shader_type spatial;
render_mode blend_mix, cull_back, diffuse_burley, specular_schlick_ggx;

// --- Parameters -------------------------------------------------------
// Solid tint colors, one per vertex-color channel (R, G, B).
uniform vec3 color_red   : source_color = vec3(1.0, 0.0, 0.0);
uniform vec3 color_green : source_color = vec3(0.0, 1.0, 0.0);
uniform vec3 color_blue  : source_color = vec3(0.0, 0.0, 1.0);

// The brush texture. Its R/G/B channels each hold a different brush-stroke
// variation, used purely as an alpha/shape mask (not as color).
uniform sampler2D pattern_texture : hint_default_black, repeat_enable, filter_linear_mipmap;

// How many times the brush pattern repeats over the mesh UVs.
uniform vec2 pattern_tiling = vec2(1.0, 1.0);

// --- Hard region selection ---------------------------------------------
// Vertex color picks the region on/off (assumes verts are painted with
// clean, mostly-pure R/G/B — not blended mixes). Threshold decides how
// strong a channel needs to be to count as "painted", smoothness gives
// a tiny anti-aliased edge instead of a jagged one.
uniform float region_threshold : hint_range(0.0, 1.0) = 0.5;
uniform float region_smoothness : hint_range(0.0, 0.5) = 0.05;

void fragment() {
	vec4 tex = texture(pattern_texture, UV * pattern_tiling);

	// Hard (but lightly smoothed) on/off mask per channel from vertex color.
	float mask_r = smoothstep(region_threshold - region_smoothness, region_threshold + region_smoothness, COLOR.r);
	float mask_g = smoothstep(region_threshold - region_smoothness, region_threshold + region_smoothness, COLOR.g);
	float mask_b = smoothstep(region_threshold - region_smoothness, region_threshold + region_smoothness, COLOR.b);

	// Inside each region, the matching texture channel is only the brush
	// stroke's alpha/shape — the actual color comes from the tint uniform.
	vec3 result =
		  mask_r * color_red   * tex.r
		+ mask_g * color_green * tex.g
		+ mask_b * color_blue  * tex.b;

	ALBEDO = result;
}