c++ - glLightfv GL_POSITION GL_LINEAR_ATTENUATION glsl OpenGL3 或 OpenGL4(位置光)

Question

好吧，我又迷失在大量教程中，这些教程似乎将旧的 GL 版本与 GL3 和 4 混为一谈。大多数教程都使用已弃用的代码，我正在寻找合适的 OpenGL3，或者甚至更好的 OpenGL4 替代品对于这个伪代码:

GLfloat LightRadius=0.5f; //or whatever value.
glLightf(NumLights, GL_LINEAR_ATTENUATION, LightRadius);
GLfloat light_position[] = { LightLoc.X,LightLoc.Y, LightLoc.Z, 1 }; //World space location
glLightfv(NumLights, GL_POSITION, light_position);

用于 phong 照明

vs 可能看起来像这样:

#version 330
layout (location = 0) in vec3 Position;
layout (location = 1) in vec3 PositionNormals;

uniform mat4 projMat;
uniform mat4 viewMat;
uniform mat4 modelMat;

out vec3 vposition;
out vec3 vnormal;

out mat4 vprojMat;
out mat4 vviewMat;
out mat4 vmodelMat;

void main(void)
{

    vprojMat    = projMat; // from what I understood I need those in the fs as well..?
    vviewMat    = viewMat;
    vmodelMat   = modelMat;

    vposition   = vec3(viewMat * modelMat * vec4 (Position, 1.0));
    vnormal     = vec3(viewMat * modelMat * vec4 (PositionNormals, 0.0));

    gl_Position     = projMat * vec4(vposition_eye, 1.0);

}

和 fs:

in vec3 vposition;
in vec3 vnormal;

in mat4 vprojMat;
in mat4 vviewMat;
in mat4 vmodelMat;

struct LightInfo                                                           
{  
    vec3 LightLocation;                                                                   
    vec3 DiffuseLightColor;
    vec3 AmbientLightColor;
    vec3 SpecularLightColor;
    float AmbientLightIntensity;
    float SpecularLightIntensity;
    float LightRadius;
};
uniform LightInfo gLight;                                         

out vec4 FragColor; 

void main (void)  
{  
    //Diffuse Lighting

    // and here I am lost. Was trying to do in eyespace, but the light seems to float more somewhere instead of having a fixed position.

    vec3 light_position = ??? gLight.LightLocation; // probably normalized?

    float dot_prod = ??? 
    dot_prod = max (dot_prod, 0.0);
    vec3 diffuse_intensity = gLight.DiffuseLightColor * dot_prod; // final diffuse intensity


    FragColor=diffuse_intensity;
}

这个想法相当简单，只是房间内的一盏灯根据任意半径以给定的衰减向所有方向(如太阳)照射。我似乎无法找出它背后的数学原理。如果这是一个愚蠢的问题，请原谅我，但我读得越多，我就越困惑。我知道我需要计算漫射光的点、表面的朝向(法线)以及从表面到光的方向，但我无法将它们放在一起。

Answer 1

您应该在同一坐标系中拥有所有顶点和灯光数据。如果你在世界坐标中发送光的位置，你也应该用世界空间中的法线做点积。在性能方面，最好在眼睛/相机空间中发送光线。为此，您应该像这样调用 glLightfv:

// The 4th component of the light position should be 1, because it's a position, not a direction
GLfloat light_position[] = { LightLoc.X,LightLoc.Y, LightLoc.Z, 1 }; //World space location
// TODO: Change to eye space multiplying by the inverse of the modelView matrix
Matrix4 invModelView;
inverseOrtho(viewMatrix * modelMatrix, invModelView);
transformVector4(light_position, invModelView);
glLightfv(NumLights, GL_POSITION, light_position);    // Send light in eye space

如果眼睛空间中有灯光，像素着色器比计算世界空间中的所有灯光更简单。

void main (void)  
{  
    //Diffuse Lighting

    vec3 light_position = gLight.LightLocation;    // Light position in eye space

    // calculate the light direction from the light to the vertex being iluminated
    float dot_prod = dot((vposition - light_position).normalize(), vnormal);
    dot_prod = max (dot_prod, 0.0);
    vec3 diffuse_intensity = gLight.DiffuseLightColor * dot_prod; // final diffuse intensity

    FragColor=diffuse_intensity;
}