How to create a 3D object that has the dimensions (shape) of a shadow

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Hi all,

I don't really know how to describe my problem, and if there is a 'simple' solution for it, but I'll try. I have an object (probably going to limit myself to simple shapes) that cast 2 shadows. I'd like to generate a mesh that is the shape of that shadow. As you can see on the image below, I drew the desired meshes in green.

desired meshes are drawn in green

I've messed around with altering the vertices of my initial mesh, and in some specific cases (objects with no rotation) found a solution, but I haven't found one that's works good enough. Does anyone have an idea that could work?

Thanks in advance, Bart

Answer 1

Best Answer

Answer by Grimmick · Jun 04, 2016 at 03:53 PM

You just want to extrude the shadow like shown in the picture, right?
And the object always casts the shadow on two planes, right?
Are the "light sources" for the shadows modeled as point lights or directional lights?

If so, one possible way to solve it for sufficiently simple objects would be to cast rays onto the planes from the "light source" through every vertex of the objects mesh and then determine the convex hull of those dots (basically throwing a lasso around all dots). The dots on the convex hull are your base points, which you can then extrude.

I found these tutorials very interesting on generating a dynamically generated mesh: https://unity3d.com/learn/tutorials/projects/procedural-cave-generation-tutorial
-> 3. Creating Meshes + 4. 3D Walls

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Answer 2

Answer by Bartvdb · Jun 06, 2016 at 05:09 AM

Thanks for the answer.

Already made the step to use raycast to project my object on to a wall, but was having a little problem with creating the mesh itself. The tutorial you linked helped me with that.

I asked the same question on stack overflow and got more or less the same answer, although yours was more in the lines of what I'm trying to do. If anyone is interested: http://stackoverflow.com/questions/37615715/i-want-to-create-a-mesh-from-a-silhouette

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How to create a 3D object that has the dimensions (shape) of a shadow

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