Don't know if anyone is interested, but from my old high school 'Geometric Drawing & Perspective' days.....

Seat and Source Shadows.

Determine where the light source is. The seat is the point where the source would hit the ground.

Two simple rules only:

(1) From the source through the point (P).

(2) From the seat through the plan of the point (P'). The 'plan' of the point is where it would hit the ground.



Anyway, nothin' to see here.....keep moving.

I think you're asking too much of people.

like vanishing points in revers, kinda visabling points, thanks saves the diagram

This is great but i have the most problem telling where the source is. I can get a general idea.
Lets take your block for a example. if you remove the line's and look at just the block.
I would have put the shadow about 90 degrees to the left. That would move the source to the far right, instead of the far left where it is now.

I say this because the blocks top and right side seem to be lite equally. The front is the darkest. Therefore the shadow should fall towards the darkest side.

Well i hope i have confused everyone with the mumbled translation of what i was thinking. IT sure sounded better in my skull than in print.

i noticed that people have problem with too blurry shadows or not....this can be solved by analysing the distance oof the source.
And not forget if the source is the sun (parallele light) or if its an electric bulb.
good topic thx Brad

I shaded that block a little to match where I put the source....but yeah, you're right....you'de have to make your best guess. It's a bit hard to tell with the coloured face on that block too. Maybe I should have chosen a plane block.

Anyway, there's no reason that the source couldn't be put in front of the block, casting a shadow somewhat backwards. You could always adjust the lighting on the faces. Or heck, maybe you might be putting a shadow on something you made entirely from scratch.

this is a wonderful thread thank you for posting it i can't wait to read up on all that is said
-matt-

it looks like u have fun with ur colour pencils

You're right Naiko. I didn't point out that this would not be from the sun. For the sun we use 'ambient' rays which are parallel.

If you have something with a shadow already there, you can just do the opposite to find where the source is.

Great Thread---Tut worthy--definately tut worthy. Nice work.

I was keeping up till the ambient rays thing. Not getting the difference.
good info though. Thanks Brad

parallel light: put a line of soldiers in the sun of the desert...all the shadows are parallele, cuz the sun is very far and very big right ?

electric light/the source is tiny and quite close, put 3 persons in the room, in line too, u will have not parallele shadows.
i wish my english bettertho...)

Does this help?

I'm usually not one to argue but 'ambient' is a rather different can of worms.

Amibent light is that generalized lighting not attributable to the direct rays from a specific light source. In the physical world, ambient light is attributable to the reflection of light off of surfaces in the environment. Without ambient light, objects in shadow would be completely black.