(Quick example image I just made)

I'm making a simple android game with kha and I need to apply an opacity mask, so I just have 1 opacity texture and I reuse it across a lot of diffuse textures instead of making a lot of .png files with the opacity included them. I want to know if this is possible, and how to do it. Thanks.

Yes but do you use g2 or g4?

@Robert g2

You will need to learn a little bit of g4 then. Here's a sample for how to set a shader in g2: https://github.com/Kha-Samples/Shader-G2
After you set the pipeline you have to set a second texture - in the shader you can then use color from the first texture and alpha from the second texture.

@Robert Ok, thank you

I beg your pardon, may I request your help again? (I know, it's been a while since I posted this, I didn't know how to do it and I've been busy lately but today I gave it a shot and finally I've figured some basic stuff out.)

I'm stuck on the second texture step.

Here's my ImageObject.hx (The whole pipeline set-up is in Project.hx but I don't think it's necessary to show it)

package;

import kha.Assets;
import kha.graphics2.Graphics;
import kha.Color;
import kha.Image;

import Entity;



class ImageObject extends Entity{
	public var image:Image;
	//public var mask:Image; ?
	public function new(image:Image,x:Float, y:Float, width:Int, height: Int){
	this.image = image;
	super(x, y, width, height);
}

public function update(){

}

public function render(graphics:Graphics){

		//graphics.color = Color.Green;
		graphics.pipeline = Project.pipeline;
		//Dibujar imagen!!! Se divide X entre 2 para centrarlo con el raton, al igual que con Y
		graphics.drawScaledImage(image,x - width / 2, y,width * 1.1, height * 1.1);

		

}

}

And the fragment shader:

#version 450

uniform sampler2D tex;
uniform sampler2D mask;
in vec2 texCoord;
in vec4 color;


out vec4 FragColor;

void main() {
	vec4 texcolor = texture(tex, texCoord) * color;
	texcolor.rgb *= color.a;
	texcolor.rgb = texcolor.bgr; // swap color channels
	if(texture(mask, texCoord).a != 1.0f)
    {
        discard;
    }
   FragColor = texture(tex, texCoord);
}

Ok, I have Image, which is my diffuse texture, but now I'm stuck doing the mask. What do I have to do to make the shader recognize a 2nd texture and set is as "uniform sampler2D mask;"?
PD: The shader itself is working (Colors channels do get swapped)

pipeline.getTextureUnit and g4.setTexture are what you need - put the setTexture call right before your drawScaledImage call.

Can you make me a quick example please? I can't find any online documentation about how it works, no more than
"pipeline.getTextureUnit();, you have put a string between the parenthesis"

Here's a small and quick to work through tutorial-series for you: https://github.com/luboslenco/kha3d_examples (number 5 is the first one which uses a texture)