Before you delve into texture making, perhaps the texture you have is just not being rendered with sufficient precision?

If you're in P6, turn of texture filtering in render options. Verify that your Max Texture Size is not down-sampling the color map and bump map. If you have 4K textures, but your Max Texture Size is 1024 or something, you're blurring the image.

If you're in P7, turn it off in the material room, on each Image_Map node. Choose "None".

If you're still not satisfied, or that's already done, then go in you're render options, set the Min Shading Rate to .5 or even try .2 and Pixel Samples to 3.

Make sure you're not using any Post filtering.

Min Shading Rate will increase render times, but it may be worth it.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)