Ghost

First off; Basic idea on how the light refracts inside a solid transparent object:

Wether it is acrylic, glass, water or crystal, the way light pass through more or less should behave the same as long as it is solid and not hollow inside. Pay attention to how the darkest parts of the stone goes along the inner edges, leaving a ”mid tone” sort of in the center. However, this might vary depending on the light setting. But it is a generally good rule-of-thumb to follow if you’re drawing something not based on a photo. Another thing to pay attention to here is how the placement of the highlight will lit up the inside of the gem in a parallel line. It also shows through on the cast shadow.

Light refraction on a cube:

I have already made two posts on this, so definitely go through them:

CUBE BREAKDOWN POST HERE

But a rough summary from those two links would be: Every side/facet of a gem or a cube etc refracts the light individually and not as one entity (that would make it look hollow and not solid). Think of it like how each piece in a broken mirror individually reflect your face back to you. Like a weird patchwork!

Putting this into practice:

For this tutorial I’m going to be nice to myself and not try to draw perfectly accurate gemstones. Instead I’m gonna draw them with a more ”natural” looking set of facets. Which actually isnt as common in real world as video games makes us think. Some crystals have geometric shapes naturally, but a lot of other stones are not as fancy. Anyway, im taking artistic liberty on these example stones because the technique I’m going to use will work for these just fine.

So, in clip studio paint, I first draw the stones on a vector layer. I give them facets for the front side. Then I duplicate the layer, remove the front facets and replace them with the facets on the back of the stone. The third image here shows both layers visible on top of each other. I now put these into a layer folder and mark the folder as ”reference”.

Now, on a layer below the lineart folder, fill with your base tone. Then make a layer on top (if you can clip it to the base tone, do that), this layer is where you decide where the highlight will be placed. In some cases the highlight is only lighting up one single facet - it really depends on the design of the stone. You can also blend and soften the highlight here if it looks good for you, just make sure not every facet is highlighted. The highlight layer should be on top of all the other layers clipped to the base tone layer.

Now it is time for the juicy juicy stuff! Turn on both lineart layers so they’re both visible. I hid the hilight layer here because it was in the way, but might not be needed in your case. Make a layer clipped to the base tone and paint in the darkest tone. This is where anti-overflow helps me out, because when i run my brush over all these crossed lines it will make the stroke pop in and out for each facet. If you dont use CSP, this is where you can use the lasso tool and select every second facet. It will take a bit more time but it should work similarly.

After the darkest tones I then make a layer for the inside light that the highlight has lit up. Here i keep it inside the darkest tone but this might vary depending on the light setting. If it looks good to me, then that’s what i stick to.

The way I approach rendering the facets here is like the grid in the example images above, every shade and tone appear more or less in each facet but the amount is relative to their position. So a gradient wouldnt have a smooth transition; it would be slightly scewed in each square on this example grid. Essentially like how some bathroom window glass panes look like.

Now it’s time to hide the lineart layer folder and check if the gemstones look decent to you. If not, then you can look up some reference photos and analyze where the values group together the most; be careful not to focus too much on the photos 500 million sparkles. Squint your eyes or blur the reference and try to see how the overall values behae.

I, personally, am satisfied with these rocks so I slap on a gradient map (you can manually color in them too if that’s your thing) and call it a day. The lit up inside of a gemstone tend to have a brighter and more saturated color than the mid tone.

Other Examples with this technique:

If you look up ”gemstone types” you can often find images displaying various facet types from more than just front view. These can serve as useful base templates for practicing this rendering technique. The backside of a gemstone is called the “pavillion” and is really useful to have at hand when it comes to painting the inner refractions. You can probably also use 3D models and convert the wireframe into lineart. But that is slightly out of my pool of knowledge.

Applying this knowledge without using a base lineart layer is of course possible. In this painting I followed a simplified summary of how the facets sparkle: Keep the highlight shape to match the front facet design, and all the inner refractions should be more scattered and split up but face a direction towards the center of the gem. Now don’t you think this sort of makes the gems look like eyes? That’s right! You can, and absolutely should, apply this on eyes to create the most sparkly anime eyes ever.