armorpaint/paint/shaders/layer_view.kong

#[set(everything)]
const constants: {
	pos: float4; // xywh
	tex: float4; // xywh
	col: float4;
	channel: int;
};

#[set(everything)]
const sampler_linear: sampler;

#[set(everything)]
const tex: tex2d;

struct vert_in {
	pos: float2;
}

struct vert_out {
	pos: float4;
	tex: float2;
	col: float4;
}

fun layer_view_vert(input: vert_in): vert_out {
	var output: vert_out;

	var cpos: float4 = constants.pos;
	var ctex: float4 = constants.tex;

	output.pos = float4(input.pos, 0.0, 1.0);
	output.pos.xy = output.pos.xy * cpos.zw + cpos.xy;
	output.pos.xy = output.pos.xy * 2.0 - 1.0;
	output.pos.y = -output.pos.y;
	output.tex = input.pos * ctex.zw + ctex.xy;
	output.col = constants.col;
	return output;
}

fun layer_view_frag(input: vert_out): float4 {
	if (constants.channel == 1) {
		return sample_lod(tex, sampler_linear, input.tex, 0.0).rrra * input.col;
	}
	if (constants.channel == 2) {
		return sample_lod(tex, sampler_linear, input.tex, 0.0).ggga * input.col;
	}
	if (constants.channel == 3) {
		return sample_lod(tex, sampler_linear, input.tex, 0.0).bbba * input.col;
	}
	if (constants.channel == 4) {
		return sample_lod(tex, sampler_linear, input.tex, 0.0).aaaa * input.col;
	}
	if (constants.channel == 5) {
		return sample_lod(tex, sampler_linear, input.tex, 0.0).rgba * input.col;
	}
	// else {
		var tex_sample: float4 = sample_lod(tex, sampler_linear, input.tex, 0.0);
		tex_sample.rgb = tex_sample.rgb * tex_sample.a;
		return tex_sample * input.col;
	// }
}

#[pipe]
struct pipe {
	vertex = layer_view_vert;
	fragment = layer_view_frag;
}