>>25176
Time for real crit. First starting with the requested point, the hard part about making the body seem 3D. I will use grayscale photos both because these match your Arachne's skin more closely and because it makes it easy to focus on shade value. The first thing is that
with poor light, reality can look flat (first photo), but as an artist you
choose the composition! From experience, I know a sidelight gives good shadows that accentuate the fine details of anatomy, so I chose the sun to be more to our left (her right). This let me put the second reference photo to good use on her abs, arms, and roughly on the contour of her breasts. I applied this to the cloth folds on her shirt freehand, but done quickly and without accounting for her arms beyond the hands. That's because if all gems glow with internal light, they'd brighten anything near them and totally change the lighting, whereas if they only reflect, they'll be fairly dark and the arms will case additional shadow on the shirt and ribcage. The best way to see how low the arm shadow would go would be to try the pose in front of a mirror, I'd bet you'd get a diffuse shadow even on the upper stomach.
Moving on to hair, and the gems which share the ability to do bright reflection, I only did a small portion of what would be needed, in a few different styles. Her hair on the upper left gets a bright single shadow that dips with each clump of hair in her bangs, making them seem more 3D. This is the "90s anime" style except done very quickly and poorly, whereas in some of those drawings I'd wager they spent an hour on just the hair, like this Eva pic by Yoshiyuki Sadamoto. You can see that he uses sharp planes on the Eva itself, but chooses to fine-detail the hair by breaking it into 3-4 sections like the Z-Ton drawing, then dividing those into 3-4 clumps each, then drawing a few hair strands individually. He also cheats on the lighting for Rei: it would seem to be upper-right by her face and plugsuit, but that should also light the center-left portion of her hair instead of the far left. He gets away with it because locally, it looks correct, with the center-right hair partition being highlighted as if light was coming from the left. I call this out because it shows how you have to learn the rules to get away with breaking them. Like perspective and shadow make you think a flat drawing is 3D, ensuring an area looks locally correct will be fine so long as it's not a major focus of the drawing. For the gems here I give two examples: the upper-center on her stomach is the "typical fantasy gem", a polished circle or rounded rectangle. The upper-right stomach gem is directly referenced from the attached garnet, and so feels much more real, but out of place unless you gave similar treatment to every gem.
All of the stuff I've done here is just a set of hints. You could make it better by spending more time on blending and applying the techniques everywhere, and you could choose other solutions like going for full Sadamoto hair rather than my "Eva as animated" hair, which has far less detail in the highlights due to cost of animation.
Last, to go over critiques not explicitly asked for, and probably not worth adding here, there are several things to think about. My stance here is that if you just keep redoing one drawing while learning it can get frustrating, so even if she's your literal dream girl you might be best served doing other pieces and returning in a few months for a complete redraw.
>The front spider-thorax area feels flat like the body did and for the same reasons, it would need to change shades on the sides/bottom to indicate a more 3D form. Darkening the bottom quarter and right side would help as a quick test (50% opacity dark blue/black in its own layer on top)
>It would be more striking if the spider body cast shadows on the ground coming out from the legs. In reality this shows poorly in thick grass, but if the grass is that thick, draw long strands that obscure her feet so at least it's clear
>On the other hand you use same-length or longer grass strands in the distance and it hurts the sense of depth, though luckily not too much since they're not high-contrast. The two solutions are either to let them go above the horizon, in which case it seems like a hill that crests a few meters beyond the egg, or if as I suspect it's a long plain, then to halve the height of the grass strands for every clump you move up, reverting to clumps and then whole features before you get to the horizon. I'll attach the bootcamp on how planes for bodies and landscapes can be similar in a followup
>Color-wise, the very green grass is perhaps too strong a contrast with the red glow. Shifting it to red in the current glow radius, orange (as now) in the rest, and blue-with-hint-of-green shadows would unify you around a red and purple palette that's more striking. If nothing else, as an experiment think how you'd color this if the scene was on the night of a full moon instead of during the day
>Simply because the rest of the Arachne is high-detail, I would add more definition to her neck: a darker shadow from her chin, and maybe a shade/highlight for the neck muscles that make a V-shape connecting to the collarbone (the sternocleidomastoids if you want to look up a muscle diagram)
And remember, all of this is just fuel to do better in the future. I still often find flaws in my drawings, and either have to correct the sketches, or if I'm further along than that usually just finish and resolve to do better next time.