[amnesia]

Hope my cubes aren't too late.




------------------
,.-="`AmnesiA`"=-.,

[Sumaleth]

eetu: Yes, unfortunately we didn't really get a definitive description of the environment in order to be able to really understand what should be going on. But from Craigs comments it seemed that a surface which is facing the light source, even slightly, along with the effects of bounce light will show that surface to be more white than you'd typically expect it to be (Spooge mentioned this on my first image). Maybe Fred can explain that some more .

AliasMoze: It may be that the cube on the left is a full cube but it doesn't have the appearance of being so . This is probably largely due to the perspective space of the scene being established by the cube on the right, and if you were to mentally rotate that one around until it was at the same rotational angle as the left cube it doesn't appear that it would look the same - it looks like it would have more depth.

Perhaps this is just an illusion, which is certainly possible. Did you do it as a top-down projection (likely to be accurate) or by using two sets of vanishing points (we still haven't really nailed a totally satisfying explanation of how two sets of VP's work together). It would be interesting to see your construction lines for the scene.

Oh, I spotted another problem that I missed first time; the cast shadow from the left cube on the right cube is too dark, it doesn't match the value range previously established as "shadow values on vertical surfaces".

Cheers,
Sumaleth

[AliasMoze]

Sumaleth,
Yeah, I drafted it in PS from the top view. It's entirely possible it's off from just sloppiness in the construction. It's hard to knock something that's drafted correctly, but it'll never be 100% (line thickness, etc.) For my next one I'm going to use Illustrator to draw the shapes. However, rotated cubes in perpective sometimes just look weird. Poor construction and lighting seems to help in the crappiness.

Yeah my values are not perfect yet; I'll keep painting these things until I get it right. But I have to say these things are teaching me allot about painting in general. Everything else seems much easier with every cube I paint. Kudos to Fred.

BTW, if you look at the images in the original post by Fred, the shadow cast on the cube at the top right looks pretty darn dark. I tend to paint the main shapes, then the cast shadow relative to the object it's cast onto. Hmm...we'll figure it out.

Anyway, ahem, I wish Fred could critique my cubes. Cough, cough.

[This message has been edited by AliasMoze (edited May 30, 2000).]

[Fred Flick Stone]

Thank you Sumaleth for helping a bit. I haven't read what you wrote yet, you went through quite a bit of trouble there, but I am sure there was quite a bit of helpful info there.

My house hunting situation is getting a bit dire, as I have not yet found a place, and the time is growing short.

I just spent the last hour critiquing images that spooge already critiqued, I feel like an ass. All that work for well nothing now. But after I read his crits, I said the same thing, so I know I am on the right track with getting harsher, and buckling down with you guys, so yall can learn the right stuff. I have to get back to the work load now, but I promise, tomorrow I will critique the right images.

This might be stretching it for most of you, but since I want to learn to do this stuff correctly, I went out and bought at a craft store, stryrofoam cubes, spheres, cones and cylinders. The only problem with them is at the edges of the objects, they are too ttransparent, because of their brittle surface. Beyond that, they work great for lighting, and seeing what happens with all that reflective light. You guys might want to consider this, instead of inventing these things out of your head.

Oh yeah, keep up the great efforts. You will be addressed, I just need more time...have a nice day...

Fred

[dines]

Sumaleth, thanks for your help (i'll try to redo the whole stuff)

btw i had an idea for the tutorial process,
not how to do it but concerning the organisation of the forum,

i don't know how many people have fast line (i have one at work)
but on a 33.6 modem the page appear too slow and even stop to load...

maybe is it possible to create a new section in the forum (for the moment there is 2 section art & musing ...)

My idea was to create one big thread in text mode only, with all the ideas, the critics

and for the graphic posts
each guy doing something can create one thread with his work

i don't know if what i writed was clear, i know i made a lot of grammatical mistakes,
(ok being french is not an excuse)

dines http://www.nexen.net/koubis

[synj]

-synj www.synj.net

[AliasMoze]

Fred, I made some of my own cubes out of bristol board. They're pretty matte, no soft edges. They're good to look at for me, especially at night with nothing but artificial light. Anyway, we'll keep banging away.

[Zaphod]

It has been a long time since i posted here last time. Hello again (if someone happens to remembers me )
Anyway here's my cube (I made an arrow to clarify things, just in case ):



------------------
/Zaphod
http://www.designmodule.com.bi

[This message has been edited by Zaphod (edited May 30, 2000).]

[Sumaleth]

Dines: if you turn off image loading in your browser it should only load the text and then you can selectively view images.

Hope that helps a bit.

Sumaleth.

[Dizzogg]

Here is my second try.....What'd you think?? Still needs a lil work eh? Im thinking that
actually lighting some actual cubes would help with this lesson. Man and you would think I never went to school 2 yrs. :P



Now that I look at it, I notice that my lighting is a bit weird. Im thinking that the left cube's far left face should be darker and the right face a lil lighter since the light source is coming from a lil above the left cube.....Im learning....Still a ways to go...


[This message has been edited by Dizzogg (edited May 31, 2000).]

[iska]

Sumaleth, thanks for your comments, I gave it a new shot and heres the result.. I guess I ended up blurring too much of the ends of the shadows or something. Well.

[Joachim]

Thx alot Suma
I really appreciates your comments

Also, I agree on everything you said...Except one, The cone shadow, I don't think it should go further than the cubes shadow, as I did a very precise line up on the shadows....though, I could always be wrong, so I won't be too self-confident

Hehe, jpeg compression Probably just the pencil lines...I did it on paper, so I'm quite happy that I actually had the patience to sit and draw those lines and shade it all with pencil, though it's harder to make the shading as accurate as it photoshop.
offcos I fixed some "digitally"

Thx again!

------------------
Joachim
web: http://home.sol.no/~jbarrum/


[This message has been edited by Joachim (edited May 31, 2000).]

[Shorty]

Thanks for the crit Sumaleth - really appriciate it!! I will try to fix the stuff you mentioned.

I had some problems with the shadow from the cube on the left projected on the cube to the right - so it would be great if someone could explain this to me.

-sHORTy-

[Shorty]

Hi Saffron! Thanks for the warm welcome :-)

Yes, I also work at Innerloop together with Micke and Joachim - which is a lot of fun!

I dunnot know anything about drawing though, so I thought that I should follow this class. It is really great that Fred and Spooge is willing to spend their time on this - much appriciated!

-sHORTy-

[Alan]

Thanks for the critique. Now for attempt number 2. One of these days I might be half right.



-Alan

[micke]

Thanks a lot Sumaleth! I'll try again

------------------
-Mikael Noguchi-

http://www.katode.org/noguchi/

[Joachim]

Btw, I did some lineup on the objects and then the light...
I hope I do this right or ? Just thought I could check it for the sake of it, and I found some minor mistakes on the line part, not wrong but more from not being too exact while I lined things up on paper in the first place.
But, if someone have some comments or see something I've done wrong the way I lined this up, please tell..maybe I've misunderstood something.




and if anyone would want it, here's the psd file: http://home.sol.no/~jbarrum/forum/cube2_lines.psd

------------------
Joachim
web: http://home.sol.no/~jbarrum/



[This message has been edited by Joachim (edited May 31, 2000).]

[Sedone]

Thanks for the critique, Sumaleth. I'll redo it after my other homework

[Sumaleth]

Joachim:

The link to the PSD doesn't work so I can't check for sure, but there are two errors that I can see from the linework;

The two VP's for the cone are wider apart than for the main cube yet the cone is slightly further away. We haven't got exact details yet, but for objects that are further away the VP's should be closer together than for objects nearer the camera view. For objects side by side it seems that the VP's should be the same distance apart although i think that only applies when the objects have roughly the same rotation (as they do in your image).

The only implication this has in the image is that the base of the cone is probably distorted compared to the main cube, but not by enough to worry about.

I'll have to see the PSD to see if the shadow edge on the cone is in the right spot, it's too hard to tell from the little images but it doesn't appear to be right.

The other obvious problem was with the cast shadow from the cone across the main cube - on the top the shadow clearly goes all the way across the top of the cube which means you would expect to see the cones shadow continue past the cubes cast shadow (as mention in the previous comments). However, looking at the diagram it doesn't look like the shadow would go that far out.

I'll need to see the PSD to be sure, but I -think- that possibly the pointed end of the cone's cast shadow would end on the top of the cube somewhere.

I'm not sure if it's possible to work out the exact shadow for the cone based on the images that Francis' has posted (which were designed for cubes), but with some clever line work it may be possible to work out how the shadow should cast across the cube. I'm guessing that you'd find the point of the cone's shadow ended about 1/3 of the way aross the top of the cube.

Cheers,
Sumaleth

[Frost]

...

[synj]

how about getting to lesson number 2 already, if this post is gonna linger forever. I'm pretty sure we've got the cubes down, guys.. . .

[Hurri-cane]

LOL....yes....plez change lesson

[Joachim]

Thx for you comments Suma...things have now come clearer to me.

The vanishing points thing. I just did it the way I remembered it from school and after following this thread. But, after you told me the vanishing points of the cone and cube was different I started to think ( I don't usually do that )...I know Francis illustrated that two cubes behind eachother had the same length between each vanishing point, just scaled down, but I didn't think more through it than that.

So, now I know that the two vanishing points have always got the same lenght between them, if you think that the world you make are 360 degrees around..So, when rotating the cube and the vanishing point gets closer to each other or further away, it's just because the picture can't illustrate that it goes around.
So, if you change the distance of the vanishing points, you only change the field of view, right ?

Hehe, I made a little gif anim, in motion it's easier to think about this, and for the fun of it



So, with light...while moving the light up and down on the vertical line it's only the Z position of the light, and moving the line left righ shows were the light is in X position. And the shadowpoint makes you illustrates were the Y position is, which also give you the target of the light..this is for a world light as the sun.....this I knew though, I hope it's correct
But, let's say you want the light to point straight down nomatter were in the world, as a spotlight, how do you line up that ?

I guess everyone on this thread understood all of this allready, but as some artists (I guess) I've always been a bit slow to understand the reasons for everything, just did what I was told and thought looked good, without thinking it really through (I'm lazy that way )
Hehe, atleast I now know that there's a bunch of mistakes on my cubes that is not too easy to spot right away. I think I will have to do another

Sorry for being such a dumb ass....

------------------
Joachim
web: http://home.sol.no/~jbarrum/


[This message has been edited by Joachim (edited May 31, 2000).]

[AliasMoze]

Suma,
When you plot the cast shadows from a cone, all you need are the sides and the point of the cone. You can draw a line from the light source, through the point and onto the ground. From this point, the other two lines can only be drawn one way.



Somebody was also asking about how to plot to cubes that are rotated at different angles. I can draw that up later today if someone wants.

Joachim, just saw your reply. I'll try to do the cone casting a shadow onto another object a little later
------------------
AliasMoze

"That activates my hilarity unit."

[This message has been edited by AliasMoze (edited May 31, 2000).]

[Joachim]

AliazMoze...

Please do AliazMoze!, make an object behing which gets affected by the cone's shadow as well ?



------------------
Joachim
web: http://home.sol.no/~jbarrum/

[Frost]

Joa: Good reasoning. =) Yes, the distance of your VPs (on a cube for instance) on a 2D drawing simply changes the scene FOV, as in a renderer - The closer they are, the higher the FOV and vice-versa... it's also relative and you can play around with them as you wish in your scene.

Anyway, anything I say is disregarded, so, I'll shut up.

See you on ICQ hopefully...

[Sumaleth]

AliasMoze: Actually, working out how a cones cast shadow works was kinda easy, the bit I was wondering about was where the cast shadow falls across another object . Suddenly those last two no-brainer lines become a little more tricky. With a little thought and a lot of construction lines I'm sure its workable though.

Joachim: Thats a great little animation! It shows two things really well;

. Changing the spacing of the VIP's, without rotating the cube, changes the "angle of view" (or "field of vision") of the camera.

It would be interesting to see if there are any formulas for working out the relationship between the FOV and the distance between the VP's but I doubt that there are.

. If you want to rotate the cube, the horizon line must be treated as a circle surrounding the camera rather than a straight line that simply extends out from each side of the page. Note that when the cube is totally in line with the camera that the VP on the right would be out at infinity if it were on the horizon line.

Clearly the process of 2-point perspective is really just a simplification of real perspective and so the placement of two cubes in a scene at different rotations is a *very* complex issue when using this process. I wouldn't be surprised if there were no systems available for doing this totally accurately. So the only way to get it accurate would be to use the top-down projection process that Francis posted.

Anyway, very interesting but probably a little off the track .

Sumaleth

[AliasMoze]

Doh! Sorry, I misunderstand what you were asking for. I'll plot the other ones out later (I'm working)

------------------
AliasMoze
:) :) :) :)
"That activates my hilarity unit."

[Joachim]

Hehe, AliazMoze, I saw you changed the sketch, so then my point disappeared

[This message has been edited by Joachim (edited May 31, 2000).]

[AliasMoze]

I goofed it in my haste the first time. Are we three the only ones left in class?

------------------
AliasMoze
:) :) :) :)
"That activates my hilarity unit."