Optical Illusion or Not

The blue lines I've added to the photo look parallel, so it may just be an odd perspective.

Have your customer confirm that he wants the shape as shown in the lower figure.

Not at all!

It is a darned good optical illusion, but easy to figure out. Taking the top portion as being an arm that mounts back at the far end, one would expect it to be taller at that end. With the correct angle it makes the net look shorter in length and each end to be the same height overall instead.

There are 2 things that can be used for benchmarks- the height of the boat on the trailer behind (which is likely around 4'), and the difference in thickness of the posts at each end due to perspective, which will match up to the difference in height due to perspective. Given that I'd say this is indeed 5' at each end.

Good one though!

What you have to do is find the horizon line in the photo and draw lines from one point that aligns the bottom of the net to that horizon....then from the same point on the horizon to the top, and see if they line up....

All I have to say is 'good luck with that.'

the horizon is completely obscured, we han gen an idea of where it is from the street and houses, but is the street level? Are the houses square to the picture plane? The closer objects are of dubious help as well, a boat on a trailer is a perfect example of having lines and planes in every direction EXCEPT paralel to the horizon line.

I would strongly suggest asking the client for a second photo square to the net frame, to confirm the frame shape. Or simply send pack the sketch one of the other posters made with a note, "Just to be sure I'm seeing what I think I'm seeing, this is the way the frame is designed, yes?"

A picture with a ruler on it would help

Sure would.

OK.

It sure looked uneven to me though. they insist it was just the angle the picture was taken from.

they already confirmed the 12x5x12x5 Framing line and the other stuff. Production starts next week.

Thank you all for the back up. . . on another one of my Silly @$$ questions.

The shadow of the frame on the ground suggests that they are the same length, and the shadow of the light pole suggests that the sun is at the right angle ?

regards JD.

Just an optical illusion made worse by the fact that there is no frame of reference in the picture (no good horizontal or vertical) and it's taken at an angle.

It's like my pictures of bows. If I have a bow standing upright against a wall and I take a pic it always looks like the top limb is waaay too long. But if I kneel down to take the pic and get the camera level with the centre of the bow it looks ok.

Del

I prefer my references without frames. That way I can put them in my scrapbook.

It's a guess, but maybe the long triangle at the top is isosceles, the inner quadrilateral is a parallelogram, the outer quadrilateral is a trapezoid, and no lines mentioned so far are perpendicular.

YES. it is Illusion.

DHAYANANDHAN.S

Straightened photo, now decide

Some parts were measured with a regular ruler, and some with a fish ruler.

Do a google image search for "goal post" (might need to be soccer post where you are).

Lots of similar effects.

Not an illusion. Look at the angles of the top bracing spars. If the bottom spar was indeed level to the bottom spar the angle would be a 90 degree angle. The upper most spar is at 90 degrees with the frame. Have the client send you a square on photo against a plain background.

I am most sure indeed the frame is rectangular and the inside spar is lower on one side, (inside). The outside frame may indeed be 5x12x5, but the inside is not the same. The inside spar runs at an angle to the bottom pipe frame. Look again guys. Top is parallel, sides are parallel. Inside spar is angled upwards. Re-look carefully at angles not the back ground ref points or tilt.

Let us know when you physically see this frame,or have the frame owner send you a drawing of it.

Absolutely correct. The follow up question to the customer must be, "What is the height of the truss on the left side of the net beyond 5 feet?" We have to know that dimension to create the entire frame.

If the bottom spar was indeed level to the bottom spar My correction: the bottom spar level with the top spar. i.e it is a rectangle outside frame. The inside spar is angled upwards from the far side.

No illusion at all.

If line C is not parallel to the horizon, then you are not seeing the frame from a well centered frontal position, thus the perspective of even a perfect square, will make you see the top and bottom lines are NOT parallel, but at an angle which vertix points away from you.

Lets see if the Orig Poster provides us feedback as to the correct shape of the total frame. I am interested know too.

Lets put this in perspective. Oop, too late.

Customer still insists its just the angle and the camera. The sides of the Gate ( frame) are even at 5' (1.52 Meters).He said the old nets fit perfectly and they just need another set....same size.

It sure is one heck of an illusion.

Either, get ALL the dimensions specified, or get the physical sample to measure yourself. THEN you will be convinced!

If your making this net from the clients dimensions

get the down payment of 100% and put the responsibility on your clients shoulders.

Old customers. Good relations. However, i have an email stating that the measurements are 5' x 12' x 5 'x 12' ...same as the last nets i built them.

thank you all for contributing. I was sure it was a crooked frame.

that's a tough one, but you are looking after your customers

Always. its what keeps them buying from us rather than the outsourced nets that some others carry.

I think it's an optical illusion and a coincidence that the top bar appears to be parallel with the bottom. When we make drawings, we draw parallel elements parallel in the two dimensional drawing, whereas a camera lens will show nearer elements to be larger than those of equal length that are farther away.

I brought these guys down here to Louisiana and showed them two complete sets of frames for similar nets ( commercial grade ) that would work for their Research project.

I sent them home with pictures and CAD drawings laying it all out.

They did venture away from the original drawings one time and their venture cost them dearly. Now they tend to stay on the Tried and True path. It would surprise me IF they strayed again, but you just never know. I like to check out this stuff as much as I can.. . . makes for better relations with customers when they know I actually CARE if they get the right gear.

WELL.....whatever the case...the old nets worked fine built like they were. This just in.

They are ordering several sets of replacement nets and the scientist doing the ordering is an ex-officer from the US Army and has always been very precise with his measurements.

So , I guess we will say that it WAS an optical illusion.

THIS however, is not an optical illusion. they caught this the other night in a 10 or 15 minute push.

This is boat and those are the frames....with the older nets. Looks even side to me.

Thast was an excellent illusion. I was convinced the entire frame was rectangular with the inner spar slanting. Very good. It had me, for sure.

It is perspective distortion. The right side being closer to the camera seems longer than the left side which is further from the camera. A & B seem to be close to parallel and that is because the back of the camera was close to vertical. You may have seen a photo of a tall building that looks like it is falling backwards. That is because the camera was pointed up to fit it all in the frame and the vertical lines appear to converge as they get further away. It's like looking down the train tracks.

Get the original photo up on your screen and with a piece of card cover the triangular brace. Now it looks quite likely rectangular. Good illusion.

Jim

I honestly do not think they tried to do this as an illusion. It was just dumb luck that it came out that way. Scared the hell out of me that they would suddenly, with no warning or pre-thought, change a tried and true method after the last time ( several years ago) when they let someone with no experience...improve on the design, causing complete structural failure.

Thank you all again.

I would really like to see a square on photo of this frame. It is a really good optical illusion. A very cleverly cleverly taken accidental photograph. Impressed!

Can you update on the illusion. Rectangular main frame with an triangular top section? Curious for a good square on photo.

No photos forthcoming from client, but the frame is all squared up. The picture was indeed an optical illusion and a damn good one.

It is an illusion.

This one is similar shape, but placed properly, the top and bottom look parallel https://www.youtube.com/watch?v=tc_LqIaO2b8

If I were a woman, I'd ask where you started measuring from.

"Yeah baby, it just looks smaller because it's just an optical illusion. Trust me though. I measured it yesterday with a yardstick boiiyy!".