使用延迟渲染的阴影贴图(OpenGL)

GLuint gBuffer;
glGenFramebuffers(1, &gBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, gBuffer);

GLuint gPosition, gNormal, gColorSpec;

// 位置纹理
glGenTextures(1, &gPosition);
glBindTexture(GL_TEXTURE_2D, gPosition);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB16F, screenWidth, screenHeight, 0, GL_RGB, GL_FLOAT, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, gPosition, 0);

// 法线纹理
glGenTextures(1, &gNormal);
glBindTexture(GL_TEXTURE_2D, gNormal);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB16F, screenWidth, screenHeight, 0, GL_RGB, GL_FLOAT, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, gNormal, 0);

// 颜色+镜面纹理
glGenTextures(1, &gColorSpec);
glBindTexture(GL_TEXTURE_2D, gColorSpec);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, screenWidth, screenHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_2D, gColorSpec, 0);

// 告诉OpenGL我们将使用这些附件
GLuint attachments[3] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2 };
glDrawBuffers(3, attachments);

// 创建并绑定深度缓冲
GLuint depthBuffer;
glGenRenderbuffers(1, &depthBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, depthBuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, screenWidth, screenHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthBuffer);

// 检查帧缓冲完整性
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    std::cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete!" << std::endl;
glBindFramebuffer(GL_FRAMEBUFFER, 0);

glBindFramebuffer(GL_FRAMEBUFFER, gBuffer);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);

// 渲染场景中的每个物体
for(auto& object : sceneObjects) {
    // 设置模型矩阵、视图矩阵、投影矩阵
    // ...

    // 绑定VAO并绘制物体
    glBindVertexArray(object.vao);
    glDrawElements(GL_TRIANGLES, object.indexCount, GL_UNSIGNED_INT, 0);
}

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// 设置视口
glViewport(0, 0, screenWidth, screenHeight);

// 使用着色器程序
shader.use();

// 绑定G-Buffer纹理
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, gPosition);
shader.setInt("gPosition", 0);

glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, gNormal);
shader.setInt("gNormal", 1);

glActiveTexture(GL_TEXTURE2);
glBindTexture(GL_TEXTURE_2D, gColorSpec);
shader.setInt("gColorSpec", 2);

// 渲染一个全屏四边形
renderQuad();

// 在片段着色器中进行光照计算
// ...

// 设置光源的视口和投影矩阵
// ...

// 渲染场景到光源深度贴图
glBindFramebuffer(GL_FRAMEBUFFER, lightDepthMapFBO);
glClear(GL_DEPTH_BUFFER_BIT);
glCullFace(GL_FRONT);

for(auto& object : sceneObjects) {
    // 设置模型矩阵、光源视图矩阵、光源投影矩阵
    // ...

    // 绑定VAO并绘制物体
    glBindVertexArray(object.vao);
    glDrawElements(GL_TRIANGLES, object.indexCount, GL_UNSIGNED_INT, 0);
}

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glCullFace(GL_BACK);

// 片段着色器
#version 330 core
out vec4 FragColor;

in vec2 TexCoords;

uniform sampler2D gPosition;
uniform sampler2D gNormal;
uniform sampler2D gColorSpec;
uniform sampler2D shadowMap;

uniform vec3 viewPos;
uniform vec3 lightPos;
uniform mat4 lightSpaceMatrix;

float ShadowCalculation(vec4 fragPosLightSpace) {
    // 执行透视除法
    vec3 projCoords = fragPosLightSpace.xyz / fragPosLightSpace.w;
    projCoords = projCoords * 0.5 + 0.5;
    float closestDepth = texture(shadowMap, projCoords.xy).r;
    float currentDepth = projCoords.z;
    float shadow = currentDepth > closestDepth ? 1.0 : 0.0;
    return shadow;
}

void main() {
    // 从G-Buffer中获取位置、法线和颜色
    vec3 FragPos = texture(gPosition, TexCoords).rgb;
    vec3 Normal = texture(gNormal, TexCoords).rgb;
    vec3 Diffuse = texture(gColorSpec, TexCoords).rgb;

    // 计算光照
    vec3 lighting = vec3(0.0);
    vec3 ambient = 0.1 * Diffuse;
    vec3 viewDir = normalize(viewPos - FragPos);
    vec3 lightDir = normalize(lightPos - FragPos);

    // 计算漫反射
    float diff = max(dot(Normal, lightDir), 0.0);
    vec3 diffuse = diff * Diffuse;

    // 计算镜面高光
    vec3 reflectDir = reflect(-lightDir, Normal);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
    vec3 specular = vec3(0.2) * spec;

    // 计算阴影
    vec4 fragPosLightSpace = lightSpaceMatrix * vec4(FragPos, 1.0);
    float shadow = ShadowCalculation(fragPosLightSpace);

    lighting = (ambient + (1.0 - shadow) * (diffuse + specular));

    FragColor = vec4(lighting, 1.0);
}