skybox纹理未在opengl中显示

Question

我有一个简单的skybox。

#include <GL/glew.h>
#include <GL/freeglut.h>
#include <vector>
#include <iostream>

#include "texture.h"
#include "deviLoader.h"

using namespace std;

static std::vector<GLuint> textures;

class Skybox
{
private:
float x, y, z;
float width, height, length;
bool isBottomRequired;
void rearrange();
void loadTextures();
public:
Skybox() {};
Skybox(float x, 
        float y, 
        float z, 
        float width, 
        float height, 
        float length);
void renderSkybox();
void setBottom(bool required);
~Skybox() {};
};

我在方法devIL loadTextures中使用loadTextures库加载纹理。

void Skybox::loadTextures()
{
cout<<"SKYBOX: texture loading...";

Texture t;
LoadTexture(IL_BMP, "Back.bmp", &t);
textures.push_back(t.texID);

LoadTexture(IL_BMP, "Front.bmp", &t);
textures.push_back(t.texID);

LoadTexture(IL_BMP, "Bottom.bmp", &t);
textures.push_back(t.texID);

LoadTexture(IL_BMP, "Top.bmp", &t);
textures.push_back(t.texID);

LoadTexture(IL_BMP, "Left.bmp", &t);
textures.push_back(t.texID);

LoadTexture(IL_BMP, "Right.bmp", &t);
textures.push_back(t.texID);

/*
LoadTexture(IL_BMP, "Back.bmp", &t);
textures[0] = t.texID;
*/

cout<<"SUCCESS"<<endl;
}

其中函数loadTexture

void LoadTexture(ILenum FileType, char *filename, Texture *texture)
{
ilInit();
iluInit();

ilLoad(FileType, filename);

int err = ilGetError();
if (err != IL_NO_ERROR)
{
    const char* strError = iluErrorString(err);
    cout<<strError<<" - error during loading!"<<endl;
    return;
}

texture->width = ilGetInteger(IL_IMAGE_WIDTH);
texture->height = ilGetInteger(IL_IMAGE_HEIGHT);
texture->bpp = ilGetInteger(IL_IMAGE_BYTES_PER_PIXEL);

texture->imageData = ilGetData();

ilEnable(IL_CONV_PAL);

unsigned int type = ilGetInteger(IL_IMAGE_FORMAT);

glGenTextures(1, &texture->texID);
glBindTexture(GL_TEXTURE_2D, texture->texID);

gluBuild2DMipmaps(GL_TEXTURE_2D, texture->bpp, texture->width, texture->height,
    type, GL_UNSIGNED_BYTE, texture->imageData);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
}

在我的main.cpp中，我将skybox对象声明为全局变量，并在方法draw中呈现它。

Skybox skyBox;
.....
//part of method draw
if (selected[7] == 1) {
    glDisable(GL_FOG);
    glEnable(GL_TEXTURE_2D);
    glPushMatrix();
        glTranslatef(-0.2, 4, 2.3);
        glScalef(0.15, 0.2, 0.19);
        skyBox.renderSkybox();
    glPopMatrix();
    glDisable(GL_TEXTURE_2D);
    if (selected[6] == 1)
        glEnable(GL_FOG);
}

renderSkybox法

void Skybox::renderSkybox()
{
glBindTexture(GL_TEXTURE_2D, textures[0]);
glBegin(GL_QUADS);
    glTexCoord2f(1.0, 0.0); glVertex3f(x + width, y, z);
    glTexCoord2f(1.0, 1.0); glVertex3f(x + width, y + height, z);
    glTexCoord2f(0.0, 1.0); glVertex3f(x, y + height, z);
    glTexCoord2f(0.0, 0.0); glVertex3f(x, y, z);
glEnd();

glBindTexture(GL_TEXTURE_2D, textures[1]);
glBegin(GL_QUADS);
    glTexCoord2f(1.0f, 0.0f); glVertex3f(x, y, z + length);
    glTexCoord2f(1.0f, 1.0f); glVertex3f(x, y + height, z + length);
    glTexCoord2f(0.0f, 1.0f); glVertex3f(x + width, y + height, z + length);
    glTexCoord2f(0.0f, 0.0f); glVertex3f(x + width, y,z + length);
glEnd();

if (isBottomRequired)
{
    glBindTexture(GL_TEXTURE_2D, textures[2]);
    glBegin(GL_QUADS);
        glTexCoord2f(1.0f, 0.0f); glVertex3f(x, y,z);
        glTexCoord2f(1.0f, 1.0f); glVertex3f(x, y,z + length);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(x + width, y,z + length);
        glTexCoord2f(0.0f, 0.0f); glVertex3f(x + width, y,z);
    glEnd();
}

glBindTexture(GL_TEXTURE_2D, textures[3]);
glBegin(GL_QUADS);
    glTexCoord2f(0.0f, 1.0f); glVertex3f(x + width, y + height, z);
    glTexCoord2f(0.0f, 0.0f); glVertex3f(x + width, y + height, z + length);
    glTexCoord2f(1.0f, 0.0f); glVertex3f(x, y + height,z + length);
    glTexCoord2f(1.0f, 1.0f); glVertex3f(x, y + height,z);
glEnd();

glBindTexture(GL_TEXTURE_2D, textures[4]);
glBegin(GL_QUADS);
    glTexCoord2f(1.0f, 1.0f); glVertex3f(x, y + height,z);
    glTexCoord2f(0.0f, 1.0f); glVertex3f(x, y + height,z + length);
    glTexCoord2f(0.0f, 0.0f); glVertex3f(x, y,z + length);
    glTexCoord2f(1.0f, 0.0f); glVertex3f(x, y,z);
glEnd();

glBindTexture(GL_TEXTURE_2D, textures[5]);
glBegin(GL_QUADS);
    glTexCoord2f(0.0f, 0.0f); glVertex3f(x + width, y,z);
    glTexCoord2f(1.0f, 0.0f); glVertex3f(x + width, y,z + length);
    glTexCoord2f(1.0f, 1.0f); glVertex3f(x + width, y + height,z + length);
    glTexCoord2f(0.0f, 1.0f); glVertex3f(x + width, y + height,z);
glEnd();
};

当我画其他物体时，可以看到天窗看起来是黑色的。

有什么问题吗？为什么是黑色的？

编辑，我已经添加了项目，以防有人决定用更多的细节来研究问题。有项目和glm，assimp，魔鬼，自由职业者。项目尚未完成，但应该能工作。

http://www.filedropper.com/task

Answer 1

绘制天窗有两种策略：

• 使用天窗“清除”：你画天空框作为你的场景中的第一件事。在绘制skybox调用glDisable(GL_DEPTH_TEST); glDepthMask(GL_FALSE);之前，然后绘制skybox并根据需要重新启用深度测试(glEnable(GL_DEPTH_TEST))和深度写入(glDepthMask(GL_FALSE))
• 在最后一次不透明之后，但在混合几何图形之前绘制天框(需要支持深度夹紧)。清除场景，将深度缓冲区清除到(pow(2, b)-1.)/pow(2, b)，其中b是深度缓冲区的位深度。像往常一样画出不透明的场景。启用深度夹紧和深度测试，将深度测试函数设置为更大或等于(glDepthFunc(GL_GEQUAL))，并设置一个投影，或缩放天窗，这样天空盒四元将始终保持在后面的远剪裁平面。由于深度夹紧所生成的片段深度，所有的be 1.0都通过了深度测试，仅在屏幕的那些区域呈现skybox，而不是其他几何学所覆盖的区域。