opengl学习(1): 天空盒

使用一个立方体纹理，由六张图片拼成一个天空盒，然后让它做沿Y轴逆时针转动。

#include "TEST_Skybox.h"
#include 

using namespace std;

static GLint skybox_rotate_loc = 0;

TEST_FUNC_INIT(Skybox)
{
    GLuint vao;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);


    const GLfloat cube_vertices[] =
    {
        -1.0f, -1.0f, -1.0f,
        -1.0f, -1.0f,  1.0f,
        -1.0f,  1.0f, -1.0f,
        -1.0f,  1.0f,  1.0f,
        1.0f, -1.0f, -1.0f,
        1.0f, -1.0f,  1.0f,
        1.0f,  1.0f, -1.0f,
        1.0f,  1.0f,  1.0f
    };

    const GLushort cube_indices[] =
    {
        0, 1, 2, 3, 6, 7, 4, 5,         // First strip
        2, 6, 0, 4, 1, 5, 3, 7          // Second strip
    };

    GLuint cube_vbo;
    glGenBuffers(1, &cube_vbo);
    glBindBuffer(GL_ARRAY_BUFFER, cube_vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(cube_vertices), cube_vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);
    glEnableVertexAttribArray(0);

    GLuint cube_element_buffer;
    glGenBuffers(1, &cube_element_buffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, cube_element_buffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(cube_indices), cube_indices, GL_STATIC_DRAW);

    GLuint skybox_prog = createShader("TEST_Skybox.vert", "TEST_Skybox.frag");
    skybox_rotate_loc = glGetUniformLocation(skybox_prog, "tc_rotate");

    // 加载立方体纹理
    TextureInfo infoPX = getRawTextureFromFile("lf1.png");
    TextureInfo infoNX = getRawTextureFromFile("rt1.png");
    TextureInfo infoPY = getRawTextureFromFile("up1.png");
    TextureInfo infoNY = getRawTextureFromFile("dn1.png");
    TextureInfo infoPZ = getRawTextureFromFile("ft1.png");
    TextureInfo infoNZ = getRawTextureFromFile("bk1.png");

    GLuint cubTex;
    glGenTextures(1, &cubTex);
    glBindTexture(GL_TEXTURE_CUBE_MAP, cubTex);
    glTexStorage2D(GL_TEXTURE_CUBE_MAP, 1, GL_RGBA8, (GLsizei)infoPX.width, (GLsizei)infoPX.height);
    glTexSubImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X, 0, 0, 0, (GLsizei)infoPX.width, (GLsizei)infoPX.height, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*)infoPX.data);
    glTexSubImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_X, 0, 0, 0, (GLsizei)infoNX.width, (GLsizei)infoNX.height, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*)infoNX.data);
    glTexSubImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Y, 0, 0, 0, (GLsizei)infoPY.width, (GLsizei)infoPY.height, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*)infoPY.data);
    glTexSubImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, 0, 0, 0, (GLsizei)infoNY.width, (GLsizei)infoNY.height, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*)infoNY.data);
    glTexSubImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_Z, 0, 0, 0, (GLsizei)infoPZ.width, (GLsizei)infoPZ.height, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*)infoPZ.data);
    glTexSubImage2D(GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, 0, 0, 0, (GLsizei)infoNZ.width, (GLsizei)infoNZ.height, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*)infoNZ.data);

    free(infoPX.data);
    free(infoNX.data);
    free(infoPY.data);
    free(infoNY.data);
    free(infoPZ.data);
    free(infoNZ.data);

    cout << glGetError() << endl;
}

TEST_FUNC_LOOP(Skybox)
{
    static const unsigned int start_time = getCurTime();
    float t = float(getCurTime() - start_time) / float(0x3FFF);
    static const vmath::vec3 X(1.0f, 0.0f, 0.0f);
    static const vmath::vec3 Y(0.0f, 1.0f, 0.0f);
    static const vmath::vec3 Z(0.0f, 0.0f, 1.0f);

    vmath::mat4 tc_matrix(vmath::mat4::identity());

    glClearColor(0.0f, 0.25f, 0.3f, 1.0f);
    glClearDepth(1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glDisable(GL_CULL_FACE);


    glEnable(GL_TEXTURE_CUBE_MAP_SEAMLESS);

    float aspect = float(480) / 640.0f;

    tc_matrix = vmath::rotate(80.0f * 3.0f * t, Y);
//    cout << getCurTime() - start_time <
    tc_matrix = vmath::perspective(35.0f, 1.0f / aspect, 0.1f, 100.0f) * tc_matrix;

    glUniformMatrix4fv(skybox_rotate_loc, 1, GL_FALSE, tc_matrix);
    glDrawElements(GL_TRIANGLE_STRIP, 8, GL_UNSIGNED_SHORT, NULL);
    glDrawElements(GL_TRIANGLE_STRIP, 8, GL_UNSIGNED_SHORT, (GLvoid*)(8 * sizeof(GLushort)));
//    cout << glGetError() << endl;
    return false;
}