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Postby LK Crown » Fri Mar 29, 2019 12:23 am

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Subject title: Transition, very basic question, Cone in perspective

This is really basic, but how do I do the transition from seeing this cone from above (lower half) to seeing it from below (upper half) ?
This sketch looks like seeing it completely from above, which has to be wrong, because the horizon-line is in the middle.

cone.jpg

 

Postby svarn » Fri Mar 29, 2019 11:22 am

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Your cone just looks weird because it's really sloppy and the perspective points are super close. So you have a very distorted perspective. However in theory it's correct.
You won't see a clear indication whether it's seen from above or below like you have in case of a box (where you can or cannot see the top plane).
What you can do to show that is to add wrapping lines. What I did below is sloppy too, but it gets tricky with such a distorted perspective grid ^ ^"

Also when you're drawing cones, and you establish the center of your basis, make sure that center and the tip of the cone are directly connected via vertical line. Otherwise you just have a slanted cone which makes it even more difficult to judge.

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Postby LK Crown » Sat Mar 30, 2019 10:18 am

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Okay, thanks, that helped.

And if I have a box in perspective and I want to find exactly where the thirds are, how do I find it?
I know how to find the half and quarters, but what about thirds?

thirds.jpg

 

Postby LK Crown » Sat Mar 30, 2019 10:54 am

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Also, if I want a square-box, where all sides are equally long, but the flight-points are not 50/50 to each side, how do I know where the box ends here:

box.jpg

 

Postby svarn » Sat Mar 30, 2019 11:03 am

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Image

 

Postby svarn » Sat Mar 30, 2019 11:06 am

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As for the cube question. You don't know that. Or at least I don't think there is a simple way.
In architecture drawing class, they make you draw a ton of cubes specificly (from a reference of a physical cube), so that you can eyeball perfect cubes. It's important to develop that "space depth" awarness, there are probably ways to calculate them, but if I recall correctly it'd involve projections of top view etc. You'd spend a good hour on a very simple drawing, so nobody does it.

What you have so far, is already a flawed cube, because the side plane that you finished is a rectangle (needs to be taller)

 

Postby Audiazif » Sat Mar 30, 2019 3:23 pm

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Image
Here is another option on how to split up lines in perspective.


You take a line (blue) out from the front corner (parallel with the eye/horizon line). Then draw a line (far right, red) from the vanishing point through the back corner to the blue line, to establish the length of the line. Then you can divide the line however you want and draw lines to the VP from your divisions (red tick marks on blue line). Where the lines intersect what you are dividing is where the divisions are in perspective.

As for drawing a cube, there is a way to do it but it is a little more involved and complicated. It uses concepts that, judging from your previous posts, you are not using right now.
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Postby LK Crown » Mon Apr 01, 2019 2:36 pm

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Ah thanks both of you! Very helpful notes.

Audiazif wrote:As for drawing a cube, there is a way to do it but it is a little more involved and complicated. It uses concepts that, judging from your previous posts, you are not using right now.


Can you give a hint what the method is called or something? Maybe I can look it up and learn it anyways.

 

Postby Audiazif » Mon Apr 01, 2019 7:07 pm

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LK Crown wrote:Can you give a hint what the method is called or something?


For starters you need to understand what a "Station Point" (SP) is and how it is used. Then you need to know how to draw a perfect square in perspective, this involves using the "Diagonal Vanishing Point" which is based on the SP and VPs. And then you use "Measuring Points", based again on the relationship between SP and the VPS, to get the height of the cube.

I believe there are a few videos if you just search "how to draw a perfect cube in perspective". Sycra even has a video although he doesn't use many of the terms and it is not to detailed. Some vids are just regurgitating what Sycra did but some go into further detail.
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