UV light (2D and 3D)

This is an example of a “UV light” effect, useful for secret objects and messages. It works both with 3D geometry (where the shape is defined by a mesh) and with flat objects (where the shape/pattern is defined by texture’s alpha).

Requirements:

• put all secret objects in a separate layer (property layers, in this example it’s “Layer 2”)
• remove that layer from normal light sources (property light_cull_mask)
• make sure that UV light sources affect that layer (property light_cull_mask)

Shader code

// 2D objects, e.g. text on a wall, where the shape is defined by a texture
shader_type spatial;

uniform sampler2D tex;
uniform vec4 color: source_color = vec4(0, 1, 1, 1);
uniform float energy: hint_range(0, 16) = 1;

void fragment() {
	EMISSION = color.rgb * energy;
	ALPHA = 0.0;
}

void light() {
	vec4 pixel = textureLod(tex, UV, 1.0);
	DIFFUSE_LIGHT = vec3(0.0);
	SPECULAR_LIGHT = vec3(0.0);
	ALPHA = ATTENUATION * pixel.a;
	if (ATTENUATION == 1.0) {
		ALPHA = 0.0;
	}
}

// 3D objects, e.g. a ghost, where the shape is defined by geometry
shader_type spatial;

uniform vec4 color: source_color = vec4(0, 1, 1, 1);
uniform float energy: hint_range(0, 16) = 1;

void fragment() {
	EMISSION = color.rgb * energy;
	ALPHA = 0.0;
}

void light() {
	DIFFUSE_LIGHT = vec3(0.0);
	SPECULAR_LIGHT = vec3(0.0);
	ALPHA = ATTENUATION;
	if (ATTENUATION == 1.0) {
		ALPHA = 0.0;
	}
}

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