Tutorial: Footprints in the Sand

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sand.jpgPhilippe Roubal has been experimenting with ways to animate footprints in the sand. He published the results of his work in a new tutorial.

Philippe’s method works by applying a displacement texture on a finely subdivided mesh. Next, the texture is masked by a gradient layer that is animated to reveal the footsteps one by one. The result is quite convincing – you will find a sample animation at the bottom of the page.

The result looks quite convincing although I wonder if you really need displacement – would a simple bump map achieve the same effect?

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    • Cubedude04

      Wow this is strange as i found this tutorial on BA today when i was browsing through looking for something else.

    • http://3d-synthesis.com ROUBAL

      Hi ! I must admit that I have not tested with a simple bump mapping. The reason why is that I wanted to use a method allowing to put the camera anywhere, regardless to the distance, the angle and the lighting.

      Ordinary bump map effect often show the trick when you put the camera close to the target, or at a low angle, so as I plan to show the feet in close up in a sequence that I have in mind, I used this method. It needs more computer power, but it is worth it.

      An other thing that pushed me to use real displacement is that when you add your character in the scene, the fake bump (the rim of sand around the foot) will not mask the foot, and the trick will be revealed !

      Obviously, if you only plan to show a large part of the beach from a reasonable distance, simple Nor Bump mapping will be sufficient !

    • Roger

      This technique is great also to show a walking invisible man or dracula as the footprints are made, since you can reveal each footprint as it is made, i.e., by lowering the plane at an angle, it appears as though the person is striking the sand with their heel first.

      Cubedude: Keep a library of these; we still use Disney’s original techniques even today; these are good for the next 50 years or so. See also the wiki Tutorials and Tutorial Links pages.

    • Terence

      Actually, I remember this same technique in an old 3D Studio Max book (actually, the tutorial in that book was also animated footprints, this time in the snow). Just this past week I was thinking about trying it with Blender. Nice job.

    • http://www.blog.ohweb.com.ar Gez

      I think a normal map instead a simple bump would make the trick.
      The normal map can be created using the character’s feet in stride position, cutting them and inverting their normals and extending the outlines to a single plane.

      Anyway, using displacement is better for closeups, as Roubal said.

    • BeBraw

      Nice tutorial! I think that you can replace the gradient mask texture with Blender’s blend procedural texture. Use an empty as map input! Now you can use it to determine its location and it should work as the gradient mask does.

    • http://mke3.net Matt

      Nice! Next challenge is to make it so the heel sinks in first followed by the toes slapping the surface, rather than the footprint ‘sliding’ on in a wipe transition :)

    • http://www.universodegoma.net/ DiThi

      The AVI making step wouldn’t be necessary if material nodes allowed geometry input from other objects

    • http://3d-synthesis.com ROUBAL

      @Matt :

      I think that this effect can be done simply by making speed variations in the animation of the grey mask when making the AVI texture.

      The print must be unmasked in two times, the second time (toes)more progressive than the first(heel).

    • jaycun

      I wonder if the Fluid Simulator could be used to simulate footprints? Set the viscosity to that of mud or sand…set compressibility to 0 and animate a foot walking in the “fluid” for the footprints….bake and then render.

    • http://3d-synthesis.com ROUBAL

      @jaycun

      That’s a very interesting idea! I think that it should work, but I don’t know if one could easily add a texture on the fluid surface if needed.

      Maybe yes, because baked fluids are made of series of meshes…

      It would be fun to make some experiments in this way !

    • http://www.nathandunlap.brickfilms.com/ Nathan

      Wow, that is really cool. Very simple, too. I really like the final result! Thanks for sharing!

      Nathan

    • http://blendernewbies.com Kernon

      @Roubal
      You can definitely add textures to fluids, including video. :)

    • Kop

      Hmm… I wonder if you could make a particle system to cover the ground with sand/snow/whatever, then set it up so that the particles die when an object (like a foot) hits them? It might be more CPU-intensive, but it would be automatic, and the extra processor time might still be less than the time it takes to make the disp map.