learnOpenGL 2.5 多光源

之前我们学习了多种光源，也介绍了他们的计算方法。

当画面中有多个光源时，为了方面管理和计算光照，我们将它们分别建立结构体和计算函数。

struct dirLight{
	vec3 direction;

	vec3 ambient;
	vec3 diffuse;
	vec3 specular;

	float constant;
	float linear;
	float quadratic;
};

struct pointLight{
	vec3 position;
	vec3 ambient;
	vec3 diffuse;
	vec3 specular;

	float constant;
	float linear;
	float quadratic;
};
struct spotLight{
	vec3 ambient;
	vec3 diffuse;
	vec3 specular;

	vec3 position;
	vec3 direction;

	float constant;
	float linear;
	float quadratic;

	float cutoff;
	float outcutoff;
};

计算函数以聚光光源为例

vec3 calcspotlight(spotLight spotlight,vec3 normal,vec3 viewdir,vec3 fragpos)
{
	vec3 ambient=spotlight.ambient*texture(material.diffuse,texcoor).rgb;

	vec3 lightdir=normalize(spotlight.position-fragpos);
	float diff=max(dot(lightdir,normal),0);
	vec3 diffuse=diff*spotlight.diffuse*texture(material.diffuse,texcoor).rgb;

	vec3 reflectdir=normalize(reflect(-lightdir,normal));
	float spec=pow(max(dot(reflectdir,viewdir),0),material.shininess);
	vec3 specular=spotlight.specular*spec*texture(material.specular,texcoor).rgb;

	float distance=length(spotlight.position-fragpos);
	float attenuation=1.0/(spotlight.constant+spotlight.linear*distance+spotlight.quadratic*distance*distance);
	ambient *= attenuation; 
    diffuse *= attenuation;
    specular *= attenuation;   

	float theta=dot(normalize(-spotlight.direction),lightdir);
	float epsilon=spotlight.cutoff-spotlight.outcutoff;
	float intensity=clamp((theta-spotlight.outcutoff)/epsilon,0.0,1.0);
	diffuse*=intensity;
	specular*=intensity;

	return (ambient+diffuse+specular);
}

这样一来我们在shader的主函数中就只要调用这些计算函数了，多光源的计算也会变得方便许多。

void main()
{
	vec3 norm=normalize(normal);
	vec3 viewdir=normalize(viewpos-fragpos);

	vec3 result=calcdirlight(dirlight,norm,viewdir);
	for(int i=0;i<4;i++)
		result+=calcpointlight(pointlight[i],norm,viewdir,fragpos);
	result+=calcspotlight(spotlight,norm,viewdir,fragpos);

	FragColor=vec4(result,1.0f);
}