Regression: 3D shader 3D_POLYLINE_UNIFORM_COLOR draw error (the need to set all shader uniforms need to be documented) #103176

New Issue

EMM · 2022-12-13T05:03:56+01:00

EMM commented

2022-12-13 05:03:56 +01:00

System Information
Operating system: Windows-10-10.0.22000-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3070 Laptop GPU/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 526.98

Blender Version
Broken: version: 3.1.1, 3.5
Worked: 3.1.0

Behaviour changed in blender/blender@49fc4449e7

Short description of error
draw shader error

It's normal:
Exact steps for others to reproduce the error
Run the following code block and use the move gizmo. Drag or directly draw errors

import bpy
import gpu
from gpu_extras.batch import batch_for_shader

coords = [(1, 1, 1), (-2, 0, 0), (-2, -1, 3), (0, 1, 1)]
shader = gpu.shader.from_builtin('3D_POLYLINE_UNIFORM_COLOR')
batch = batch_for_shader(shader, 'LINES', {"pos": coords})


def draw():
    shader.uniform_float("color", (1, 1, 0, 1))
    batch.draw(shader)


bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW')

**System Information** Operating system: Windows-10-10.0.22000-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3070 Laptop GPU/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 526.98 **Blender Version** Broken: version: 3.1.1, 3.5 Worked: 3.1.0 Behaviour changed in blender/blender@49fc4449e7 **Short description of error** draw shader error ![image.png](https://archive.blender.org/developer/F14054952/image.png) It's normal:![image.png](https://archive.blender.org/developer/F14054958/image.png) **Exact steps for others to reproduce the error** Run the following code block and use the move gizmo. Drag or directly draw errors ``` import bpy import gpu from gpu_extras.batch import batch_for_shader coords = [(1, 1, 1), (-2, 0, 0), (-2, -1, 3), (0, 1, 1)] shader = gpu.shader.from_builtin('3D_POLYLINE_UNIFORM_COLOR') batch = batch_for_shader(shader, 'LINES', {"pos": coords}) def draw(): shader.uniform_float("color", (1, 1, 0, 1)) batch.draw(shader) bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW') ```

EMM commented

2022-12-13 05:03:56 +01:00

Added subscriber: @Guai_Wo_Ge_EMM

blender-admin commented

2022-12-13 05:03:56 +01:00

blender/blender#87118 was marked as duplicate of this issue

Pratik Borhade was assigned by EMM

2022-12-14 11:27:29 +01:00

Pratik Borhade commented

2022-12-14 11:55:32 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Pratik Borhade removed their assignment 2022-12-14 11:55:32 +01:00

Pratik Borhade commented

2022-12-14 11:55:32 +01:00

Added subscriber: @PratikPB2123

Pratik Borhade changed title from ~~3D shader 3D_POLYLINE_UNIFORM_COLOR draw error~~ to Regression: 3D shader 3D_POLYLINE_UNIFORM_COLOR draw error

2022-12-14 11:55:41 +01:00

Philipp Oeser commented

2023-01-02 10:54:46 +01:00

Added subscribers: @ideasman42, @lichtwerk

Philipp Oeser commented

2023-01-02 10:54:46 +01:00

Behaviour changed in blender/blender@49fc4449e7

CC @ideasman42

Said commit removed the drawing with GPU_SHADER_3D_UNIFORM_COLOR on the select pass (and instead always draws with GPU_SHADER_3D_POLYLINE_UNIFORM_COLOR now.
P3415 reverts that part (and it seems to work), but havent checked in depth...

Behaviour changed in blender/blender@49fc4449e7 CC @ideasman42 Said commit removed the drawing with `GPU_SHADER_3D_UNIFORM_COLOR` on the select pass (and instead always draws with `GPU_SHADER_3D_POLYLINE_UNIFORM_COLOR` now. [P3415](https://archive.blender.org/developer/P3415.txt) reverts that part (and it seems to work), but havent checked in depth...

Campbell Barton commented

2023-01-05 08:01:57 +01:00

Changed status from 'Confirmed' to: 'Archived'

Campbell Barton closed this issue

2023-01-05 08:01:57 +01:00

Campbell Barton commented

2023-01-05 08:01:57 +01:00

I don't think this is a bug: lineWidth and viewportSize uniforms need to be set.

This example works as expected:

import bpy
import gpu
from gpu_extras.batch import batch_for_shader

coords = [(1, 1, 1), (-2, 0, 0), (-2, -1, 3), (0, 1, 1)]
shader = gpu.shader.from_builtin('3D_POLYLINE_UNIFORM_COLOR')
batch = batch_for_shader(shader, 'LINES', {"pos": coords})


def draw():
    region = bpy.context.region
    shader.uniform_float("lineWidth", 8)
    shader.uniform_float("viewportSize", (region.width, region.height))
    shader.uniform_float("color", (1, 1, 0, 1))
    batch.draw(shader)


bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW')

I don't think this is a bug: `lineWidth` and `viewportSize` uniforms need to be set. This example works as expected: ``` import bpy import gpu from gpu_extras.batch import batch_for_shader coords = [(1, 1, 1), (-2, 0, 0), (-2, -1, 3), (0, 1, 1)] shader = gpu.shader.from_builtin('3D_POLYLINE_UNIFORM_COLOR') batch = batch_for_shader(shader, 'LINES', {"pos": coords}) def draw(): region = bpy.context.region shader.uniform_float("lineWidth", 8) shader.uniform_float("viewportSize", (region.width, region.height)) shader.uniform_float("color", (1, 1, 0, 1)) batch.draw(shader) bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW') ```

Philipp Oeser commented

2023-01-05 09:03:49 +01:00

@ideasman42 : OK, should this be mentioned in the documentation though ?

Campbell Barton commented

2023-01-06 07:22:38 +01:00

Added subscriber: @fclem

Campbell Barton commented

2023-01-06 07:22:38 +01:00

@lichtwerk this seems more like a general issue with documentation.
As I understand it the docs should state prominently stated that all uniforms need to be set, failure to do so may use a value from the last user of the uniform (which could be Blender or another script).

@fclem is this the case? or are there exceptions to this rule?

@lichtwerk this seems more like a general issue with documentation. As I understand it the docs should state prominently stated that all uniforms need to be set, failure to do so may use a value from the last user of the uniform (which could be Blender or another script). @fclem is this the case? or are there exceptions to this rule?

Clément Foucault commented

2023-01-06 10:25:38 +01:00

@ideasman42 yes this is correct. There is no exceptions as far as I can remember. But you can use that to you advantage when drawing multiple things with the same shader, changing only the uniforms that need to be changed.

Philipp Oeser commented

2023-01-06 10:45:12 +01:00

Changed status from 'Archived' to: 'Confirmed'

Philipp Oeser reopened this issue

2023-01-06 10:45:12 +01:00

Philipp Oeser commented

2023-01-06 10:45:12 +01:00

To not forget about this, will repoen as a TODO for documentation.

Philipp Oeser changed title from ~~Regression: 3D shader 3D_POLYLINE_UNIFORM_COLOR draw error~~ to Regression: 3D shader 3D_POLYLINE_UNIFORM_COLOR draw error (the need to set all shader uniforms need to be documented)

2023-01-06 10:46:16 +01:00

Michael Parkin-White commented

2023-01-06 11:49:54 +01:00

Added subscriber: @Michael-Parkin-White-Apple

Michael Parkin-White commented

2023-01-06 11:49:54 +01:00

As an additional note, since shaders have also been moved to GPUShaderCreateInfo, default uniform values are no longer valid in any case. Some shaders previously assigned default values directly in the uniform declaration. This feature removal was a requirement as this was not possible in Metal, when uniform values are always pulled directly from a GPU buffer or whole data block in the command stream.

Hence, if there are any other cases in Python add-ons which relied on default values being set, these may also no longer work as expected, especially if the default value is non-zero.

As an additional note, since shaders have also been moved to GPUShaderCreateInfo, default uniform values are no longer valid in any case. Some shaders previously assigned default values directly in the uniform declaration. This feature removal was a requirement as this was not possible in Metal, when uniform values are always pulled directly from a GPU buffer or whole data block in the command stream. Hence, if there are any other cases in Python add-ons which relied on default values being set, these may also no longer work as expected, especially if the default value is non-zero.

Philipp Oeser commented

2023-01-11 10:45:40 +01:00

Added subscribers: @MikhailRachinskiy, @Solstice245, @mano-wii, @Harley

John commented

2023-01-11 10:51:35 +01:00

@lichtwerk Thanks for directing me here. Campbell's short demonstration that they posted above was enough to figure out what I was doing wrong. Stick it in the docs somewhere maybe where people should expect to find that kinda thing ;p

Aaron Carlisle removed the

labels 2023-02-08 03:56:16 +01:00

Philipp Oeser referenced this issue from blender/blender

2023-04-03 13:04:06 +02:00

Different gpu line drawing in 3.5.0 #106459

Eugene Du commented

2023-04-03 13:22:57 +02:00

I don't think this is a bug: lineWidth and viewportSize uniforms need to be set.

This example works as expected:

import bpy
import gpu
from gpu_extras.batch import batch_for_shader

coords = [(1, 1, 1), (-2, 0, 0), (-2, -1, 3), (0, 1, 1)]
shader = gpu.shader.from_builtin('3D_POLYLINE_UNIFORM_COLOR')
batch = batch_for_shader(shader, 'LINES', {"pos": coords})


def draw():
    region = bpy.context.region
    shader.uniform_float("lineWidth", 8)
    shader.uniform_float("viewportSize", (region.width, region.height))
    shader.uniform_float("color", (1, 1, 0, 1))
    batch.draw(shader)


bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW')

Let me join your conversation.
So now to get anti-aliasing to work we need to complicate draw shader with additional calculations?
Since gpu.state.blend_set("ALPHA") works only with POLYLINE_UNIFORM_COLOR or POLYLINE_SMOOTH_COLOR as I know.
Is it heavier than old method?

Also, where we can get this 3D_POLYLINE_UNIFORM_COLOR? in the docs there is nothing https://docs.blender.org/api/current/gpu.shader.html

> I don't think this is a bug: `lineWidth` and `viewportSize` uniforms need to be set. > > This example works as expected: > > ``` > import bpy > import gpu > from gpu_extras.batch import batch_for_shader > > coords = [(1, 1, 1), (-2, 0, 0), (-2, -1, 3), (0, 1, 1)] > shader = gpu.shader.from_builtin('3D_POLYLINE_UNIFORM_COLOR') > batch = batch_for_shader(shader, 'LINES', {"pos": coords}) > > > def draw(): > region = bpy.context.region > shader.uniform_float("lineWidth", 8) > shader.uniform_float("viewportSize", (region.width, region.height)) > shader.uniform_float("color", (1, 1, 0, 1)) > batch.draw(shader) > > > bpy.types.SpaceView3D.draw_handler_add(draw, (), 'WINDOW', 'POST_VIEW') > ``` Let me join your conversation. So now to get anti-aliasing to work we need to complicate draw shader with additional calculations? Since `gpu.state.blend_set("ALPHA")` works only with `POLYLINE_UNIFORM_COLOR` or `POLYLINE_SMOOTH_COLOR` as I know. Is it heavier than old method? Also, where we can get this `3D_POLYLINE_UNIFORM_COLOR`? in the docs there is nothing https://docs.blender.org/api/current/gpu.shader.html

Andrej commented

2023-04-03 17:24:39 +02:00

So now to get anti-aliasing to work we need to complicate draw shader with additional calculations?

Yes, now you need to provide lineWidth and viewportSize uniforms and if you're using custom shader you also need to implement something similar to polylines yourself.

I'm not sure if it's heavier after all but now it does create 2 vertex for each line vertex to define line thickness and add some blending for anti-aliasing.

Code for builtins polyline shaders is here - https://projects.blender.org/blender/blender/src/branch/main/source/blender/gpu/shaders

Also, where we can get this 3D_POLYLINE_UNIFORM_COLOR? in the docs there is nothing

The same way as there is nothing about 3D_UNIFORM_COLOR.

>So now to get anti-aliasing to work we need to complicate draw shader with additional calculations? Yes, now you need to provide `lineWidth` and `viewportSize` uniforms and if you're using custom shader you also need to implement something similar to polylines yourself. I'm not sure if it's heavier after all but now it does create 2 vertex for each line vertex to define line thickness and add some blending for anti-aliasing. Code for builtins polyline shaders is here - https://projects.blender.org/blender/blender/src/branch/main/source/blender/gpu/shaders >Also, where we can get this 3D_POLYLINE_UNIFORM_COLOR? in the docs there is nothing The same way as there is nothing about `3D_UNIFORM_COLOR`.

👍 1

Germano Cavalcante commented

2023-04-05 19:13:47 +02:00

I don't think this should be considered a documentation error.
All builtins shader uniforms are indicated for example in: https://docs.blender.org/api/current/gpu.shader.html#module-gpu.shader

As with any parameter, a coder should already know that not setting a required value can result in undefined behavior.

It is not clear from this report how the documentation should be improved.

I don't think this should be considered a documentation error. All builtins shader uniforms are indicated for example in: https://docs.blender.org/api/current/gpu.shader.html#module-gpu.shader As with any parameter, a coder should already know that not setting a required value can result in undefined behavior. It is not clear from this report how the documentation should be improved.

Campbell Barton commented

2023-04-14 07:08:26 +02:00

A statement at the top of https://docs.blender.org/api/current/gpu.shader.html noting that uniforms are expected to be initialized by the scripts that use them would help.

Aaron Carlisle added the

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Aaron Carlisle added

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