c++ - OpenGL - 制作跟随相机的点光源

Question

我目前正在创建一个 3D 场景，我想知道创建跟随相机的点光源的最佳方法是什么。到目前为止我的代码如下:

顶点着色器:

// Materials
uniform vec3 materialAmbient;
uniform vec3 materialDiffuse;
uniform vec3 materialSpecular;
uniform float materialShininess;

uniform float att_quadratic = 0.1;

// Lights
struct AMBIENT
{   
    vec3 color;
};
struct DIRECTIONAL
{   
    vec3 direction;
    vec3 diffuse;
};
struct POINT
{   int on;
    int frag;
    vec3 position;
    vec3 diffuse;
    vec3 specular;
};

uniform AMBIENT lightAmbient;
uniform DIRECTIONAL lightDir;
uniform POINT lightPoint1, lightPoint2, lightPoint3;

layout (location = 0) in vec3 aVertex;
layout (location = 2) in vec3 aNormal;
layout (location = 3) in vec2 aTexCoord;

// Output (sent to Fragment Shader)
out vec4 color;
out vec4 position;
out vec4 normal;
out vec2 texCoord;
out float gravelFactor;     // gravelFactor is 1 within the gravel circle and 0 outside the circle

vec4 compAmbient(vec3 material, AMBIENT light)
{
    return vec4(material * light.color, 1);
}

vec4 compDirectional(vec3 material, DIRECTIONAL light)
{
    vec3 L = normalize(mat3(matrixView) * light.direction).xyz;
    float NdotL = dot(normal.xyz, L);
    if (NdotL > 0)
        return vec4(light.diffuse * material * NdotL, 1);
    else
        return vec4(0, 0, 0, 1);
}

vec4 compPoint(vec3 materialDiffuse, vec3 materialSpecular, float materialShininess, POINT light)
{
    vec4 result = vec4(0, 0, 0, 1);

    // diffuse
    vec3 L = normalize(matrixView * vec4(light.position, 1) - position).xyz;
    float NdotL = dot(L, normal.xyz);
    if (NdotL > 0)
        result += vec4(light.diffuse * materialDiffuse, 1) * NdotL;

    // specular
    vec3 V = normalize(-position.xyz);
    vec3 R = reflect(-L, normal.xyz);
    float RdotV = dot(R, V);
    if (NdotL > 0 && RdotV > 0)
        result += vec4(light.specular * materialSpecular * pow(RdotV, materialShininess), 1);

    //attentuation
    float dist = length(matrixView * vec4(light.position, 1) - position); 
    float att = 1 / (att_quadratic * dist * dist); 

    return result * att;
}

void main(void) 
{
    // calculate position & normal
    position = matrixModelView * vec4(aVertex, 1.0);
    gl_Position = matrixProjection * position;
    normal = vec4(normalize(mat3(matrixModelView) * aNormal), 1);

    // calculate texture coordinate
    texCoord = aTexCoord;

    // calculate the colour
    color = vec4(0, 0, 0, 0);

    // ambient light
    color += compAmbient(materialAmbient, lightAmbient);

    // directional lights
    color += compDirectional(materialDiffuse, lightDir);

    // point lights
    if (lightPoint1.on == 1 && lightPoint1.frag == 0)
        color += compPoint(materialDiffuse, materialSpecular, materialShininess, lightPoint1);
    if (lightPoint2.on == 1 && lightPoint2.frag == 0)
        color += compPoint(materialDiffuse, materialSpecular, materialShininess, lightPoint2);
    if (lightPoint3.on == 1 && lightPoint3.frag == 0)
        color += compPoint(materialDiffuse, materialSpecular, materialShininess, lightPoint3);

    // calculation of the gravelFactor:
    // 0 outside the 8-unit radius from the center
    // 1 within 7 units from the centre
    // between 0 and 1 at the border zone
    gravelFactor = clamp(-length(aVertex.xz) + 8, 0, 1);
}

片段着色器:

// input variables
in vec4 color;
in vec4 position;
in vec4 normal;
in vec2 texCoord;
in float gravelFactor;

// output variable
out vec4 outColor;

// uniforms - material parameters
uniform vec3 materialAmbient;
uniform vec3 materialDiffuse;
uniform vec3 materialSpecular;
uniform float materialShininess;

uniform float att_quadratic = 0.1;

// This uniform variable may be used to take different actions for the terrain and not-terrain
uniform int terrain;

// view matrix (needed for lighting)
uniform mat4 matrixView;

struct POINT
{   int on;
    int frag;
    vec3 position;
    vec3 diffuse;
    vec3 specular;
};

uniform POINT lightPoint1, lightPoint2, lightPoint3;

vec4 compPoint(vec3 materialDiffuse, vec3 materialSpecular, float materialShininess, POINT light)
{
    vec4 result = vec4(0, 0, 0, 1);

    // diffuse
    vec3 L = normalize(matrixView * vec4(light.position, 1) - position).xyz;
    float NdotL = dot(L, normal.xyz);
    if (NdotL > 0)
        result += vec4(light.diffuse * materialDiffuse, 1) * NdotL;

    // specular
    vec3 V = normalize(-position.xyz);
    vec3 R = reflect(-L, normal.xyz);
    float RdotV = dot(R, V);
    if (NdotL > 0 && RdotV > 0)
        result += vec4(light.specular * materialSpecular * pow(RdotV, materialShininess), 1);

    //attentuation
    float dist = length(matrixView * vec4(light.position, 1) - position); 
    float att = 1 / (att_quadratic * dist * dist); 

    return result * att;
}

// Texture Samplers
uniform sampler2D textureGrass;
uniform sampler2D textureGravel;
uniform sampler2D texture;
uniform sampler2D bumpmap;
uniform sampler2D textureNormal;

vec4 bump_normal = texture(textureNormal, texCoord.st) * 2 - 1; 

void main(void) 
{
    outColor = color;

    if (lightPoint1.on == 1 && lightPoint1.frag == 1)
        outColor += compPoint(materialDiffuse, materialSpecular, materialShininess, lightPoint1);
    if (lightPoint2.on == 1 && lightPoint2.frag == 1)
        outColor += compPoint(materialDiffuse, materialSpecular, materialShininess, lightPoint2);
    if (lightPoint3.on == 1 && lightPoint3.frag == 1)
        outColor += compPoint(materialDiffuse, materialSpecular, materialShininess, lightPoint3);

    if (terrain == 1)
    {
        // Rendering Terrain
        // Terrain is a mix of the Grass and Gravel texture
        outColor *= mix(texture(textureGrass, texCoord.st), texture(textureGravel, texCoord.st), gravelFactor);
    }
    else
    {
        outColor *= texture(texture, texCoord.st) + bump_normal;
    }
}

还有我的点光源声明:

//setup point light1
glUniform1i(glGetUniformLocation(idProg, "lightPoint1.on"), 1);
glUniform1i(glGetUniformLocation(idProg, "lightPoint1.frag"), 1);
glUniform3f(glGetUniformLocation(idProg, "lightPoint1.position"), 0, 3.1, 0.0);
glUniform3f(glGetUniformLocation(idProg, "lightPoint1.diffuse"), 1.0, 0.0, 0.0);
glUniform3f(glGetUniformLocation(idProg, "lightPoint1.specular"),  1.0, 0.0, 0.0);

解决此问题的最佳方法是什么？灯光的位置应该在主代码中还是在着色器中更改？我怎么能这样做？

Answer 1

我肯定会在您的主代码中更改灯光位置，然后将其传递给您的着色器。

例如，您更改位置的代码如下所示:

//called whenever you redraw your scene
void render() 
{
    //or however you want to position the light relative to your camera
    glUniform3f
        (
        glGetUniformLocation(idProg, "lightPoint1.position"), 
        get_camera_pos_x(), 
        get_camera_pos_y(), 
        get_camera_pos_z()
        );
    glUniform3f
        (            
        glGetUniformLocation(idProg, "lightPoint1.direction"), 
        get_camera_dir_x(), 
        get_camera_dir_y(), 
        get_camera_dir_z()
        )
    //...rest of your drawing code...
}

这样做的主要优点是消除了冗余计算。如果您让顶点着色器根据您的相机位置更新灯光位置，它会起作用，但您会在每一帧重复多次计算。请记住，顶点着色器会在您绘制的每个 顶点上执行。如果每次都相同，则无需重新计算光在每个顶点上的位置。

评论中每个 OP 的更新:OP 表示他希望能够使用相机改变光线的方向，就像手电筒一样。为此，您需要在着色器中为您的灯光结构添加一个额外的制服。我在上面将其称为“方向”(规范化的 vec3)。然后，您可以在主代码中计算相机的方向，并像往常一样将其传递给着色器。你在着色器中用它做什么取决于你，但是this tutorial可能有帮助