In Blender 2.8, within the boundaries of a big rectangle I have several overlapping objects (planes and text) to which I would like to overlay a semitransparent layer of dirt.

Will this work? (a) Create a new plane that with the same dimensions as the big rectangle (b) Assign a .png image of dirt to the new plane (c) Position the new plane over the big rectangle (d) Set the transparency of the new plane as desired

If so, I would appreciate suggestions on how to (i) make the dirt.png image appear in the new plane and (ii) set the transparency of the dirt

Thanks in advance!


Select the plane with the Black and white dirt image and switch its blend mode and shadow mode to "Alpha something", and play with the parameters until you get the look you're looking for.

enter image description here

  • $\begingroup$ What would I do if I want the grime to be darken the picture (like soot) rather than lighten it (like ash)? It seems that the dark parts of the black and white picture become transparent. Is it possible to reverse the effect (so that the white parts are transparent)? $\endgroup$ – vndep Jul 27 '19 at 11:56
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    $\begingroup$ yes, just swap the two inputs in the mix shader, black leads upper signal, white will switch to lower one (and gray will mix both). $\endgroup$ – josh sanfelici Jul 27 '19 at 12:55
  • $\begingroup$ Thanks - that works nicely. Two questions/issues: (a) why when I switch from Shading to Layout, everything goes gray? (b) In Shading, the objects that are not now "dirty" have gone from gray to white. $\endgroup$ – vndep Jul 27 '19 at 14:00
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    $\begingroup$ Please clarify your question. When you switch from Shading to Layout are you stil in "rendered" view mode? Whta does it mean from gray to white? Maybe you could share your file. $\endgroup$ – josh sanfelici Jul 27 '19 at 19:56
  • $\begingroup$ For (a) it turns out to be q question of view mode. For (b) an oversight on my part. $\endgroup$ – vndep Jul 28 '19 at 12:15

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