CODEWITHSUNDEEP
graphicsopengl-es
One Double
One Double

Reputation: 129

what format of pic can generate mimap in opengl-es

as the title, I used to use .dds, it did work,now I use type of .png, can it generate mipmap? Here functions what I am using: glTexImage2D(…).Or maybe gluBuild2DMipmaps(…) a better choice?

Upvotes: 0

Views: 70

Answers (1)

datenwolf
datenwolf

Reputation: 162174

DDS are an image format that contains precalculated mipmaps. As far as quality goes, precalculated mipmaps offer the best quality, since they can be downsampled offline with advanced filter kernels like Lancozs, without having to care about runtime efficiency.

PNG does not contain additional mipmap levels so you have to compute the mipmaps at runtime. You should however not use gluBuild2DMipmaps for this. For one this function is known to exhibit buggy behavior in certain conditions and furthermore it will unconditionally resample all images to power-of-2 dimensions, although since OpenGL-2 non power-of-2 dimensions are perfectly fine for texture images.

Instead you should load the base level image with glTexImage2D(…) and use glGenerateMipmap(…) (available since OpenGL-3) to build the mipmap image pyramid from there. If you don't use OpenGL-3, you can use the SGIS_generate_mipmap extension, if available.

However be advised that online mipmap generation may yield not as good results as offline generation.

Another possible approach would be the use of JPEG2000 images; the nature of JPEG2000 image encoding results in an image pyramid being readily available. OTOH JPEG2000 is very costly to encode and decode.

Upvotes: 1

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