Hi
The difference is in the VertexBuffer (IVertexBuilder) that you're using to render.
You can make faces only render on one side if you have back face culling turned on. Some of the render modes use back face culling, the others don't . Normal solid blocks, using RenderType.SOLID, have faces which are invisible from the back.
For example the difference between this
public static RenderType getEntitySolid(ResourceLocation p_228634_0_) {
RenderType.State lvt_1_1_ = RenderType.State.getBuilder().texture(new TextureState(p_228634_0_, false, false)).transparency(NO_TRANSPARENCY).diffuseLighting(DIFFUSE_LIGHTING_ENABLED).lightmap(LIGHTMAP_ENABLED).overlay(OVERLAY_ENABLED).build(true);
return makeType("entity_solid", DefaultVertexFormats.ENTITY, 7, 256, true, false, lvt_1_1_);
}
and this
public static RenderType func_230167_a_(ResourceLocation p_230167_0_, boolean p_230167_1_) {
RenderType.State lvt_2_1_ = RenderType.State.getBuilder().texture(new TextureState(p_230167_0_, false, false)).transparency(NO_TRANSPARENCY).diffuseLighting(DIFFUSE_LIGHTING_ENABLED).alpha(DEFAULT_ALPHA).cull(CULL_DISABLED).lightmap(LIGHTMAP_ENABLED).overlay(OVERLAY_ENABLED).build(p_230167_1_);
return makeType("entity_cutout_no_cull", DefaultVertexFormats.ENTITY, 7, 256, true, false, lvt_2_1_);
}
--> .cull(CULL_DISABLE)
If you're not familiar with backface culling it's probably worthwhile spending some time to learn a bit about OpenGL, this guide is not too bad to explain the basic concepts of rendering, worth a skim read for key concepts/keywords
https://www.glprogramming.com/red/
If you're worried about the back faces for efficiency reasons, I wouldn't bother. Quad rendering is extremely quick.
Cheers
TGG