Early days yet but I thought I'd share some shots of my progress.
http://imgur.com/a/fGgeW
{nofragment 1surfaceFlags surf_NoAreasstageprogram skyboxmergenoshadows 1envmap linear env/gskydome_pxskyScale { 1, 1, 1, 1.0 }transmap scale( models/mapobjects/skies/hlchumpskyclouds, 4.0, 4.0, 4.0, 1.0)transmap1 scale( models/mapobjects/skies/chumpskyclouds, 4.0, 4.0, 4.0, 1.0)transmap2 scale( models/mapobjects/skies/chumpskyclouds2, 4.0, 4.0, 4.0, 1.0)//fademap models/mapobjects/skies/skyclouds_maskcolor { 0.2500, 0.2500, 0.2500, 1.0000 }smatrix.w time * 0.015smatrix1.w time * 0.007wavefreq 0.100000waveamp 0.100000wavespread 0.000200surfaceRadiosityScale 0.75qer_editorimage "env/gskydome_px"}For the envmap it only looks like it only references the env/gskydome_px image. I can't find a reference matching it with the other images in the set eg. nx,ny,nz,py,pz, so I think that's just a direct reference to the .tga file and the skyboxmerge stageProgram (decl/renderProg/skyboxmerge) only refers to it as $envmap, so it might automatically grab the other 5 files (as long as they're named properly), then the transmaps are for the cloud layers.
textures/skies/sunset{stageProgram skyboxnoshadows 1envMap env/sunsets/sunsets_1/skywarp_forward.tga qer_editorImage textures/common/sky surfaceFlags surf_NoAreas}I tried adding one a while back and couldn't get it to work properly, the sky just turned out grey in game, but I only used one image, I think if you have all 6 named properly and point the envmap at the _px or _forward one the render programs will do the rest. In theory anyway lol
//Barrys Skybox Test 1 with scrolling cloud effectmaterial textures/skies/gskydome_baz1{nofragment 1surfaceFlags surf_NoAreasstageprogram skyboxmergenoshadows 1envmap linear env/barrysky/gskydome_pxskyScale { 1, 1, 1, 1.0 }transmap scale( models/mapobjects/skies/hlchumpskyclouds, 4.0, 4.0, 4.0, 1.0)transmap1 scale( models/mapobjects/skies/chumpskyclouds, 4.0, 4.0, 4.0, 1.0)transmap2 scale( models/mapobjects/skies/chumpskyclouds2, 4.0, 4.0, 4.0, 1.0)//fademap models/mapobjects/skies/skyclouds_maskcolor { 0.2500, 0.2500, 0.2500, 1.0000 }smatrix.w time * 0.015smatrix1.w time * 0.007wavefreq 0.100000waveamp 0.100000wavespread 0.000200surfaceRadiosityScale 0.75qer_editorimage "env/barrysky/gskydome_px"}//Barrys Skybox Test 2 without scrolling cloud effecttextures/skies/gskydome_baz2{stageProgram skyboxnoshadows 1envMap env/barrysky/gskydome_px qer_editorImage env/barrysky/gskydome_px surfaceFlags surf_NoAreas}Where material textures/skies/gskydome_baz1 has the scrolling light cloud/dust effect and textures/skies/gskydome_baz2 doesn't and both materials use the same six images for the skybox. I hope that helps