Weapon Alpha

[Valo]

I've a bit of a conundrum. Perhaps you guys can help shed some light on it? 

See, I'm trying to change the way the map renders the sky background. Currently, it renders it by pasting a texture onto a cylinder thats wrapped around the room. This causes a few issues, namely that it warps the background and the 'polygons' of the cylinder become very noticeable depending on the room size.  The latter i know can be fixed by changing the number of steps variable in its argument, but it doesnt really fix the big warping issue. So I had a thunk. What if i use a similar method to how the hud is spawned and render the background as a sprite? Its doesnt have any details that would move or would need to rotate as you look around, so I'm wondering if making it a drawn sprite would work. Issue is is that I can't quite seem to get it to work...Everytime i try to render it using the same style as the hud, the room ceases to render in 3d. and i'm left with a sprite covering a big chunk of the view. 
For reference:
Cylinder type Mock up of what i'm trying to do(all textures are placeholders and/or tests of course)

The cylinder spawns via:

d3d_draw_cylinder(x-1024,y-1024,global.bg_z2,x+1024,y+1024,global.bg_z1-300,sprite_get_texture(global.bg_spr_tex,floor(bg_frame)),global.bg_hr,1,-1,16);

and how I THINK the bg would be rendered is:

d3d_set_projection_ortho(0,0,global.range_x,global.range_y,0)

draw_spritxt(spr_bg_tex1,image_index,0,0,image_xscale,image_yscale,image_angle,image_blend,image_alpha)

I'm not sure if thats enough context to help relay the problem, I can give more if needed. Does anyone maybe have an idea of whats gone wrong?