Is there a way to use a transparent texture in Beer/Malt?

[MeganDrawsaLot]

I've been trying to see if I can use transparent textures while using the Malt render engine. I've tried using the Basic Texture Shader, but there is no transparency when I use a .png. Is there a way I could change the shaders code to achieve this, and make a texture visible without having to add a light to the scene?
I feel like this could be very helpful for adding painted layers, like for highlights in hair, or tattoo designs. Right now I'm trying to have my logo next to the character I'm working on in blender.

For the example I pushed the logo to sit in front of the character more, to try and be clearer about what I mean.

[pragma37]

I've tried using the Basic Texture Shader, but there is no transparency when I use a .png.

If you look at the code, the line 13 is reading only the rgb channels:

vec3 diffuse_color = texture(diffuse_texture, UV[uv_index]).rgb;

If you just want a flat texture without lighting, you could use a shader that simply outputs the full texture rgba values as the pixel color output:

#include "Pipelines/NPR_Pipeline.glsl"

uniform sampler2D diffuse_texture;
uniform int uv_index = 0;

void COMMON_PIXEL_SHADER(Surface S, inout PixelOutput PO)
{
    PO.color = texture(diffuse_texture, S.uv[uv_index]);
}

If you want to adapt the basic_texture.mesh.glsl you could just use the texture alpha as pixel color output alpha:

#include "Pipelines/NPR_Pipeline.glsl"

uniform vec3 ambient_color = vec3(0.1,0.1,0.1);
uniform sampler2D diffuse_texture;
uniform int uv_index = 0;
uniform vec3 specular_color = vec3(1.0,1.0,1.0);
uniform float roughness = 0.5;

void COMMON_PIXEL_SHADER(Surface S, inout PixelOutput PO)
{
    vec4 diffuse_color = texture(diffuse_texture, S.uv[uv_index]);
    vec3 diffuse = diffuse_color.rgb * get_diffuse();
    vec3 specular = specular_color * get_specular(roughness);
    vec3 color = ambient_color + diffuse + specular;

    PO.color.rgb = color;
    PO.color.a = diffuse_color.a;
}

By default, only pixels with alpha 0 will be transparent and the rest will be fully opaque. If you want alpha blending enable the Transparency options in the material UI.

[MeganDrawsaLot]

I think I am getting the general idea of it, my brain just needs to learn how to take in and sort all the new information.
Thank you once again for the help! I think I'll be able to figure it out, but will definitely ask more questions if I get majorly stuck. :)

[MeganDrawsaLot]

I got it!!! Yay!

Is there a glsl code I can use to get the grease-pencil to show up behind the transparent texture as well.
...I've uh, got another question as well but I don't want to take up to much of your time. ^^;

Here's the code so far.

//Copyright (c) 2020 BlenderNPR and contributors. MIT license.

#include "Pipelines/NPR_Pipeline.glsl"

uniform vec3 ambient_color = vec3(0.1,0.1,0.1);
uniform vec3 diffuse_color = vec3(1.0,0.1,0.1);

uniform sampler2D diffuse_texture;
uniform int uv_index = 0;

uniform vec3 specular_color = vec3(1.0,1.0,1.0);
uniform float roughness = 0.5;

uniform bool line_world_space = false;

uniform vec4 line_color = vec4(0.0,0.0,0.0,1.0);

uniform float line_id_boundary_width = 1.;

uniform float line_depth_threshold_min = 0.5;
uniform float line_depth_threshold_max = 2.0;
uniform float line_depth_width_min = 0.5;
uniform float line_depth_width_max = 2.0;

uniform float line_angle_threshold_min = 0.5;
uniform float line_angle_threshold_max = 1.5;
uniform float line_angle_width_min = 0.5;
uniform float line_angle_width_max = 2.0;


void COMMON_PIXEL_SHADER(Surface S, inout PixelOutput PO)
{

    vec4 diffuse_color = texture(diffuse_texture, S.uv[uv_index]);
    vec3 diffuse = diffuse_color.rgb * get_diffuse();
    vec3 specular = specular_color * get_specular(roughness);
    vec3 color = ambient_color + diffuse + specular;

    
    
    float line = get_line_advanced(
        line_id_boundary_width,
        line_depth_threshold_min, line_depth_threshold_max, line_depth_width_min, line_depth_width_max,
        line_angle_threshold_min, line_angle_threshold_max, line_angle_width_min, line_angle_width_max);
    
    if(line_world_space)
    {
        line /= pixel_world_size_at(pixel_depth());
        // Here we divide by 100 just to make line size more consistent between modes,
        // but this is a completely optional hand-picked number
        line /= 100;
    }

    PO.color = texture(diffuse_texture, S.uv[uv_index]);
    PO.line_color = line_color;
    PO.line_width = line * S.color[0].r;
}

[MeganDrawsaLot]

Here's a picture of what I was talking about with the grease pencil.

[pragma37]

Yay! Congrats!

There's no way to fix that grease pencil issue afaik, sorry. I think even EEVEE and Cycles don't support that at the moment.
Basically grease pencil does its own rendering, so it's a take it or leave it situation.

I think you can convert grease pencil objects to mesh objects, though.

[MeganDrawsaLot]

Converting it to mesh was my next thought! :)

Okay here's another idea; is there any way to make a transparent cube, that has line art, in Malt? This is more for curiosities sake. I Made a cube and put my logo on it and found out that shader for the lines work around the alpha channel/will outline the logo itself. I was wondering if the cube could be outlined while still retaining the transparent mesh. I don't know what I'd use this method for (yet) but my brain is kind of itching to know if it can be done.

Thanks again for your prompt answers!