Access mipmap level in fragment shader [OpenGL ES 2.0]

[meanderix]

Hello,

I know that I can adjust the mipmap level when sampling a texture in a fragment shader by using texture2D with the additional parameter bias.

However, by using 'bias' you're implicitly adding a bias to the current level-of-detail. I want to be able to control the level-of-detail and thus I would like to override any level-of-detail computed within the hardware itself.

What are my options here?

[Alfonse Reinheart]

Default GLSL ES 2.0 doesn't have this ability. It does have LOD texturing functions, but those can only be used in vertex shaders.

However, the EXT_shader_texture_lod allows you to use versions of these functions in fragment shaders. I have no idea how widely this is available.