Shading problem on a fish

Hi there ! I’m trying to make a fish in blender 2.79 (I can’t go further with my computer) but I’m running into some shading problems in Cycles… I have some very hard and weird shadows when I smooth it and I can’t seem to get rid of them.

I tried recalculating normals a bunch of times, checking auto smooth, checking for doubles and making the faces more planar but none of that seems to work for me.

I’m attaching a pic of the rendered result

Thanks in advance !

If that is a Cycles render, then is seems it’s the Shadow terminator artifact. Adjust the settings under Object Properties \ Shading. It is set to 0 by default, increasing its value fixes the problem.

If this is not a render but a screenshot, then turn on Auto Smooth under Properties Panel > Object Data Properties > Normals. There you turn on Auto Smooth, and play with the angle.

Thanks ! It was indeed the terminator artifact. However, as I’m stuck in 2.79 there was no setting, so the solution was simply to increase the size of the sun.

On another level, I’d like to have fins made from one plane with an alpha map so that I can have transparency. I tried extruding a single face from the model but I run into problems with the normals, especially on the edge that does the junction with the body. How would you go about it : extrude like this and maybe duplicate the face, or make the fins as a separate group of vertices ?