Help on reducing DrawPrimitive calls

Why not put all 6 textures on a single texture map/atlas, and assign uv coordinates to the cube face triangles accordingly? Are you talking about 6 total textures, or 6 * number of cubes total textures?

Also, your large number of cubes problem sounds like a perfect situation for instancing.

Unfortunately these textures would be user provided content, so atlasing isn't possible unless I precompiled them, and I'm not sure I can justify that cost.

Is it possible to use multiple different textures on instanced objects?

You could use texture arrays so you could provide each face with an index to access the right texture. But as far as I know you will be limited by the maximum number of textures your graphics card can support at one time. I don't how many textures can be handled by todays cards, mine is supporting 8. So if you make sure not to use more than six at a time there should be no problem.

Thanks for your reply, quiSHADgho.

However, I can't find anything on google which suggests how to implement the method you mention.

Of course I can make an array of textures, but how do I feed them into DirectX?

Apologies if i'm being stupid or blind Thanks again!

Texture arrays were added in DX10/11, which allow you to create an "array texture", out of many individual 2D images -- this is a separate kind of texture to a regular 2D texture (not just an array of regular textures). When sampling from the "array texture", the [font=courier new,courier,monospace]z[/font] component of the tex-coord selects which 'slice' of the array to use.

On DX9, texture arrays aren't supported so atlassing is usually used instead. Even if your textures are dynamic, you can generate the atlas at runtime - e.g. just render each of your sub-textures into a larger texture at the appropriate locations.

In DX9 you can still use six single textures and a sampler array and access it with an index.

This is from one of my shaders:

Texture Layer1;
Texture Layer2;
Texture Layer3;
Texture Layer4;
sampler LayerSampler[4] = {
sampler_state { texture = <Layer1>; magfilter = Linear; minfilter = Linear; mipfilter = Point; AddressU = clamp; AddressV = clamp;},
sampler_state { texture = <Layer2>; magfilter = Linear; minfilter = Linear; mipfilter = Point; AddressU = clamp; AddressV = clamp;},
sampler_state { texture = <Layer3>; magfilter = Linear; minfilter = Linear; mipfilter = Point; AddressU = clamp; AddressV = clamp;},
sampler_state { texture = <Layer4>; magfilter = Linear; minfilter = Linear; mipfilter = Point; AddressU = clamp; AddressV = clamp;}};


I would second the recommendation to atlas your textures at runtime if texture arrays aren't available. It's not expensive to do once for each cube and you're just limited by the max texture resolution the API supports. (I commonly use texture atlasing for shadow mapping and those textures are updated each frame.)