osg Mipmap Generation

the_mercury

如下是一段OpenGL 自动生成Mipmap的代码:

1. Image image;
   
2. 
   
3. typedef GLuint TextureID;
   
4. 
   
5. TextureID texID;
   
6. GLint max_texture_max_anisotropy = 0;
   
7. //load a image
   
8. image = load_image("image.jpg");//asume a jpg file
   
9. 
   
10. glGenTextures(1,&texID);
    
11. glBindTexture(GL_TEXTURE_2D,texID);
    
12. glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    
13. glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIP_LINEAR);
    
14. glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP);
    
15. glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP);
    
16. 
    
17. glGetTexParameteri(GL_TEXTURE_2D,GL_MAX_TEXTURE_MAX_ANISOTROPY,&max_texture_max_anisotropy);
    
18. glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAX_ANISOTROPY,max_texture_max_anisotropy);
    
19. 
    
20. glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAX_LEVEL,8);//these two parameters control the range of mipmap
    
21. glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_BASE_LEVEL,0);//to generate
    
22. 
    
23. #if USE_GLU_BUILD_MIPMAP
    
24. gluBuild2DMipmaps(GL_TEXTURE_2D,image.getFormat(),image.getWidth(),image.getHeight(),image.getFormat(),image.getType(),image.getData());
    
25. #else
    
26. glTexParameteri(GL_TEXTURE_2D,GL_GENERATE_MIPMAP,GL_TRUE);
    
27. glTexImage2D(GL_TEXTURE_2D,0,image.getFormat(),image.getWidth(),image.getHeight(),0,image.getFormat(),image.getType(),image.getData());
    
28. glTexParameteri(GL_TEXTURE_2D,GL_GENERATE_MIPMAP,GL_FALSE);
    
29. #endif
    

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在osg之中自动生成Mipmap(不是我们生成好后再一层一层设置的那种)是怎么完成的呀？还有GL_TEXTURE_BASE_LEVEL,GL_TEXTURE_MAX_LEVEL这两个参数是怎么设置的?

array

自动mipmap只要设置setFilter为带有MIPMAP的类型就可以了，至于GL_TEXTURE_BASE_LEVEL和GL_TEXTURE_MAX_LEVEL并没有做对应的实现，因为实际意义比较有限