A tilted cube/prism in perspective? (not parallel to ground)

[Raymond Luk]

Sorry, I know I keep making all these perspective threads, but my cheapo 20 buck perspective book ain't covering it, and neither is my intro to imaging systems class (where they teach beginner fundamental perspective)

So I was thinking, to make a tilted object, I would need two vanishing points that aren't along the horizon (since the x/z or y/z axes are sloped like a ramp)
But then I remembered that in 3 point perspective... the third point is used to indicate the z axis, which is perpendicular to the ground... (like buildings...)
So then, how do I make it tilt certain angles...

Other than that, assuming I'm using two other points to create the tilt, would I draw the points along a line going...

[JFierce]

Well I looked at your SB. You've made a couple threads on perspective and such but.... well..... ... I don't see any actual practice on perspective in said sketchbook. Lots of figure work and such but not any actual geometric practice. Reading and knowing the basic rules and all is nice. But you still have to practice to get a grasp of things.

Getting something to tilt in space isn't that hard. It's a lot easier to observe the phenomena in real life than trying to figure it out on paper. Then you just have to practice. Internalize it. I remember I used to sketch random cubes a lot even if it was just quick stuff without carefully measuring every angle but simply shifting the general angle around in my head which got better with practice. From life and imagination


Was going to do a quick doodle but it's late and I remember uploading a quick sketch of cubes I did ages ago I uploaded here anyways. (Though this doesn't include any strong 3rd point or anything)




Just do simple geometric sketches, either practice from your head like the above or literally just take an object in front of you and shift around that. Put it on a stool and draw it from below, change the distance. Put it on the ground draw it above. Put it on an angle itself. Go outside your house or building and look up, or if you can like in the city go above the building and look down, there you go. That's your peek at 3 point perspective. Work with simple geometric shapes and then work up to more complicated things.




Practice maaaan, practice..... all these complex grids feel like your making things more complicated than they need to be. Especially since your not going to use them for more complicated or organic objects and often your VP's are going to be waaaaaaaay off the page which your going to have to learn to probably eyeball a lot of it. Which all comes from practice lol.

[Raymond Luk]

Ha ha, I actually don't have any formal studies either Q_Q Too much procrastination and homework .0.
I'm all for eyeballing it, but it's just that this is going to have to be really perspectively accurate since it'll be used as part of my portfolio for art school :0

Umm as for practicing with geometric shapes, I'm actually doing all the perspective understructure now, which is why I wanna know how to tilt it After I finish this, there won't be anything as perspectively complicated in terms of homework, so i'll have some time doing actual studies, I reckon. So far i've drawn a ton of circles, some spheres, and the basic cubes and stuff :s

Bleeh, I'm like the mathematical types who like to know how everything works .0.
Hmm, do you think we can rotate an object using a cylinder as an overstructure? ._.

[Care]

god i tried to explain but realised i cant sorry. anyway in 3pt, of the vertical lines, 1 pt will have to goto the 3rd vanishing point, the other point is the one you can move to show tilt

[AndreM]

Hi Raymond,

That's an interesting topic!
I think the reason behind the lack of information on this topic in your book is that it requires some math to rotate objects.
Even though a rotation around the up/down (lets call it the Z-axis - it differs from field to field) axis is simple to illustrate by moving the vanishing points left and right, calculating the distance is a bit harder as you have to move the vanishing points along the horizon - and they are rarely moved equal distances (since the Y and X axis have to be perpendicular to each other)


Image taken from http://www.math.utah.edu/~treiberg/P...t/Perspect.htm - This might answer your questions, but as JFierce said, you are probably better off practicing drawing them. Found this by googling "calculating perspective view".

That said, your example lacks information. What are the vanishing points (initial and rotated?), what object is being rotated - it looks like a 2d tile which is a bad example when dealing with perspective? How is it being rotated? What point are you rotating around?
If it's meant as a study at least it should have some notes

[Raymond Luk]

Heh heh it's alright care, I sorta get what you mean, like having a pivot point :0

And thanks for the response andre! :0 The circle thing reminds me of what someone told me :s That if you can draw a perfect square (in a circle) you can rotate anything
Hmmss, My object is uhh rotating around it's own mid point actually :-0 I guess the circle would enclose the object and it'll have to be measured out then .0. Now how do they do character rotations ._.

I took some pictures and realized I could toss it into photoshop and try to figure out the perspective, needless to say, I got stuck again @_@

Here's the object in question :0 I'm trying to draw the tilted handle


So I guess I found that the tilted part goes left right instead of up down :0


But i'm trying to fit the tilted part on a rectangular prism constructed in normal two point perspective....(And the points don't match up) I wonder if I have to construct the circle with the tilted vanishing points....? ._. (But it'll go into the ground then @_@) I'm lost... again ;0;

[[email protected]]

The easiest way to do this, is to rotate your paper and draw a cube in proper perspective (1, 2, 3, 4 point). It is really like putting your camera at an angle: nothing in the world really changes, but the horizon is no longer horizontal. The proper way to do this, is to learn how to construct your horizon and vanishing points, as AndreM shows you for 2-point perspective. The construction for 3-point perspective is more complex, you may never use it, but it is good to understand the idea...

[Care]

right i got it! the prob ur having isnt because of perspective, but because of ur understanding of the object itself. looking at the mug, the handle is on the bottom plane. That is the mug is resting on a corner, and the bottom plane (with the handle attached) is angled towards the floor. what your trying to do in ur pic is draw the hand on the corner, which isnt the case with the object itself.

1.) the handle is on the bottom of the object,
2.) you could maybe try both drawing the object as a cylinder and a box so u can understand the planes

I hope this helps, dont worry perspective is hell at first. gl stay frosty

[creeptool]

this looks cool..Perspective by Gary Meyer http://www.thegnomonworkshop.com/store/product/1014/ IF ANYONE OWNS THE VIDEOS HOW OR THE VIDEOS OR THEY ANY GOOD?

[JFierce]

The problem I see is the cylinder your sketching isn't the perspective of the picture.... or the perspective of the other rectangle sketch. They're all different based on the pictures your showing. Attaching a rectangle to that cylinder would actually be very easy once you establish the perspective of the cylinder itself.



Pardon the crude minute sketch. Not accurate but just trying to illustrate that they align exactly then it's just an issue of getting what angle it sticks out from the cylinder.


Still feels like your over thinking and diagramming it lol
Looks to me you can attach that handle just by drawing the same exact line down the side as the cylinder but out a bit more from the cylinder/cup, then use the arc of the cylinder with that to get the rest rather easy. Looks like you were even doing that but doubting yourself.

[AndreM]

Also pay attention to your vanishing points, I think the cyan coloured vanishing point is off (it sort of fades into the distance as it comes closer to the viewer it seems, with that vanishing point)

It helps to think of the image and what points will be closest to you / what points fade into the distance, and then use that to establish your vanishing points.

I played around with the cylinder for a few hours, turned into a study but ran out of time for today

[Raymond Luk]

I appreciate you guys taking the time to respond :0 Rotating the paper I never would have thought of :s

Andre! Especially, AWESOME study! It looks mighty neat and cool! Motivates me to do some perspective studies of my own. xD
Ahh i didn't think all 3 points would be on the same horizon :0Bleeh back to the basics for me @_@

[AndreM]

Hey Raymond,
I think you misunderstood me (or I am misunderstanding you so this is just to clarify!), you will never have 3 vanishing points on the same horizon for the same object. The vanishing points follow the dimensions, so you will have one vanishing point in each x, y, z direction, perpendicular to each other, for each object.

The easy thing with perspective on buildings/cityscapes is that they usually have the same orientation, so they follow the same perspective lines - But dont let that fool you

Also on perspective (but not relevant to the cylinder):
When one of these x, y, z directions of an object/plane are parallel to the viewing plane, you loose a vanishing point.
(As an example, try staring at the center of your screen, when you do that, you get a 1 point perspective because only the depth of the screen can be drawn with a vanishing point, the other axis (x & y) are parallel to your viewing plane (same as perpendicular to your view direction)).

In that way, 2 point perspective happens when only one of the axis are parallel to the viewing plane.


The "3rd" VP on the horizon, the cyan one, is actually the 2nd VP of the box/handle and is not directly related to the cylinder - and I think I placed it a bit off, it probably follows a different horizon because its up/down axis (which I did not paint in, should have done!) is different than that of the cylinder.

I think a good exercise would be to take a step back to the basics and draw perspective / VP lines on buildings and photographs (but start simple, that cylinder over complicates things)
Also, maybe you can try to take pictures of a box where you force the vanishing points - Determine what vanishing points / perspective type you want, and then take your picture so it matches the proposed vanishing points. Should be easy to get 1, 2 and 3 point perspective figured out that way - and that would probably be the best way to study what happens to the vanishing points when an object is turned, too!

Sorry for the long post

[Raymond Luk]

Thanks for the clarification, I appreciate the long post, it's very detailed You really summed it all up for me xD
These vanishing points and different perspectives do a chunk to confuse me @_@

And great suggestion! :0 I'll definitely be starting that real soon, ain't nothing like learning from the real world xD