static const GLchar *plug_vertex_lighting_ADSLightModel = "\n\
/* use ADSLightModel here the ADS colour is returned from the function.  */ \n\
void PLUG_add_light_contribution2 (inout vec3 vertexcolor, inout vec3 specularcolor, in vec4 myPosition, in vec3 myNormal, \n\
		in float mat_shininess, in float mat_ambient, in vec3 mat_diffuse, in vec3 mat_specular){ \n\
	//working in eye space: eye is at 0,0,0 looking generally in direction 0,0,-1 \n\
	//myPosition, myNormal - of surface vertex, in eyespace \n\
	//vertexcolor - diffuse+ambient -will be replaced or modulated by texture color \n\
	//specularcolor - specular+emissive or non-diffuse (emissive added outside this function) \n\
	//algo: uses Blinn-Phong specular reflection: half-vector pow(N*H,shininess) \n\
	// https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/lighting.html#Lightingequations \n\
	// fog and emissive are done elsewhere, this function does: \n\
	// SUM(on[i] x attenuation[i] x spot[i] x ILrgb[i] x (ambient[i] + diffuse[i] + specular[i])) \n\
	int i; \n\
	vec3 N = normalize (myNormal); \n\
		\n\
	vec3 E = -normalize(myPosition.xyz); \n \
		\n\
	// apply the lights to this material \n\
	// weird but ANGLE needs constant loop \n\
	vec3 sum_vertex = vec3(0.,0.,0.); \n\
	vec3 sum_specular = vec3(0.,0.,0.); \n\
	for (i=0; i<lightcount; i++) {\n\
		vec3 diffuse = vec3(0., 0., 0.); \n\
		vec3 ambient = vec3(0., 0., 0.); \n\
		vec3 specular = vec3(0., 0., 0.); \n\
		float on = 1.0; //we only send active/on lights to shader, so this is for radius \n\
		float spot = 1.0; \n\
		float attenuation = 1.0; //directional default \n\
		fw_LightSourceParameters light = fw_LightSource[i]; \n\
		int myLightType = lightType[i]; \n\
		// VP vector of light direction and distance \n\
		vec3 VP = light.location.xyz - myPosition.xyz; \n\
		vec3 L = -light.direction; //directional light \n\
		if(myLightType < 2){ \n\
			//point and spot \n\
			L = normalize(VP); \n\
			float D = length(VP);  // distance to vertex \n\
			// are we within range? \n\
			if (D > light.lightRadius) on = 0.0; \n\
			attenuation = 1.0/max(1.0,(light.Attenuations.x + (light.Attenuations.y * D) + (light.Attenuations.z *D*D))); \n\
		} \n\
		float NdotL = max(dot(N, L), 0.0); //Lambertian diffuse term \n\
		//specular reflection models, phong or blinn-phong \n\
		//#define PHONG 1 \n\
		#ifdef PHONG \n\
			//Phong \n\
			vec3 R = normalize(-reflect(L,N)); \n\
			float RdotE = max(dot(R,E),0.0); \n\
			float specbase = RdotE; \n\
			// assume shader gets shininess in 0 to 1 range, and scales it to 0 to 128 range here \n\
			float specpow = mat_shininess*128.0; \n\
		#else //PHONG \n\
			//Blinn-Phong \n\
			vec3 H = normalize(L + E); //halfvector x3d specs this is L+v/|L+v|\n\
			float NdotH = max(dot(N,H),0.0); \n\
			float specbase = NdotH; \n\
			float specpow = mat_shininess*128.0; \n\
		#endif //PHONG \n\
		float powerFactor = 0.0; // for light dropoff \n\
		if (specbase > 0.0) { \n\
			powerFactor = pow(specbase,specpow); \n\
			// tone down the power factor if mat_shininess borders 0 \n\
		} \n\
			\n\
		ambient += light.ambient * mat_diffuse * mat_ambient; \n\
		specular += light.intensity * mat_specular *powerFactor; \n\
		diffuse += light.intensity * mat_diffuse * NdotL; \n\
		if (myLightType==1) { \n\
			// SpotLight  \n\
			spot = 0.0; \n\
			float spotDot = dot (-L,light.direction); \n\
			// check against spotCosCutoff \n\
			if (spotDot > light.spotCutoff) { \n\
				if(spotDot > light.spotBeamWidth) { \n\
					spot = 1.0; \n\
				} else { \n\
					spot = (spotDot - light.spotCutoff)/(light.spotBeamWidth - light.spotCutoff); \n\
				} \n\
			} \n\
		} \n\
		sum_vertex   += on * attenuation * spot * light.color * (ambient + diffuse); \n\
		sum_specular += on * attenuation * spot * light.color * (specular); \n\
	} \n\
	vertexcolor = clamp(sum_vertex + vertexcolor, 0.0, 1.0); \n\
	specularcolor = clamp(sum_specular + specularcolor, 0.0, 1.0); \n\
} \n\
";