phong模型和blinnphong模型简述

简介

phong 和 blinnphong 都是比较常用的光照模型

参考链接

https://github.com/Richbabe/Phong-BlinnPhong_Unity 非常好讲的
https://blog.csdn.net/weixin_34321977/article/details/93246573 一般般
https://blog.csdn.net/qq_32974399/article/details/107096490 reflect算法的图解, 非常好
https://blog.csdn.net/yuebaidada/article/details/90749299 phong模型关于 \((R\dot V)^n\) 关于n的讲解非常好, 随着n增大, 离镜面反射的区域将迅速缩小

phong Image

blinn phong

code phong

#version 420 
out vec4 FragColor;
in vec3 pos;
in vec3 color;
uniform int colormode = 1;
uniform int drawmode = 1;


void main() {  
	if(colormode == 0){
		FragColor = vec4(color,1.0);
	} else if (colormode == 1) {
        if(drawmode == 0){
            FragColor = vec4(0.25,0.25,0.25,1.0);
        } else {
            vec3 n = normalize(cross(dFdx(pos),dFdy(pos)));
	        vec3 lposition = vec3(0.0f,0.0f, 20f);
            vec3 viewposition = vec3(0.0f,0.0f, 20f);
            float f_ambient = 0.4f;
            float f_spec = 0.7f;
            // ambient
            vec3 light = vec3(1f, 1f, 1f);
            vec3 ambient = light * f_ambient;

            // diffuse
            vec3 lightDir = normalize(lposition - pos);
            
            vec3 diff = ambient * max(0.0, dot(n, lightDir));

            // specular
            vec3 viewDir = normalize(viewposition - pos);
            vec3 reflectDir = reflect(-lightDir, n); 
            float spec =  pow(max(dot(viewDir, reflectDir), 0.0), 16.0f) * f_spec;
            vec3 specular = ambient * spec;
            vec3 result = ambient + diff + specular;

            FragColor = vec4(result, 1.0);
        }
	} else {
        FragColor = vec4(1.0, 0.0, 0.0, 1.0);
    }
}

code blinnphong

#version 420 
out vec4 FragColor;
in vec3 pos;
in vec3 color;
uniform int colormode = 1;
uniform int drawmode = 1;


void main() {  
	if(colormode == 0){
		FragColor = vec4(color,1.0);
	} else if (colormode == 1) {
        if(drawmode == 0){
            FragColor = vec4(0.25,0.25,0.25,1.0);
        } else {
            vec3 n = normalize(cross(dFdx(pos),dFdy(pos)));
	        vec3 lposition = vec3(0.0f,0f, 20f);
            vec3 viewposition = vec3(0.0f,0.0f, 20f);
            float f_ambient = 0.4f;
            float f_spec = 0.7f;
            // ambient
            vec3 light = vec3(1f, 1f, 1f);
            vec3 ambient = light * f_ambient;

            // diffuse
            vec3 lightDir = normalize(lposition - pos);
            
            vec3 diff = ambient * max(0.0, dot(n, lightDir));

            // specular
            vec3 viewDir = normalize(viewposition - pos);
            //vec3 reflectDir = reflect(-lightDir, n);
            vec3 half = normalize(lightDir+viewDir);
            //vec3 half = normalize(lightDir),motmalize(viewDir);
            float spec =  pow(max(dot(n, half), 0.0), 256.0f) ;
            vec3 specular = light * spec * f_spec;
            vec3 result = ambient + diff + specular;

            FragColor = vec4(result, 1.0);
        }
	} else {
        FragColor = vec4(1.0, 0.0, 0.0, 1.0);
    }
}

简述原理 phong

float spec = pow(max(dot(viewDir, reflectDir), 0.0), 16.0f) * f_spec;
简单来说就是R和V的向量夹角越小. 反射效果越

简述原理 blinnphong

float spec = pow(max(dot(n, half), 0.0), 256.0f) ;
简单来说就是,V和H向量之间的夹角. H就是L+Eye向量的单位向量. 简单而言是为了减少计算.