给纯色单调的图片增加一层明暗纹理的shader

Shader code

shader_type canvas_item;

// Base layer
uniform bool use_base_texture = true;
uniform sampler2D base_texture : source_color;
uniform vec4 base_color : source_color = vec4(0.22, 0.24, 0.28, 1.0);

// Pattern layer
uniform bool use_pattern_texture = true;
uniform sampler2D pattern_texture : repeat_enable;
uniform float pattern_scale = 12.0;
uniform float pattern_strength : hint_range(0.0, 1.0, 0.001) = 0.18;
uniform float pattern_bias : hint_range(0.0, 1.0, 0.001) = 0.5;
uniform float pattern_rotation : hint_range(-180.0, 180.0, 0.1) = 0.0; // degrees
uniform vec2 pattern_scroll = vec2(0.0, 0.0);

// Blending controls
uniform bool use_dual_tone_pattern = true;
uniform float darken_strength : hint_range(0.0, 2.0, 0.001) = 0.9;
uniform float lighten_strength : hint_range(0.0, 2.0, 0.001) = 0.6;

// Extra controls
uniform float edge_fade_strength : hint_range(0.0, 1.0, 0.001) = 0.25;
uniform float brightness_response : hint_range(0.0, 2.0, 0.001) = 0.6;
uniform float alpha_strength : hint_range(0.0, 1.0, 0.001) = 0.0;

float luminance(vec3 c) {
	return dot(c, vec3(0.2126, 0.7152, 0.0722));
}

vec2 rotate_uv(vec2 uv, float deg) {
	float rad = radians(deg);
	float s = sin(rad);
	float c = cos(rad);
	mat2 m = mat2(vec2(c, -s), vec2(s, c));
	return m * uv;
}

void fragment() {
	// 1) Build base color from base texture (optional) + base_color tint
	vec4 sampled_base = vec4(1.0);
	if (use_base_texture) {
		sampled_base = texture(base_texture, UV);
	}
	vec4 base = sampled_base * base_color;

	// 2) Pattern sampling (optional). Neutral value around pattern_bias.
	float pattern_value = pattern_bias;
	if (use_pattern_texture) {
		vec2 p = UV - vec2(0.5);
		p = rotate_uv(p, pattern_rotation);
		vec2 pattern_uv = p * max(pattern_scale, 0.0001) + vec2(0.5) + pattern_scroll;
		pattern_value = texture(pattern_texture, pattern_uv).r;
	}

	// 3) Convert pattern to signed perturbation around bias
	float denom = max(pattern_bias, 1.0 - pattern_bias);
	float signed_delta = (pattern_value - pattern_bias) / max(denom, 0.0001);
	float dark_part = max(0.0, -signed_delta);
	float light_part = max(0.0, signed_delta);

	// 4) Edge fade to avoid clashing with frame borders
	vec2 d = abs(UV - vec2(0.5)) * 2.0;
	float edge_metric = clamp(max(d.x, d.y), 0.0, 1.0);
	float edge_fade = mix(1.0, 1.0 - edge_metric, edge_fade_strength);

	// 5) Brightness response: bright zones usually need weaker grain
	float luma = luminance(base.rgb);
	float brightness_factor = mix(1.0, 1.0 - luma, brightness_response);

	float influence = pattern_strength * edge_fade * brightness_factor;
	float darken = dark_part * darken_strength * influence;
	float lighten = light_part * lighten_strength * influence;

	vec3 shaded = base.rgb;
	if (use_dual_tone_pattern) {
		shaded = shaded * (1.0 - darken) + (1.0 - shaded) * lighten;
	} else {
		shaded = shaded * (1.0 - darken);
	}

	// Keep alpha readable; optionally let pattern affect alpha slightly
	float alpha_mod = mix(1.0, 1.0 - darken + lighten * 0.5, alpha_strength);
	float out_alpha = clamp(base.a * alpha_mod, 0.0, 1.0);

	COLOR = vec4(clamp(shaded, 0.0, 1.0), out_alpha);
}

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