# Thread: Basics help - tilted plane

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## Basics help - tilted plane

Hi,

I'm learning how to draw using scott robertson's book but I'm a bit stuck on a chapter, copying tilted planes.
The copy techniques are clear BUT they never show how to draw the tilted plane to start with.

I tried outlining the examples to find my vanishing points but to no success.
Anyone here who can walk me through this?

It's a noob question I know but I want to get it right from the start.
You can take a look at my tries, it never feels right or correct.
Pictures from the book are included as well just to make it clear.

Thanks!!!

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3. Look closely at the first images. The coloured rectangles going from the corners of the tilted&rotated plane towards the mirror plane show you exactly where the tilted plane is located in space. With that info alone you should be able to redraw such a plane, regardless of where exactly you place your VPs.
If you're having problems understanding how the points are located in space and how to read that from those lins, I suggest you retrace some of your steps and jump back a chapter or so to get the basics straight. How to Draw is designed to be worked through chronologically, you need to have understood everything in one chapter before moving on.

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Hi and thanks for the quick answer!

The previous chapters all show how to draw regular planes in space using vantage points and suddenly the plane is tilted without further information. I'm having problems drawing the first black plane which will be copied further on.
The copying itself is not a problem but I need the "black" plane before I can start.
If all lines are parallel the drawing just doesn't fit.

So as I understand it I should focus on the mirror lines? Where the plane 'hangs' on the wall?
After all this obsessing I can't see the forest through the trees actually :p

5. I think the problem is that you don't understand what tilted& rotated means. I've redrawn the image in how to draw and put in a top view of the plane. Maybe this will make it clearer. All the corners of the plane have unique positions in space, there are no parallel lines (except in the mirror plane, which is of course parallel):

All the points have in common is the height coordinate (the two lower corners have the height 0, the upper corners have the height X). The other coordinates (lenght and depth) are different for every point. That's why the plane is tilted& rotated.

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I'll have another go at it knowing (seeing) it!
Thanks!

8. I've always found that the mjirror technique Robertson proposes in that chapter for tilted&rotated planes is overly complex btw., you can just use the rectangle multiplication technique to mirror all points separatedly and "connect the dots":

You end up having to draw more lines, but you don't have to deal with the additional complexity of the other mirroring technique.

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As it happens, I have the same problem and the solutions presented here do not clear it up unfortunately. The issue at hand is that the book never shows how to tilt a plane and place it relative to another in perspective in the first place. I am struggling as well setting it up. I don't know which lines actually converge and which are parallel (see page 36,top right image).

The mirroring part is a piece of cake, but before that, I need to have the tilted plane and the mirror plane to begin with.

Can someone please elaborate on how to do this?

Last edited by drawyks; July 31st, 2014 at 12:43 AM.

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As it happens, I have the same problem and the solutions presented here do not clear it up unfortunately. The issue at hand is that the book never shows how to tilt a plane and place it relative to another in perspective in the first place. I am struggling as well setting it up. I don't know which lines actually converge and which are parallel (see page 36,top right image).

The mirroring part is a piece of cake, but before that, I need to have the tilted plane and the mirror plane to begin with.

Can someone please elaborate on how to do this?

12. Originally Posted by drawyks
Can someone please elaborate on how to do this?
There is nothing more to elaborate on unfortunately. Look at my posts, I've broken it down as minutely as possible. My first post shows you a top-view of a tilted&rotated plane with the location of all the corners clearly shown. There is nothing more to show or explain about this. If you don't understand the illustration, you'll need to go backwards in "How to Draw" and get your basic understanding of 3D space up to speed.

13. I've built a tilted& rotated plane in sketchup. Maybe sseing this in 3D will help you to understand. I've included lines towards one axis so you see clearly how the points are located in 3D space:

http://poli.oppono.de/tilted&rotated.skp

14. I did some linear perspective vids that might help you out w/r/t inclined planes and rotated planes.

What I do with planes that tilt, is establish the form within a rectangle on the top and bottom, then connect them. If it's a ramp or something, you just add a horizon line and keep the vanishing points on the same verticals. If you're rotating, you just move the VP's over on the horizon line, keeping them the same distance apart.

Watch through the stuff in this playlist and see if that helps. Hit me up if you have more questions.

Cheers.

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Ok so (using the color of the dots for terminology)
the orange/brown TO purple line (top)
green TO lila (bottom)
move towards a shared vantage point I assume.

The lines towards the "wall" indicate how far that point is located from the wall (durr)
BUT
The descending lines
orange TO green
purple TO lila
are angled. How in all the known gods to the universe's name do you determine the angle in which they descend?

It's truly one of the most frustrating thought-prisons that I have ever gotten myself into.
Turn it into a cube and I draw it before I can think about how to.
Tilt and/or different offsets and I crash.

Everything is like: "vp here, vp there, connect, smile, party, etc..."
then suddenly: "draw a tilted plane."
:')

(it must feel like teaching mandarin chinese to ducks for the contributors, so thanks )

Often I draw a perfect tilted plane but it's not constructed, just drawn. Which does not quite work for a book like this.

16. Originally Posted by Spijker
Ok so (using the color of the dots for terminology)
the orange/brown TO purple line (top)
green TO lila (bottom)
move towards a shared vantage point I assume.
Yes.

The lines towards the "wall" indicate how far that point is located from the wall (durr)
Yes.

BUT
The descending lines
orange TO green
purple TO lila
are angled. How in all the known gods to the universe's name do you determine the angle in which they descend?
You don't, you just draw the points that are the corners of the plane and connect them. Ta-da.

You're over-thinking this.

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Hi Guys,
I joind to the conceptart.org forums, to seek help for exactly this topic! I'm happy I'm not the only one having trouble understanding "tilted plans".
I bought the "how to draw" book, and got stuck on this chapter, I just don't get it, what is a "tilted plan"? how to draw it?
I'm not reffering to the "rotated and tilted plans", I'm talking about the tilted plans. I just can't get it right, every time I draw it, it always looks wrong,
and I can't tell why.
Please, help me if you can.

18. @OrenHaberman, your construction actually looks fine. The reason the top line is shorter than the base line, is because the plane is rotated, the top line is deeper in space or closer to the vanishing point than the plane's base line. If the plane was not rotated or tilted the length of the top and base lines would be the same length in this example. I hope that helps, if not, ask away :-)

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Hi Jo,
Thank you so much for the reply.
Do you have the book "how to draw" by scott robertson? If so, take a look at page 36, top right.
There are tilted planes on page 36, and "rotated and tilted" planes on the next pages, it's very clear what makes a plane to appear
rotated, but it's not clear what makes a plane to look just tilted.

By defenition of the book, I used the method for mirroring just a "tilted plane", to mirror a rotated and tilted plane.
Should it still work? Im not sure. Because in the book there is a specific and different method for mirroring rotated planes.
It's confusing to explain this issue through text, if you have the book it'll be a lot easier to explain myself.

Here are two more pictures:
the first one, is a "Rotated and Tilted" plane, which looks correct, you get the feel that it's rotated and tilted twards you, and it looks like it's mirrored correctly.

The second one, is another attempt to mirror "just" a tilted plane, without a rotation, and looks wrong:

* the blue plane is the original, the red plane is the mirrored plane.

Last edited by OrenHaberman; January 3rd, 2015 at 05:49 PM.

20. You're welcome @OrenHaberman, let's see if I can help you here...

Luckily, I do have 'How to Draw'. As long as you correctly apply the rectangle multiplication/duplication technique to plot the corner points of the planes in the perspective space, it should work yes.

The reason your tilted in plane in your last post (#16) looks wrong, is because you made a mistake. When you transferred the top corner to the mirrored plane, you didn't project the plotted point back up to the correct top edge in perspective.

In paint over below, you used the top point you transferred as the bottom corner (red), instead of projecting it back up to the top edge (green):

However, you did actually do this correctly in your first post (#14). And your construction actually still looks fine from what I can tell just by judging with the eye:

21. @OrenHaberman - These perspective exercises can get a bit confusing, best is to keep your approach simple and focus on plotting one point at a time. I would suggest getting a 3D application and play around in 3D to familiarise yourself with how things look in perspective. Once you understand how it works it gets easier to imagine and visualise objects in perspective space.

Ask away if it still doesn't make sense :-)

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Hello againg Jo
Thank you again for your effort, and time to explain this to me. I appreciate it a lot!
Your 3d plane model and animation are great!
Actually I know 3D Studio Max, and I did try to understand this through playing around with simple planes in 3d's max, but unnfortunatly it didn't
work out for me.

I think that now it's more clear to me, I understand my mistake.
About the tilted plane, I just have to clear something for me, hope you don't mind

When drawing a tilted plane like in the page 36 top right, the two horizontal lines of the tilted plane goes to the right vanishing point, right?
But where do the two verticle lines of the plane goes? To a third vanishing point? Are they parallel?
About the mirror plane, do you think that it's going to another vanishing point somewhere on the horizon line, or is it constructed from two parallel lines?

I still don't understand what makes the top line of the mirrored plane to appear much shorter than it's base line, although my construction is correct.
Even in your animation (which was very cool and informative! ), it's clear that the top line of the mirrored plane, is not too short than it's base line.

Why Scott Robertson and Thomas Bertling made a video on how to draw straight simple lines, but did not make a video about this? It's so frustrating

Anyway, thank you again so much for your help!

23. No problem Oren, I very recently did the same exercises and I'm still working through the book, so this is kind of a test to see if I actually learned anything. :-)

Your first question is basically the same as Spijker's question (the original poster), finding that third vanishing point in order to be able to construct the tilted and rotated plane.

The main problem here, is that the purpose of the exercises on pages 36-38 are about Mirroring Tilted and Rotated Tilting Planes, and not about actually being able to construct these planes at this point in the book.

All you need to be concerned about at this stage, as Benedikt pointed out, is the points of the planes and mirroring them using the rectangle multiplication/duplication technique. As for finding these points in space, refer to Benedikt's posts earlier in this thread. Or just trace them straight out of the book and do the mirroring exercise.

What is also implicated is that when you reach this point in the book, you should at least be able to understand how an object (or a plane of an object) could deviate, like tilting and rotating, from the basic parameters created by the Point of View in a scene.

Like Benedikt also said (#2, #9), if you have difficulty understanding how an object can tilt and rotate on an axis different from those set by the Point of View of the scene, go back to page 22 and make sure you understand the basic concepts explained from there on. Do not get ahead of yourself, it will only cause you confusion later on.

That being said...

"When drawing a tilted plane like in the page 36 top right, the two horizontal lines of the tilted plane goes to the right vanishing point, right?"

Yes.

"But where do the two verticle lines of the plane goes? To a third vanishing point? Are they parallel?"

Yes. They are parallel to each other, but not parallel to the horizontal or verticals as set by the Point of View of this scene, so they will eventually converge at a Third Vanishing Point, or an Auxiliary Vanishing Point (Sneak a peek at page 108, top right).

This third vanishing point, the Auxiliary Vanishing Point, might not be on the scene's horizon line, since the plane might not be parallel to the horizontal or verticals as established by the Point of View of that scene.

To use your drawing as an example for Tilted Planes:

Because the planes' top and bottom edges are parallel to the ground plane (the plane is just tilted, not rotated), it will still share a common horizontal vanishing value with the scene:

And if the plane was to be tilted and rotated, meaning no parallel or perpendicular edges to the scene, the plane's auxiliary vanishing points deviates from those set by the scene's Point of View:

Basically, this illustrates the point that a scene can have an infinite number of vanishing points depending on where and how the objects are orientated within that scene.

But don't worry! This might look almost impossible to accurately draw, but the book will help you understand this better as you continue, and it provides easier methods to construct tilted and rotated planes. Keep it simple and focus on what's at hand, mirroring those points using the rectangle multiplication/duplication technique.

"I still don't understand what makes the top line of the mirrored plane to appear much shorter than it's base line, although my construction is correct."

That's just it, in perspective view things appear smaller the further away they get from you. In this example, all the cubes are technically the same size in an orthographic view, but when viewed in perspective they appear to get smaller the closer they get to the vanishing point or, in other words, the further away they are from you.

To get back to your drawing, the top line appears shorter because it is further away from you in perspective space, which means it converges to the vanishing point.

I hope you can make some sense of all this, I've never had to explain this to someone else.
If it gets frustrating it means you are learning something, that's why we're here, right? Hit me up if you need more explaining.

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Jo, thank you so much.
This subject is so much clear to me now, thanks to you!
I'm really amazed with your patient and will, to explain this to me, I appreciate your help!
I will keep on practicing tilted/rotated plans till it will feel natural to me and then after a long time not progressing with the book, I'm planing
to keep on reading, at last
Thanks man!

25. Sure thing Oren, I'm glad we could clear it out for you
Get a sketchbook going here on CA if you want, would love to see your work.
Feel free to hit me up if you need more help. Rock it!

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