Core77

[Sketchbook2]

Hey there,

For my current project I need to draw a bunch of irregularly shaped tubes that twist and bend in space. I'd like some help with depicting the turning shapes as well as marker technique for showing the form. Here are some quick pages that show what I'm talking about:

Thanks!

[KenoLeon]

Hey there:

Couple of things that might help you:

- Use an underlay or 2
- The turning shapes you are indicating are a result of the geometry & perspective, so in order to accurately represent them rather than guessing them you need to construct elliptical sections with a mayor and minor axis or midlines and connect them, all in perspective.
- Marker technique: consider the light source, material and how it reflects on both vertical and horizontal tubes and how it distorts on bends.

Let me show you a half assed 10 minute sketch to elaborate.

My barista tells me it should be a Juicer : )

tubs001.jpg (70.16 KiB) Viewed 6527 times

I did a shoddy job on the rendering part, so I would do a 3rd underlay or fix it in the computer, but the idea is that there is a light source and a type of material, in this case I was going for ceramic but came out mostly as nondescript (maybe metal) and the floor shadows are not well constructed, but the general idea is that there is a light source top right behind the object, where it touches the cylinder it is light ( using pastel blue pencil ) and where it's not it is darker ( using marker- copic B37), there is also a vertical light reflection in front that distorts ( compresses as it climbs up) and small shadows done with grey markers here and there, but darker on the sides.

And here is the underlay :

tubs002.jpg (72.15 KiB) Viewed 6527 times

The bottom left tube depicts the strategy, start with rectangular slices in perspective that encase elipses and join them with curves, what edges should be visible should become apparent at that point.

Hope this helps.

-K

[Sketchbook2]

Thanks for the response. I tried to take your advice and did a few practice underlays using a few different techniques. Some of them have good perspective, but I'm not sure if I'm connecting the ellipses right at the end...

[Sketchbook2]

some more pages.

[Sketchbook2]

and a few more

[KenoLeon]

I was looking at your sketches, before going into the rendering part, I think your ellipses and perspective could use some foundation work :

Consider 2 popular methods of drawing ellipses in ID:

tubs003.jpg (41.7 KiB) Viewed 6154 times

One is through the minor and mayor axis (the mayor axis points to the horizon and the minor axis bisects the ellipse in 2 equal parts if memory serves), and then eyeballing the ellipse on perspective, a vertical axis serves as a place to hang your ellipses, this is a very quick way of doing it, but lacks in precision and I usually use it when objects are floating in mid air, The Sketching series of books uses this a lot.

The other that I use (they are really the same if you think about it) , is starting with rectangles and a grid and extending them up down sideways etc with Scott Robertson black magic perspective tricks , whenever I need an ellipse or circle, I use the cross method from David chelsea, that is, divide a rectangle and on the diagonals mark a point roughly 2/3 rds from the center , connect this with the midlines and you have a pretty good circle or ellipse in perspective. Notice that no matter which method I use, I connect each intersection of line-ellipse point to it's brother or sister on the following ellipse, even the ones that are hidden by the object itself, keeps me honest.


These are just 2 methods, but what I've learned is that when I am guessing I loose the drawing, so I tend to rely on the second one more, which in turn generates some truly hairy underlays.

Edit: The work of Hakan Gürsu comes to mind for examples of more accurate underlays/inspiration: https://www.instagram.com/hakangursudr/

tubs004.jpg (41.63 KiB) Viewed 6154 times

So now that we got that out of the way and I ran out of paper, the corners or elbows of tubes are tricky because our brains suck at estimating the foreshortening of a curve in perspective, so we under/over estimate, consider the tightest elbow ; if seen from above it is a section of a circle, yet most people draw an almost 90 degree angle, to correctly display this type of elbows,use the 2/3rds ellipse trick on both sides of the bending tube and project this into the middle line.

tubs005.jpg (58.43 KiB) Viewed 6154 times

Notice btw that the line on the tight U bend you are after is first an artifact of geometry ( on the 3d model) , but is also accentuated by shading on the render.

Hope this helps you fine tune your underlays.

-K

[KenoLeon]

One more method for underlays:

tubs006.jpg (45.27 KiB) Viewed 6057 times

This is a mix or simplification of the ones mentioned before; draw a curve line in perspective and hang ellipses from it, then connect the vertical & horizontal cross sections to one another following the axis curve, this should define the geometry, if you need extra curves, like on the tight bends where it is hard to figure out whats happening, use a point in between the mayor & minor axis on the ellipse ( like on the second method mentioned above) and connect them to the same point on the ellipse above or below.

tubs007.jpg (36.5 KiB) Viewed 6057 times

The hard part is knowing which direction in perspective the ellipses are aligned to and imagining the POV of the scene beforehand, but practice and a few pages of warm ups does wonders, these are 3 quick examples with the original curves on the side.

tubs008.jpg (36.95 KiB) Viewed 6057 times

I might delve into twisting and shading if you (or anyone else ) finds it useful.

[ralphzoontjens]

So here's a more freestyle exercise.

As you can see I use the centerline and sometimes a square in perspective to help orient and proportion the ellipse.
The orientation perpendicular to the centerline and width of the ellipse are very important.
To get the 'ellipseness' of the ellipse right just requires lots of practice - let the movement come from the shoulder, hover the pen with smooth motions towards the ellipse you want to draw and when you have the movement put down the ellipse in a single stroke - that is the idea.
Also for all transitions clearly mark and draw a profile where they start and end - as if you were 3D modeling the shape in your mind.

Keep practicing, you are doing good work.
And be sparse with the highlights.

[Sketchbook2]

Hey all,

Sorry for the big delay in response. Finals got the best of me for the past few weeks. I've been practicing and I think I am starting to make progress. Here are some of my practice sheets. I threw in some practice doodles that look at prismacolor marker caps. A couple weeks ago I got my hands on a copy of Sketching: The Basics. Wow! Great book. I love the fast and loose approach - leaving in construction lines, using light grey marker underlays, not being afraid to change a drawing in progress, so many different material approaches.

[Sketchbook2]

second

[Sketchbook2]

third