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+--- Thread: Shadow question (/Thread-Shadow-question)
Shadow question - sl60 - 02-13-2023
If I have a tree on a lawn, for example, and I add a cast shadow on the grass, how can I accurately depict the shadow if it hits a vertical wall and climbs upward?
![[Image: vertical-garden-with-walls-concrete-floo...3-7795.jpg]](https://img.freepik.com/premium-psd/vertical-garden-with-walls-concrete-floors_313313-7795.jpg)
RE: Shadow question - denzjos - 02-13-2023
Make a new layer with a picture from tree, scale it, convert it to BW (Colours / Desaturate) and set the the layer mode Opacity to 60%. If needed, use the 'Perspective Tool' to adjust.
[attachment=9364]
RE: Shadow question - rich2005 - 02-13-2023
I would not worry too much about the shadow, there are lots of variables involved, the position of the light source, distances and angles.
For a made-up situation it might go like this: https://youtu.be/rb_8VJrsb84 duration 1' 40"
RE: Shadow question - sl60 - 02-13-2023
I was thinking of something a bit more realistic like this from Photoshop, but then somehow bending the shadow to climb up the wall.
https://www.youtube.com/watch?v=q_GOfAc3qTE&ab_channel=JasonYadlovski
Also, see this starting at 18:49--this is what I want to do---
https://www.youtube.com/watch?v=HyAqx6VGGnw&list=RDCMUCdv_VnYKlu_gaZa7rpXifEg&index=6&ab_channel=SketchUpSchool
RE: Shadow question - Ofnuts - 02-13-2023
If you look at the geometry of things the shadow (from the sun) of an object on a vertical wall is just the shape of the object, where verticals remain vertical. If the wall isn't perpendicular to the light rays, you get a deformation which is what you would get with the perspective tool. The ground shadow is also a perspective transform. In the following example:
- The shadow on the wall is just the shape of the object, shifted down and with a perspective to match the wall. The bottom is cut where the wall touches the ground (at half the trunk height)
- The shadow on the ground is another perspective transform where: 1) the base of the tree is kept, and 2) it intersects the base of the wall where the wall shadow is cut, and in a place which is roughly at half the trunk height. As you can see from the branches in the top right, this is a very elongated perspective (in a real image you would cut these off of course.
- You can probably do the two perspectives in the other order, for instance if you have strong constraints on the ground shadow.
[attachment=9366]