4 replies to this topic

[Yours3!f]

Hi,

I'm trying to sample a certain mipmap level of a mipmapped texture. How do I do that?

  //do the downsampling
  tex.bind();
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
  glGenerateMipmap( GL_TEXTURE_2D );

  //process the half res texture
  glViewport( 0, 0, o->conf.SCREEN_WIDTH / 2, o->conf.SCREEN_HEIGHT / 2 );

  half_fbo.bind();
  shader->bind();

  shader->pass_m4x4( o->ppl.get_projection_matrix(), "proj" );
  shader->pass_m4x4( o->ppl.get_model_view_matrix(), "modelview" );
  shader->pass_int( 0, "texture0" );

  tex.bind();
//how do I select the desired mipmap level here?
  quad.render();

  shader->unbind();
  half_fbo.unbind();

Best regards,
Yours3!f

Edited by Yours3!f, 31 August 2012 - 01:48 PM.

[Yours3!f]

duplicate

Edited by Yours3!f, 31 August 2012 - 01:47 PM.

[dpadam450]

http://www.opengl.org/sdk/docs/man/xhtml/glTexParameter.xml

MIN_LOD, MAX_LOD, BASE_LEVEL, MAX_LEVEL

Setting 2 of those should do it.

[mhagain]

Since you're using GLSL you don't need to respecify any glTexParameter stuff; just use textureLod to sample the specific level you want: http://www.opengl.org/wiki/GLSL_Sampler#Lod_texture_access

[Yours3!f]

thank you both, I think I'll stick to the GLSL version, this seems more convenient.