Is there a way to sample the color at a particular point on the mesh's surface?

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Let's take this cube for example. It has a procedural texture applied on an emission material in cycles (but I'm open to solutions in BI or regardless of the rendering engine).

If I would simplify this question, how would I iterate over surface points and then check if each is black or white?

Is there a way to access the RGB value of a surface point prior to or after rendering? Even a vertex would do if there's no way to access the color at a surface point, but I'm looking for a more flexible solution.

It would be best if this can be achieved without baking to a UV mapped image, but if there's no other way, how would one go about accessing the data then?

  • $\begingroup$ What will you do with these values once you obtain them? Will the goal be another image in Blender or something else? $\endgroup$ – atomicbezierslinger Feb 28 '16 at 18:03
  • $\begingroup$ @atomicbezierslinger, generally I want to generate a new mesh from the texture. let's say sample the white points on the textured mesh with 1000 surface points as vertices and generate a mesh from them. $\endgroup$ – TLousky Feb 28 '16 at 18:26
  • $\begingroup$ This gave a visual [appearance] of a plane with texture raised. All the vertices are still there. Plane with photographs. The original question had a photograph that corresponded with the images in the answer. Noise was present. Your images have no noise. blender.stackexchange.com/questions/16516/… $\endgroup$ – atomicbezierslinger Feb 28 '16 at 19:07
  • $\begingroup$ Thanks @atomicbezierslinger. A displacement map did come to mind of course, but I'm looking for a more controllable, precise and low level solution (that will also be relevenat for non grayscale textures). $\endgroup$ – TLousky Feb 28 '16 at 19:40
  • $\begingroup$ You can evaluate noise, using the mathutils.noise module $\endgroup$ – pink vertex Feb 28 '16 at 23:25

Particle System

  • You can generate cubes or other as particles.
  • Convert them in the modifier panel.
  • Join them into Single Mesh
  • Vertex [Remove Doubles] may produce large surfaces if desired

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Above image. Plane with UV Map Bounds. Particle System Grid Resolution 50. Adjust to Needs.

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Image above. Particle System Texture affects density. Blender Internal Render.

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Image Above. Converted Particles with [Convert] in Edit Mode.

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Image Above. Vertex Remove Doubles with a Tolerance. Only the top surface had Remove Doubles. The original cubes had spaces for sake of explanation

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Above image. Sphere shape which is a high density Cube to Sphere Transform. UV Mapped while in Cube appearance. Thus 6 repeating UV faces even though the repetition is difficult to see.

  • $\begingroup$ Nice one! That definitely helps, as I can then access the particle data directly and use the coordinates. $\endgroup$ – TLousky Feb 28 '16 at 20:15
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    $\begingroup$ Hopefully one candidate for a start. $\endgroup$ – atomicbezierslinger Feb 28 '16 at 20:27
  • $\begingroup$ Hmm, you used a plane and rendered a rectangular density map then. So I guess this will need to be baked on a UV mapped object to work with 3D objects? $\endgroup$ – TLousky Feb 28 '16 at 20:47
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    $\begingroup$ Edit above. Yes UV Map. $\endgroup$ – atomicbezierslinger Feb 28 '16 at 21:18

You can check the RGB values of every pixel in any image opened in the Image Editor, including renderings.

Just render your image and hold left-click on it. You can see the RGBA and HSV values in the bottom of the window.

Note that if your Emission shader has the Strength value over 1.0 the results may differ with the actual texture's values.

  • $\begingroup$ I'm not looking for rendered image pixel values (that is indeed quite simple), but rather for the color values at particular points on the mesh surface. $\endgroup$ – TLousky Feb 28 '16 at 18:32
  • $\begingroup$ Oh, sorry. You said "prior or after render". That was actually a silly answer then :-/ $\endgroup$ – Antonio Buch Feb 28 '16 at 18:35

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