form intersections are super difficult....

2:36 AM, Wednesday July 15th 2020

just practicing form intersections again. i finished lesson 2 already so im practicing digitally for a bit but i still cant figure out form intersections for the life of me... after you put down two forms i have no clue what to do next or what lines to put down? any help would be appriciated greatly! (I seriously dont know how to dont them well at all and its getting frustrating for me a bit haha....) (my attempt at a form intersection after a while)

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10:09 AM, Wednesday July 15th 2020

I tend to choose one line that goes into the plane of the other object and darken that. You kind of have to imagine it in 3d space and follow it until it looks like it hits it. Once you establish one line it becomes easier to see what is going on but you have to make that choice first. It establishes which form is in front of the other.

10:33 AM, Wednesday July 15th 2020

sorry i still dont really understand how you "choose one line" where do you start to draw the line?

2:58 PM, Wednesday July 15th 2020
edited at 5:10 PM, Jul 15th 2020

I had to experiment a lot before getting it ( I think ). It's easier to try a lot of examples and see what looks right.

Break it down to the simplest example.

Draw a plane in space like in the earlier exercise. Draw a line that goes over the the top of it. Now start inking from one end of the line until it looks like it has reached the the plane. Stop there. That is a basic step of the exercise.

I think it is something that you need to keep trying, evaluating, and eventually something clicks. Rewatch the example videos too.

PS I now remember that I created a couple of A4 sheets of shapes. I then printed out several copies of each. I practiced on these until I managed to get the hang of it. You really have to use your brain to visualise.

edited at 5:10 PM, Jul 15th 2020
12:46 PM, Thursday July 16th 2020
edited at 1:09 PM, Jul 16th 2020

I had a go at the first one. I would advise you to keep it simple to start with, this one is very complicated.

And if you choose to swap the boxes around.

This is why the first line you decide on fixes which way the objects intersect.

edited at 1:09 PM, Jul 16th 2020
1:58 AM, Thursday July 16th 2020

hello thanks for the advice it helped me a lot!

i have some examples of me practicing. im not sure if its right but i attempted haha....

for #1 in the example, i have no idea where to start and end the line?

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3:03 PM, Wednesday July 15th 2020


I see your intersection on the top is changing directions 3 times, but it should be a strait line. The intersections change direction only when they touch an edge.

To start an intersection, you can choose a place where an edge of cube A enters a face of cube B. Then, you can trace a line parallel to the face of cube B until it touches an edge. Then you find the face you want to continue your intersections on and continue your line parallel to that face.

Here, take a look at my form intersections and isolate to cubes to study them. They are by no way perfect but Uncomfortable said I had a good start :

Have fun!

1:53 AM, Thursday July 16th 2020

hey there thanks so much for helping me out!

i did notice my lines change direction too much, so i tried to practice that (no clue if it is correct but)

what counts as an edge ? for example im having a lot of trouble on #1 in the image example. if i draw a line where do i stop the line?

2:40 AM, Thursday July 16th 2020

Hi there, you're welcome!

Okay open this image :

First, good job for the number 2. Even if those lines touched others, you did well not changing their directions because those lines were delimiting other faces.

For the number 3, you missed an edge. Your intersection touched an edge of the box on the right, which was supposed the make the intersection deviate. There, I put 2 examples of what you could have done. They seem similar because the angle vary only slightly but in one example, the line I point is parallel to the edges of the box on the right and in the other example, the edge of the other box.

For the number 1, I broke my rule of the intersections needing to be parallel. I told you that rule to make things easier at first, but as you progress start breaking it. Honestly, you can redo that same example in many different ways. If the box on the right was totally behind the one on the left, there would have been no intersections. if the one on the left was slightly behind the one on the right, the intersections would have been totally different. It is about imagining which box is over which box, then trying to see how the faces would touch each other. Try different intersections with the same example :

  1. The left box really in front of the right one, but still touching.

  2. The right box really in front of the left one, but still touching.

  3. Left box slightly in front of the right one.

  4. The right box slightly in front of the left one.

It will be hard but since you're attacking your weakness, I am sure it will do wonders to your capacity of visualizing 3D space!

Keep up the good work!

4:56 PM, Thursday July 16th 2020
edited at 4:57 PM, Jul 16th 2020


i tried to practice again do you think these look correct?

(sorry for the blurry pic it seems my file got messed up a bit but hopefully u can see)

edited at 4:57 PM, Jul 16th 2020
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