Screen Space Mesh Projection

This shader projects a 3d mesh into screen space like a UI element.

Shader code

shader_type spatial;
render_mode unshaded, skip_vertex_transform, depth_draw_always, depth_prepass_alpha;
uniform vec2 SCREEN_POSITION = vec2(0.0);
uniform float scale: hint_range(0.0, 1.0, 0.01) = 0.5;

float lerp(float a, float b, float t) {
	return a + (b-a) * t;
}

float inverse_lerp(float a, float b, float t) {
	return (t - a) / (b - a);
}

float remap(float value, float istart, float istop, float ostart, float ostop) {
	return lerp(ostart, ostop, inverse_lerp(istart, istop, value));
}

void vertex() {
	vec4 verts = vec4(VERTEX, 1.0);
	
	verts = PROJECTION_MATRIX * MODEL_MATRIX * verts;
	
	POSITION.xyz = verts.xyz;
	POSITION.xy *= scale;
	POSITION.xy += SCREEN_POSITION;
	
	POSITION.z = remap(POSITION.z, -1.0, 1.0, 0.8, 1.0);
	
	NORMAL = normalize((MODEL_MATRIX * vec4(NORMAL, 0.0)).xyz);
	BINORMAL = normalize((MODEL_MATRIX * vec4(BINORMAL, 0.0)).xyz);
	TANGENT = normalize((MODEL_MATRIX * vec4(TANGENT, 0.0)).xyz);
}

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