Imagination PowerVR SDK Blog

Skybox & PVRTC


#1

Hi,


    It seems when compress skybox textures to pvrtc 4bpp all mipmap, no matter i choose “Add Border” or not, there always will be ugly edges… I also checked the offical skybox demo, and found all the pvr files are no borders. and i am sure i called


Code:

    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    myglTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
    myglTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);



can anyone tell me how to compress skybox textures to pvrtc format?


#2

and when i use RGBA8888 pvr, everything works fine.


#3

Hi Rubbio,





What sort of “ugly edges” can you see? If you view the cube map in the TexTool GUI editor, can you see the same artifacts along the edges between the 6 faces of the cube map, or do they only appear in your application?


As PVRTC is lossy texture compression, there will be some degradation in quality, but this is usually negligible when compared to the performance gain of using compressed textures. Using an 8bpp format will always provide a better visual quality that the 4bpp, but you have to decide if the improved aesthetics are worth the additional cost.





If you send a ZIP file of your uncompressed and compressed cube map to devtech@imgtec.com I can take a look at them for you.