Texture Image node with "Extend" and Math "Wrap" creating artifacts. #112559

New Issue

vincentnl · 2023-09-19T10:16:33+02:00

vincentnl commented

2023-09-19 10:16:33 +02:00

System Information
Operating system: W10 x64
Graphics card: GTX750

Blender Version
Broken: 3.6.3, c8c6f62cf3, September 11, 01:59:02,
Worked: No

If texture node use "Extend" parameter, then "Wrap" math node, it does introduce a transparent line on edges of each image repetition.

Based on attached .blend file.

Image 1:
https://i.imgur.com/ZPBLnrA.png

Image 2:
https://i.imgur.com/pc0nXiE.png

**System Information** Operating system: W10 x64 Graphics card: GTX750 **Blender Version** Broken: 3.6.3, c8c6f62cf3a3, September 11, 01:59:02, Worked: No If texture node use "Extend" parameter, then "Wrap" math node, it does introduce a transparent line on edges of each image repetition. Based on attached .blend file. Image 1: https://i.imgur.com/ZPBLnrA.png Image 2: https://i.imgur.com/pc0nXiE.png

clamp_test.7z

125 KiB

vincentnl added the

labels 2023-09-19 10:16:34 +02:00

vincentnl changed title from ~~Wrapping node with Texture "Extend" artifacts.~~ to Texture Image node with "Extend" and Math "Wrap" creating artifacts.

2023-09-19 10:17:54 +02:00

Philipp Oeser commented

2023-09-19 10:57:57 +02:00

Can confirm, Cycles seems to be better in that regard

Philipp Oeser added

and removed

labels 2023-09-19 10:58:12 +02:00

Charlie Jolly commented

2023-09-19 17:48:17 +02:00

This seems to only occur in Linear texture interpolation. It also occurs when extension is set to Repeat. Replacing Wrap with Fract also shows the issue.

This seems to only occur in `Linear` texture interpolation. It also occurs when extension is set to `Repeat`. Replacing `Wrap` with `Fract` also shows the issue.

Charlie Jolly commented

2023-09-19 18:19:13 +02:00

This solves the issue for me but I'm not an expert with GPU to know if this is a valid fix.

--- a/source/blender/gpu/shaders/material/gpu_shader_material_tex_image.glsl
+++ b/source/blender/gpu/shaders/material/gpu_shader_material_tex_image.glsl
@@ -56,7 +56,7 @@ void point_map_to_tube(vec3 vin, out vec3 vout)
 
 void node_tex_image_linear(vec3 co, sampler2D ima, out vec4 color, out float alpha)
 {
-  color = safe_color(texture(ima, co.xy));
+  color = safe_color(textureLod(ima, co.xy, 0.0));
   alpha = color.a;
 }

This solves the issue for me but I'm not an expert with GPU to know if this is a valid fix. ```Diff --- a/source/blender/gpu/shaders/material/gpu_shader_material_tex_image.glsl +++ b/source/blender/gpu/shaders/material/gpu_shader_material_tex_image.glsl @@ -56,7 +56,7 @@ void point_map_to_tube(vec3 vin, out vec3 vout) void node_tex_image_linear(vec3 co, sampler2D ima, out vec4 color, out float alpha) { - color = safe_color(texture(ima, co.xy)); + color = safe_color(textureLod(ima, co.xy, 0.0)); alpha = color.a; } ```

vincentnl commented

2023-09-20 13:35:49 +02:00

This seems to only occur in Linear texture interpolation. It also occurs when extension is set to Repeat. Replacing Wrap with Fract also shows the issue.

Yes I confirm this too.
Regarding your above mentioned fix, is it integrated in latest build?

> This seems to only occur in `Linear` texture interpolation. It also occurs when extension is set to `Repeat`. Replacing `Wrap` with `Fract` also shows the issue. Yes I confirm this too. Regarding your above mentioned fix, is it integrated in latest build?

Miguel Pozo commented

2023-09-20 19:49:31 +02:00

This is just the way texture sampling works on GPUs. You're going to see the same issue in any other real-time engine.
The Mip level is selected based on the UV delta between pixels and, in your case, the delta at the edge is the whole image.
That's the whole reason the REPEAT mode exists.

What @CharlieJolly change does is disable mip mapping, so not really a viable solution.

What you can do is go the other way around. Set the sampling to REPEAT and manually clamp the Y axis.

This is just the way texture sampling works on GPUs. You're going to see the same issue in any other real-time engine. The Mip level is selected based on the UV delta between pixels and, in your case, the delta at the edge is the whole image. That's the whole reason the `REPEAT` mode exists. What @CharlieJolly change does is disable mip mapping, so not really a viable solution. What you can do is go the other way around. Set the sampling to `REPEAT` and manually clamp the `Y` axis. ![imagen](/attachments/effb2baa-17a3-446e-8c7a-4d642aaf9ef7)

imagen.png

870 KiB

Miguel Pozo added

and removed

labels 2023-09-20 19:50:42 +02:00

Charlie Jolly commented

2023-09-20 22:37:40 +02:00

@pragma37 this can also be fixed by changing interpolation to Closest which also turns mip mapping off.

  if (tex->interpolation != SHD_INTERP_CLOSEST) {
    /* TODO(fclem): For now assume mipmap is always enabled. */
    sampler_state.filtering = GPU_SAMPLER_FILTERING_ANISOTROPIC | GPU_SAMPLER_FILTERING_LINEAR |
                              GPU_SAMPLER_FILTERING_MIPMAP;
  }

@pragma37 this can also be fixed by changing interpolation to `Closest` which also turns mip mapping off. ``` if (tex->interpolation != SHD_INTERP_CLOSEST) { /* TODO(fclem): For now assume mipmap is always enabled. */ sampler_state.filtering = GPU_SAMPLER_FILTERING_ANISOTROPIC | GPU_SAMPLER_FILTERING_LINEAR | GPU_SAMPLER_FILTERING_MIPMAP; } ```

vincentnl commented

2023-09-20 23:51:05 +02:00

This is just the way texture sampling works on GPUs. You're going to see the same issue in any other real-time engine.
The Mip level is selected based on the UV delta between pixels and, in your case, the delta at the edge is the whole image.
That's the whole reason the REPEAT mode exists.

What @CharlieJolly change does is disable mip mapping, so not really a viable solution.

What you can do is go the other way around. Set the sampling to REPEAT and manually clamp the Y axis.

No that's not clamping top and bottom sides correctly, it just repeat the same side all over.
You can see the intended look here: https://i.imgur.com/ZPBLnrA.png

Other than "closest" also "bicubic" does not show artifacts, so it's just "linear" showing this issue?

> This is just the way texture sampling works on GPUs. You're going to see the same issue in any other real-time engine. > The Mip level is selected based on the UV delta between pixels and, in your case, the delta at the edge is the whole image. > That's the whole reason the `REPEAT` mode exists. > > What @CharlieJolly change does is disable mip mapping, so not really a viable solution. > > What you can do is go the other way around. Set the sampling to `REPEAT` and manually clamp the `Y` axis. > > ![imagen](/attachments/effb2baa-17a3-446e-8c7a-4d642aaf9ef7) No that's not clamping top and bottom sides correctly, it just repeat the same side all over. You can see the intended look here: https://i.imgur.com/ZPBLnrA.png Other than "closest" also "bicubic" does not show artifacts, so it's just "linear" showing this issue?

Miguel Pozo commented

2023-09-21 15:37:49 +02:00

Just lower the clamp range.

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Texture Image node with "Extend" and Math "Wrap" creating artifacts. #112559