you're only using this for big solid colors and aren't using any curved or angled shapes (much like the example image), this won't hurt anything. 2) Another possible workaround would be to use a higher-resolution texture, and perhaps putting a 1px thick alpha border around all sides of the image, so that there is no bleed-through.

Sergey Sharybin changed title from ~~Cycles transparent material~~ to Cycles texture interpolation issues

2015-02-27 08:33:08 +01:00

Sergey Sharybin commented

2015-02-27 08:33:43 +01:00

Added subscribers: @SleepyMolecule, @zeauro, @MikePan, @Sergey

Hayes commented

2015-02-27 14:25:26 +01:00

At least one person with an nVidia card is unable to reproduce (https://developer.blender.org/T43795).

In #43795#291922, @MikePan wrote:
Cannot produce error either. Both render show the 1pixel border. GPU is a GTX970 running 347.09 Driver on Win7.

I experience texture offset using OpenCL on AMD hardware.

At least one person with an nVidia card is unable to reproduce (https://developer.blender.org/T43795). > In #43795#291922, @MikePan wrote: > Cannot produce error either. Both render show the 1pixel border. GPU is a GTX970 running 347.09 Driver on Win7. I experience texture offset using OpenCL on AMD hardware.

Hayes commented

2015-02-27 15:09:21 +01:00

After playing with the transparency example and comparing the same result in the internal render, I'm inclined to say that this issue is more a lack of feature.
Exactly the same artifact appears in BI When using an Image or Movie type Texture, however under the Image Mapping section is the option Extension.
The setting Extend specifically repeats the edge pixels of the texture instead of wrapping around.
The setting Clip simply makes all pixels beyond the texture transparent.
The default setting Repeat wraps the texture, this seems the be the default behavior in cycles for any given image texture.
Using either the Extend or Clip settings immediately resolves the artifact.

Right now there is no way to change it, it seems. Having the option for Cycles Image Textures would solve this without work around's.
An interesting side note re: CPU / GPU texture offset, this example shows that the offset I am experiencing is down and left 1~ pixel, as the top line is slightly thicker and the left line is gone.
(OpenCL GPU render on r7 260x, catalyst omega 14.12)
Although these topics are merged due to visual similarity, I feel that the CPU / GPU issue might be different?

After playing with the transparency example and comparing the same result in the internal render, I'm inclined to say that this issue is more a lack of feature. Exactly the same artifact appears in BI When using an Image or Movie type Texture, however under the Image Mapping section is the option Extension. The setting Extend specifically repeats the edge pixels of the texture instead of wrapping around. The setting Clip simply makes all pixels beyond the texture transparent. The default setting Repeat wraps the texture, this seems the be the default behavior in cycles for any given image texture. Using either the Extend or Clip settings immediately resolves the artifact. Right now there is no way to change it, it seems. Having the option for Cycles Image Textures would solve this without work around's. An interesting side note re: CPU / GPU texture offset, this example shows that the offset I am experiencing is down and left 1~ pixel, as the top line is slightly thicker and the left line is gone. ![borderartifact.png](https://archive.blender.org/developer/F146105/borderartifact.png) (OpenCL GPU render on r7 260x, catalyst omega 14.12) Although these topics are merged due to visual similarity, I feel that the CPU / GPU issue might be different?

Zauber Paracelsus commented

2015-02-27 15:31:53 +01:00

I was able to repro the issue on both CPU and GPU/CUDA.

System Information
64bit Manjaro Linux, kernel 3.14.33
CPU: AMD Phenom II 970 Deneb quad-core
GPU: nVidia GTX 650 Ti, driver 346.35

I was able to repro the issue on both CPU and GPU/CUDA. **System Information** 64bit Manjaro Linux, kernel 3.14.33 CPU: AMD Phenom II 970 Deneb quad-core GPU: nVidia GTX 650 Ti, driver 346.35

Hayes commented

2015-03-01 06:37:16 +01:00

Please un-merge #43795 (Texture Offset between Cycles CPU and GPU render) as it is unrelated, thanks!

Sergey Sharybin commented

2015-03-02 08:54:04 +01:00

I'm not sure why you consider #43795 unrelated. The root of the issue is exactly the same -- wrapping coordinates on the image boundary when doing interpolation. The fact that some devices does expected interpolation in this case doesn't make any difference in the root of the issue.

blender-admin commented

2015-07-21 22:13:25 +02:00

This issue was referenced by e3461a02ac

This issue was referenced by e3461a02ac3617ee50a60601ed277b0cb65459ce

Sergey Sharybin commented

2015-07-21 22:18:46 +02:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2015-07-21 22:18:46 +02:00

blender-admin commented

2015-07-30 10:37:26 +02:00

This issue was referenced by blender/cycles@92feda3bdf

This issue was referenced by blender/cycles@92feda3bdf9f8ea512391129635906033cf1c7e6

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Cycles texture interpolation issues #43779