I created a puppy out of lines and shapes in Illustrator CC. It is rather flat and I am trying to make it somewhat more 3-dimensional, similar to the images created by Disney. Is there a way to do this manually, or is there a program (preferably free) that I could use?)
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The method I would use to create such shading and highlights is to use gradient meshes in Adobe Illustrator. Here's an example showing the kind of effects you can get.
This technique isn't quick or easy, but it's worth learning how to do it. There are's a good tutorial to get you started on the Adobe website: https://helpx.adobe.com/uk/illustrator/how-to/illustrator-growing-gradient-mesh-tomato.html
The essentials are already said in comments, but I can also show something coarse that can be achieved in Photoshop in few minutes. For Disney class results is needed a much more skilled and talented person, one who can imagine the wanted result beforehand. The rest of us waste the time in aimless wandering.
Your image was splitted in several layers (outline, face lines, brown body, black background; your image really had it altough it is invisible in the web browser)
First a dark shade was generated at the dege. A copy of the black backgroud was blurred and then cutted off the exessive part. Proper selection was generatd easily with the intact black background.
Then added a layer for manually brushed shadows and highlights. Very smooth brush was used to spray black and white. The layer has blending mode = hard light. The extras were removed by the eraser.
The result after 5 minutes struggle:
The story above imitates coarsely the methods from the time before the computers. Today the objects often are generated in 3D. For animation the 3D model can have built-in methods to move and deform its shape.
Wihout changing the method, there exists shortcuts. You can
- draw solid black and white lines or dots to the centers of the shadows and the highlights + apply Gaussian Blur filter to get a smooth gradient, if needed. The exessive blur can be erased or deleted by a selection+DEL.
- keep different major shadings in different layers to be able to adjust their opacity separately for different effect depths and for easy redoing in case of errors.
In 3D the shading comes from the rendering software due the selected materials and lights and it adapts automatically when the object moves or deforms its shape.