OpenGL学习20——立方体贴图

2021-07-08  本文已影响0人  蓬篙人

立方体贴图(Cubemaps)

1. 创建立方体贴图

unsigned int textureID;
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);
纹理目标 方向
GL_TEXTURE_CUBE_MAP_POSITIVE_X
GL_TEXTURE_CUBE_MAP_NEGATIVE_X
GL_TEXTURE_CUBE_MAP_POSITIVE_Y
GL_TEXTURE_CUBE_MAP_NEGATIVE_Y
GL_TEXTURE_CUBE_MAP_POSITIVE_Z
GL_TEXTURE_CUBE_MAP_NEGATIVE_Z
int width, height, nrChannels;
unsigned char* data;
for(unsigned int i = 0; i < texture_faces.size(); i++)
{
    data = stb_load(texture_faces[i].c_str(), & width, &height, &nrChannels, 0);
    glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
}
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
in vec3 textureDir;   // 方向矢量:3D纹理的坐标
unfirom samplerCube cubemap;   // 立方体贴图纹理取样器

void main()
{
    FragColor = texture(cubemap, textureDir);
}

2. 天空盒(Skybox)

2.1 加载天空盒

unsigned int loadCubemap(std::vector<std::string> faces)
{
    unsigned int textureID;
    glGenTextures(1, &textureID);
    glBindTexture(GL_TEXTURE_CUBE_MAP, textureID);
    int width, height, nrChannels;
    unsigned char* data;
    for(unsigned int i = 0; i < faces.size(); i++)
    {
        unsigned char* data = stbi_load(faces[i].c_str(), & width, &height, &nrChannels, 0);
        if(data)
        {
            glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
            stbi_image_free(data);
        }
        else
        {
            std::cout << "Cubemap failed to load at path: " << faces[i] << std::endl;
            stbi_image_free(data);
        }
    }
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

    return textureID;
}
std::vector<std::string> faces = {
    "right.jpg",
    "left.jpg",
    "top.jpg",
    "bottom.jpg",
    "front.jpg",
    "back.jpg"
};
unsigned int cubemapTexture = loadCubemap(faces);

2.2 显示天空盒

#version 330 core
layout (location = 0) in vec3 aPos;

out vec3 TexCoords;

uniform mat4 projection;
uniform mat4 view;

void main()
{
    TexCoords = aPos;
    gl_Position = projection * view * vec4(aPos, 1.0);
}
#version 330 core
out vec4 FragColor;

in vec3 TexCoords;

uniform samplerCube skybox;

void main()
{
    FragColor = texture(skybox, TexCoords);
}
glDepthMask(GL_FALSE);
skyboxShader.use();
// ... 设置视矩阵和投影矩阵
glBindVertexArray(skyboxVAO);
glBindTexture(GL_TEXTURE_CUBE_MAP, cubemapTexture);
glDrawArrays(GL_TRIANGLES, 0, 36);
glDepthMask(GL_TRUE);
// ... 绘制剩下的场景
glm::vec4 view = glm::mat4(glm::mat3(camera.GetViewMatrix()));
void main()
{
    TexCoords = aPos;
    vec4 pos = projection * view * vec4(aPos, 1.0);
    gl_Position = pos.xyww;
}

3. 环境映射(Environment mapping)

3.1 反射

#version 330 core
out vec4 FragColor;

in vec3 Normal;
in vec3 Position;

uniform vec3 cameraPos;
uniform samplerCube skybox;

void main()
{
    vec3 I = normalize(Position - cameraPos);
    vec3 R = reflect(I, normalize(Normal));
    FragColor = vec4(texture(skybox, R).rgb, 1.0);
}
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec2 aNormal;

out vec3 Normal;
out vec3 Position;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;

void main()
{
    Normal = mat3(transpose(inverse(model))) * aNormal;
    Position = vec3(model * vec4(aPos, 1.0));
    gl_Position = projection * view * vec4(Position, 1.0);
}
glBindVertexArray(cubeVAO);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_CUBE_MAP, cubemapTexture);
glDrawArrays(GL_TRIANGLES, 0, 36);

3.2 折射(Refraction)

材质 折射率
空气 1.00
1.33
1.309
玻璃 1.52
钻石 2.42
void main()
{
    float ratio = 1.00 / 1.52;
    vec3 I = normalize(Position - cameraPos);
    vec3 R = refract(I, normalize(Normal), ratio);
    FragColor = vec4(texture(skybox, R).rgb, 1.0);
}
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