@ GPU_TEXTURE_USAGE_SHADER_WRITE
@ GPU_TEXTURE_USAGE_HOST_READ
T * read(eGPUDataFormat format, int miplvl=0)
bool ensure_3d(eGPUTextureFormat format, int3 extent, eGPUTextureUsage usage=GPU_TEXTURE_USAGE_GENERAL, const float *data=nullptr, int mip_len=1)