【发布时间】：2017-07-30 18:32:08
【问题描述】：
我正在为物理引擎制作一个相对简单的渲染（类似于this）。我只是在学习 OpenGL，并且一直在关注这个tutorial。我希望我的渲染器能够处理从以下类型中选择的少量灯光：定向光、点光、聚光灯和区域光。我也想要使用阴影贴图的简单阴影。因此，例如，一个场景可能包含两个聚光灯或一个定向光或一个点光和一个聚光灯等。目前我有一个更大的着色器可以一起处理所有灯光，但是现在我正在尝试使用阴影贴图，它看起来很轻更好（从模块化设计的角度来看）为每种灯光或至少每种灯光类型使用不同的着色器。我想知道从效率的角度来看，这是否是一个合理的想法。为了使这更具体，我当前的顶点如下所示：
#version 130
in vec3 position;
in vec3 normal;
in vec2 atexture;
out vec3 FragPos;
out vec3 Normal;
out vec2 TexCoord;
out vec4 FragPosLightSpace;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
uniform mat4 lightView;
uniform mat4 lightProjection;
void main()
{
gl_Position = projection * view * model * vec4(position.x, position.y, position.z, 1.0);
FragPos = vec3(model * vec4(position, 1.0));
Normal = normalize(normal);
TexCoord = atexture;
FragPosLightSpace = lightProjection * lightView * vec4(FragPos, 1.0f);
}
和片段着色器：
#version 130
struct Material
{
float shininess;
vec3 ambient;
vec3 diffuse;
vec3 specular;
};
struct DirLight
{
vec3 direction;
vec3 ambient;
vec3 diffuse;
vec3 specular;
};
struct PointLight
{
vec3 position;
float constant;
float linear;
float quadratic;
vec3 ambient;
vec3 diffuse;
vec3 specular;
};
struct SpotLight {
vec3 position;
vec3 direction;
float cutOff;
float outerCutOff;
float constant;
float linear;
float quadratic;
vec3 ambient;
vec3 diffuse;
vec3 specular;
};
struct AreaLight
{
vec3 position;
vec3 ambient;
vec3 diffuse;
vec3 specular;
};
out vec4 FragColor;
in vec3 FragPos;
in vec3 Normal;
in vec2 TexCoord;
in vec4 FragPosLightSpace;
uniform Material material;
uniform DirLight dirLight;
uniform PointLight pointLight;
uniform SpotLight spotLight;
uniform AreaLight areaLight;
uniform vec3 cameraPos;
uniform sampler2D texture1;
uniform sampler2D shadowMap;
float CalcShadow(vec4 FragPosLightSpace);
vec3 CalcDirLight(Material material, DirLight light, vec3 normal, vec3 viewDir);
vec3 CalcPointLight(Material material, PointLight light, vec3 normal, vec3 fragPos, vec3 viewDir);
vec3 CalcSpotLight(Material material, SpotLight light, vec3 normal, vec3 fragPos, vec3 viewDir);
vec3 CalcAreaLight(Material material, AreaLight light);
void main(void)
{
vec3 viewDir = normalize(cameraPos - FragPos);
vec3 finalLight = vec3(0.0f, 0.0f, 0.0f);
finalLight += CalcDirLight(material, dirLight, Normal, viewDir);
finalLight += CalcPointLight(material, pointLight, Normal, FragPos, viewDir);
finalLight += CalcSpotLight(material, spotLight, Normal, FragPos, viewDir);
finalLight += CalcAreaLight(material, areaLight);
FragColor = texture2D(texture1, TexCoord) * vec4(finalLight, 1.0f);
}
float CalcShadow(vec4 fragPosLightSpace)
{
// only actually needed when using perspective projection for the light
vec3 projCoords = fragPosLightSpace.xyz / fragPosLightSpace.w;
// projCoord is in [-1,1] range. Convert it ot [0,1] range.
projCoords = projCoords * 0.5 + 0.5;
float closestDepth = texture(shadowMap, projCoords.xy).r;
float currentDepth = projCoords.z;
float bias = 0.005f;
float shadow = currentDepth - bias > closestDepth ? 1.0 : 0.0;
return shadow;
}
vec3 CalcDirLight(Material material, DirLight light, vec3 normal, vec3 viewDir)
{
vec3 lightDir = normalize(-light.direction);
vec3 reflectDir = reflect(-lightDir, normal);
float ambientStrength = 1.0f;
float diffuseStrength = max(dot(normal, lightDir), 0.0);
float specularStrength = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);
float shadow = CalcShadow(FragPosLightSpace);
vec3 ambient = light.ambient * material.ambient * ambientStrength;
vec3 diffuse = (1.0f - shadow) * light.diffuse * material.diffuse * diffuseStrength;
vec3 specular = (1.0f - shadow) * light.specular * material.specular * specularStrength;
return (ambient + diffuse + specular);
}
vec3 CalcPointLight(Material material, PointLight light, vec3 normal, vec3 fragPos, vec3 viewDir)
{
vec3 lightDir = normalize(light.position - fragPos);
vec3 reflectDir = reflect(-lightDir, normal);
float ambientStrength = 1.0f;
float diffuseStrength = max(dot(normal, lightDir), 0.0);
float specularStrength = pow(max(dot(viewDir, reflectDir), 0.0f), material.shininess);
float attenuation = 1.0f / (1.0f + 0.01f*pow(length(light.position - fragPos), 2));
vec3 ambient = light.ambient * material.ambient * ambientStrength;
vec3 diffuse = light.diffuse * material.diffuse * diffuseStrength;
vec3 specular = light.specular * material.specular * specularStrength;
ambient *= attenuation;
diffuse *= attenuation;
specular *= attenuation;
return vec3(ambient + diffuse + specular);
}
vec3 CalcSpotLight(Material material, SpotLight light, vec3 normal, vec3 fragPos, vec3 viewDir)
{
vec3 lightDir = normalize(light.position - fragPos);
vec3 reflectDir = reflect(-lightDir, normal);
float ambientStrength = 0.05f;
float diffuseStrength = max(dot(normal, lightDir), 0.0);
float specularStrength = pow(max(dot(viewDir, reflectDir), 0.0f), material.shininess);
float attenuation = 1.0f / (1.0f + 0.01f*pow(length(light.position - fragPos), 2));
float theta = dot(lightDir, normalize(-light.direction));
float epsilon = light.cutOff - light.outerCutOff;
float intensity = clamp((theta - light.outerCutOff) / epsilon, 0.0f, 1.0f);
vec3 ambient = light.ambient * material.ambient * ambientStrength;
vec3 diffuse = light.diffuse * material.diffuse * diffuseStrength;
vec3 specular = light.specular * material.specular * specularStrength;
ambient *= attenuation * intensity;
diffuse *= attenuation * intensity;
specular *= attenuation * intensity;
return vec3(ambient + diffuse + specular);
}
vec3 CalcAreaLight(Material material, AreaLight light)
{
// return vec3(0.0f, 0.0f, 0.0f);
return vec3(2*material.ambient);
}
我想做的是将每种灯光类型分开到不同的着色器中，这样我就不用一个“ubershader”，而是有一个定向光着色器和一个聚光灯着色器等。这是个好主意吗？特别是我担心每次渲染调用多次切换着色器可能会很昂贵？
【问题讨论】：
-
视频里的物理很复杂，我觉得渲染器不复杂？也许你是对的，答案是广泛的（尽管我不知道）。在每个渲染过程中使用多个着色器是否被认为是一个好主意？还是过于依赖其他因素？
-
抱歉，您可能是指将水渲染为复杂的。让我通过说我将只使用刚体来简化问题，因此我只渲染一堆对象。我将使用行进立方体和 SPH 在我的引擎中加入水，但对于这个问题，我们可以假设它只是刚体。
-
这取决于很多因素，你应该开始评估你想要构建什么样的渲染管道以及为什么。你想坚持前向渲染还是前进+或延迟风格之一（香草、平铺、集群）？您的目标平台是什么，对您来说重要的是什么（性能与简单性），项目的范围是什么（如您在未来需要哪些功能）？打个比方，最简单的解决方案是您已经拥有的解决方案。如果不是问题，请不要修复它。