I created a mesh, then use particles to make grass on it. I just want to take the grass and grass's shadow on render, so I make the mesh's material become invisible (by using Transparent BSDF, alpha is zero).

But when the mesh become transparent, the grass's shadow is disappear too. How can I still get the shadow while the mesh is invisible?

I use Blender 2.70, Cycles Render

The grass's shadow is disappear when the mesh become transparent

  • $\begingroup$ Thank you for fast replay. I tried it, but there is no "Set Alpha" node in my "Add > Converter" menu. May be in 2.7 version it has been deleted or renamed or something? $\endgroup$ – Trung Dong Jul 15 '14 at 16:20
  • $\begingroup$ @user2695076 Make sure you are using composite nodes $\endgroup$ – gandalf3 Jul 15 '14 at 18:41
  • $\begingroup$ What you are looking for is called a "shadow catcher". A transparent plane that receives the shadows of generated objects but is otherwise transparent. Read this blender.stackexchange.com/questions/10650/… and watch this video youtube.com/… $\endgroup$ – user1853 Jul 15 '14 at 23:15
  • $\begingroup$ Wait, I just noticed that the example image is transparent. Do you want the shadows to be rendered over image alpha? Or do you want objects behind the plane to be visible? $\endgroup$ – gandalf3 Jul 15 '14 at 23:21
  • $\begingroup$ @gandalf3 I want the shadows to be rendered over image alpha. $\endgroup$ – Trung Dong Jul 16 '14 at 2:54