Investigate: 32 bit (4*8 bit) gradients

[mlavik1]

See discussion in #204

By switching to 8 bit components for gradients we could:

• Reduce CPU side memory usage to 1/4
• Reduce GPU memory usage to to 1/2
• Make rendering faster when using gradients (smaller texture fetches)

Implementation:

• Switch to Color32
• Use Texture3D.SetPixelData instead of Texture3D.SetPixels
• Switch to TextureFormat.RGBA32
• Add a setting for this?

Possible issues:

Precision will suffer. Investigate if this causes noticable issues. We might want to support both 8 bit unsigned int and half precision floating point format.

[SitronX]

Use Texture3D.SetPixelData instead of Texture3D.SetPixels

Just note, there is also Texture3D.SetPixels32 method exactly for this :)

[mlavik1]

Use Texture3D.SetPixelData instead of Texture3D.SetPixels

Just note, there is also Texture3D.SetPixels32 method exactly for this :)

Oh yes, you're right! Thank you :)