Viewport doesn't show or render vertex painted alpha. #58711

New Issue

James Ovnik · 2018-12-04T13:34:40+01:00

James Ovnik commented

2018-12-04 13:34:40 +01:00

System Information
Operating system: Windows 10 64bit
Graphics card: GeForce GTX 1080 Ti

Blender Version

Broken: 2.80, 1b6a394d86, blender2.8, 2018-12-03

Worked: 2.79 master, 1b974563b1, blender2.8, 2018-11-01

Short description of error

When applying alpha values to a mesh's vertices in Vertex Paint mode the viewport doesn't render the alpha. I've tried all the display modes (Solid/Lookdev and rendered (Eevee & cycles) ) but none render the painted alpha values.

I've attached a simple cube scene where the mesh has been painted with green vertex color, with the uppermost verts having alpha values. I've confirmed the alpha values are there and correct by opening the scene in 2.79 master where the Cube renders correctly, I've also imported to Maya where the again the cube renders correctly.

Vertex_Alpha_Cube.blend

system-info.txt

Exact steps for others to reproduce the error

Open attached .blend, select mesh and go to Vertex Paint mode. Cycle through the different viewport display modes and you'll see no alpha rendered.

**System Information** Operating system: Windows 10 64bit Graphics card: GeForce GTX 1080 Ti **Blender Version** Broken: 2.80, 1b6a394d862, blender2.8, 2018-12-03 Worked: 2.79 master, 1b974563b17, blender2.8, 2018-11-01 **Short description of error** When applying alpha values to a mesh's vertices in Vertex Paint mode the viewport doesn't render the alpha. I've tried all the display modes (Solid/Lookdev and rendered (Eevee & cycles) ) but none render the painted alpha values. I've attached a simple cube scene where the mesh has been painted with green vertex color, with the uppermost verts having alpha values. I've confirmed the alpha values are there and correct by opening the scene in 2.79 master where the Cube renders correctly, I've also imported to Maya where the again the cube renders correctly. ![Vertex_Alpha_in_2_8.PNG](https://archive.blender.org/developer/F5810684/Vertex_Alpha_in_2_8.PNG) ![Vertex_Alpha_in_2_79.PNG](https://archive.blender.org/developer/F5810652/Vertex_Alpha_in_2_79.PNG) ![Vertex_Alpha_in_Maya.PNG](https://archive.blender.org/developer/F5810657/Vertex_Alpha_in_Maya.PNG) [Vertex_Alpha_Cube.blend](https://archive.blender.org/developer/F5810665/Vertex_Alpha_Cube.blend) [system-info.txt](https://archive.blender.org/developer/F5810693/system-info.txt) **Exact steps for others to reproduce the error** Open attached .blend, select mesh and go to Vertex Paint mode. Cycle through the different viewport display modes and you'll see no alpha rendered.

James Ovnik commented

2018-12-04 13:34:40 +01:00

Added subscriber: @JamesOvnik

Sebastian Parborg commented

2018-12-06 17:06:37 +01:00

Added subscriber: @ZedDB

Clément Foucault was assigned by Sebastian Parborg

2018-12-06 17:06:37 +01:00

Sebastian Parborg commented

2018-12-06 17:06:37 +01:00

The appended file does not work in 2.79 (it seems to be a 2.8 file).
However if you:

Open the default cube scene in 2.79
Go into vertex paint
Choose the subtract brush and choose pick black as color.
Paint some verts with the subtract brush
Those verts should now have a visible transparent alpha value

I'm guessing that the draw methods in 2.8 does not support showing these alpha values.

@JamesOvnik did this ever work in blender 2.8? I've tried a to roll back to a 2.8 build from 11-01 and it still had this issue...

The appended file does not work in 2.79 (it seems to be a 2.8 file). However if you: 1. Open the default cube scene in 2.79 2. Go into vertex paint 3. Choose the subtract brush and choose pick black as color. 4. Paint some verts with the subtract brush 5. Those verts should now have a visible transparent alpha value I'm guessing that the draw methods in 2.8 does not support showing these alpha values. @JamesOvnik did this ever work in blender 2.8? I've tried a to roll back to a 2.8 build from 11-01 and it still had this issue...

James Ovnik commented

2018-12-06 17:20:42 +01:00

@ZedDB

Hi Sebastian, to the best of my knowledge this has been broken in all versions of 2.8 that I've tried.
Also worth noting is that the painting of vertex alpha is only possible in 2.79 master. It has never worked in 2.79 official.

@ZedDB Hi Sebastian, to the best of my knowledge this has been broken in all versions of 2.8 that I've tried. Also worth noting is that the painting of vertex alpha is only possible in 2.79 master. It has never worked in 2.79 official.

michael knubben commented

2019-02-25 10:20:12 +01:00

Added subscriber: @michaelknubben

Clément Foucault commented

2019-03-20 19:32:10 +01:00

Added subscriber: @brecht

Clément Foucault commented

2019-03-20 19:32:10 +01:00

Well the issue is that we don't draw the vertex paint as part of the mesh but as an overlay.

Workbench does not support Alpha blending (it just supports OIT) so supporting VCol alpha would be very weird visually.

If Cycles would support this I would happily support it the same way in Eevee. But we must agree first on implementation with @brecht. As far as I know, Color sockets cannot use Alpha values because of OSL restrictions. Would the Fac output the alpha of the vertex color layer?

Well the issue is that we don't draw the vertex paint as part of the mesh but as an overlay. Workbench does not support Alpha blending (it just supports OIT) so supporting VCol alpha would be very weird visually. If Cycles would support this I would happily support it the same way in Eevee. But we must agree first on implementation with @brecht. As far as I know, Color sockets cannot use Alpha values because of OSL restrictions. Would the Fac output the alpha of the vertex color layer?

Brecht Van Lommel commented

2019-03-20 19:36:05 +01:00

Using the Fac output for alpha seems a bit weak. Perhaps it would be better to add a new Vertex Color node similar to how we have UV Map, with color and alpha outputs.

Vasil commented

2019-07-10 10:05:54 +02:00

Added subscriber: @FeralMan

Vasil commented

2019-07-10 10:05:55 +02:00

Hi guys, I'm working now on a project that uses "Vertex Paint" instead "Textures". I paint a lot of buildings needed for my project in Blender 2.8. But Now I need Alpha-Transparency support for the glow effect. What is the progress on support alpha-transparency? I'm interested in this feature to be developt.
I found a cheesy way to make it with the shader, you can read here https://blenderartists.org/t/vertex-paint-with-alpha-transperency/1164322
But it's not a cure.
Maybe some of the developer an interested and we can create a branch for "Vertex paint" feature. It's also lacking in layers system for painting. So it has a place for improvements.

Hi guys, I'm working now on a project that uses "Vertex Paint" instead "Textures". I paint a lot of buildings needed for my project in Blender 2.8. But Now I need Alpha-Transparency support for the glow effect. What is the progress on support alpha-transparency? I'm interested in this feature to be developt. I found a cheesy way to make it with the shader, you can read here https://blenderartists.org/t/vertex-paint-with-alpha-transperency/1164322 But it's not a cure. Maybe some of the developer an interested and we can create a branch for "Vertex paint" feature. It's also lacking in layers system for painting. So it has a place for improvements.

Maestro Pivetta commented

2019-07-15 15:26:46 +02:00

Added subscriber: @M.Pivetta

Maestro Pivetta commented

2019-07-15 15:26:47 +02:00

@fclem Is actually the not having support for alpha blending but only OIT or the overlay system the reason for being unable to hide mesh parts in Weight Painting and Vertex Coloring? (parts are not editable and invisible to the tools but still rendered so they are just in the way - it's clumsy somehow)

Clément Foucault was unassigned by Dalai Felinto

2019-12-23 16:35:44 +01:00

Dalai Felinto commented

2019-12-23 16:35:44 +01:00

Added subscriber: @fclem

Sebastian Parborg commented

2020-01-17 16:32:11 +01:00

Closed as duplicate of #71947

Sebastian Parborg closed this issue

2020-01-17 16:32:11 +01:00

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Viewport doesn't show or render vertex painted alpha. #58711