public void setDepthTarget(FrameBufferBufferTarget depthBuf){
        if (!depthBuf.getFormat().isDepthFormat())
            throw new IllegalArgumentException("Depth buffer format must be depth.");
        this.depthBuf = depthBuf;
        this.depthBuf.slot =  this.depthBuf.getFormat().isDepthStencilFormat() ?  SLOT_DEPTH_STENCIL : SLOT_DEPTH;
    }
Adds a texture to one of the color Buffers Array. It uses {@link TextureCubeMap} ordinal number for the
position in the color buffer ArrayList.

@param colorBuf texture to add to the color Buffer
@param face position to add to the color buffer
jme3-core/src/main/java/com/jme3/texture/FrameBuffer.java